Invasive non-native plants are species that have been brought into the United Kingdom that have the ability to spread causing damage to the environment, the economy, our health and the way we live. Noxious weeds are native species, which have been deemed to cause a problem to farming productivity.

You must not plant or otherwise cause to grow in the wild any plant listed on schedule 9 of the Wildlife (Northern Ireland) Order 1985.

Invasive plants

If you have invasive plants on land that you own or occupy, you must comply with specific legal responsibilities, including:

• spraying herbicides - see spraying invasive plants with herbicide
• burning invasive plants - see cutting and burning invasive plants
• burial of soil containing invasive plant material - see burying invasive plant material on site
• off-site waste disposal - see disposing of invasive plants and contaminated soil off-site

You do not need to notify anyone about the invasive plants on your land.

Invasive plants are listed in schedule 9 of the Wildlife (Northern Ireland) Order 1985, as amended by section 27 schedule 1 of the Wildlife and Natural Environment Act (Northern Ireland) 2011.

Noxious weeds

Noxious weeds are those that are considered able to cause harm to agriculture. The seven species of 'noxious weed' are:

• common wild oat
• winter wild oat
• spear thistle
• creeping thistle
• broad leafed dock
• curled leafed dock
• common ragwort

If you have any noxious weeds on your land, you are responsible for controlling them. You must prevent them from spreading onto adjoining land.

It is important that you can identify invasive plants on your premises. This will allow you to manage and deal with them in the most appropriate way.

Identifying invasive plants on a site early lets developers assess and cost options for destroying, disposing of and managing them.

Managing land infested by invasive plants in a timely and appropriate way can avoid:

• excessive cost
• potential prosecution and compensation claims
• physical damage to buildings and hard surfaces
• harm to the environment

Identifying Japanese knotweed

Japanese knotweed begins to grow in early spring and can grow in any type of soil, no matter how poor. It can grow as much as 20 centimetres per day, and can reach a height of 1.5 metres by May and three metres by June. It does not produce viable seeds in the United Kingdom, but instead spreads through rhizome (underground root-like stem) fragments and cut stems. Japanese knotweed:

• produces fleshy red tinged shoots when it first breaks through the ground
• has large, heart or spade-shaped green leaves
• has leaves arranged in a zig-zag pattern along the stem
• has a hollow stem, like bamboo
• can form dense clumps that can be several metres deep
• produces clusters of cream flowers towards the end of July
• dies back between September and November, leaving brown stems

Identifying giant hogweed

You should take great care when identifying giant hogweed. Contact with the plant, particularly the sap, can lead to severe blistering and scarring.

Giant hogweed closely resembles native cow parsley or hogweed. It can take four years to reach its full height of three to five metres and flower. Giant hogweed:

• has a reddish purple stem with fine spines that make it appear furry - like a stinging nettle
• has hollow stems
• has spotted leaf stalks
• has leaves up to 1.5 metres wide
• flowers in June and July
• has flower heads that are usually 50 centimetres wide - each flower head is capable of producing 50,000 seeds every year
• has seeds that can stay in the soil for several years before they develop

Identifying Himalayan balsam

Himalayan balsam is often found on river banks, growing up to two metres in height. Each plant lasts for one year and dies at the end of the growing season. Himalayan balsam:

• has reddish coloured stems
• has dark green, lance-shaped leaves with jagged edges
• flowers from June to October
• has large, brightly coloured flowers that are usually in variable shades from purple to pale pink
• can produce around 2,500 seeds per plant each year
• has explosive seed pods that can throw seeds over 6 metres away from the plant

Identifying other invasive plants

Other species of invasive plants in the UK include:

• floating pennywort
• parrot's feather
• creeping water primrose
• New Zealand pigmyweed (also known as Australian swamp stonecrop)
• curly waterweed
• nuttall's waterweed
• Canadian pondweed
• water fern (also known as fairy fern)

To remove invasive plants from your premises or to stop them from spreading, it helps to understand how new plants grow and spread. This will help you decide what action to take.

If you employ a contractor to do the work for you, you should understand what they intend to do and why. This could help you decide what you actually need and could save you money.

How Japanese knotweed spreads

Japanese knotweed does not spread from seeds in Northern Ireland. It is spread when small pieces of the plant or rhizomes (underground root-like stems) are broken off. One piece of rhizome or plant the size of a fingernail can produce a new plant.

Pieces of plant or rhizome can be transported to a new location by:

• water - if the parent plant is close to a river or stream
• moving soil which contains them
• fly-tipping cut or pulled stems

Individual plants can cover several square metres of land, joined up below ground by an extensive rhizome network. Herbicide treatment can be a very effective way of controlling Japanese knotweed, but a lack of regrowth does not mean the underground rhizome is dead. If the soil is disturbed, knotweed often regrows.

How giant hogweed spreads

Giant hogweed produces large, umbrella-like flowers, each of which can produce up to 50,000 seeds. These seeds fall typically within four metres of the parent plant. Seeds can be transported by:

• vehicles - particularly along roads and railways
• water - if the parent plant is close to a river or stream
• footwear
• moving soil which contains them

The seeds can remain dormant in the soil for 15 years. Even if you treat the plants with herbicides and they die, several thousand seeds are waiting in the ground below for the opportunity to take their place. Any control programme needs to continue for several years, including checks for new growth. When managing giant hogweed it is important to maintain a healthy grass sward, either by using selective herbicides or by sowing grass mixes. A dense grass sward helps to prevent giant hogweed seeds from germinating.

Giant hogweed contains sap that is released when the plant is cut or by brushing against the plant. Contact with the sap causes skin to become sensitive to sunlight, resulting in painful blisters which appear up to two days after contact and may reoccur for several years.

How Himalayan balsam spreads

Himalayan balsam plants can produce around 2,500 seeds each year. The seedpods open in such a way that the seeds are thrown up to seven metres away from the parent plant, helping the species to quickly spread. Seeds can also be transported by:

• water - if the parent plant is close to a river or stream
• tracked vehicles
• footwear
• moving soil which contains them

Even if you remove these plants, or treat them with herbicides and they die, several hundred seeds can be waiting in the ground below for the opportunity to take their place. The seeds can survive for several years, so any control programme needs to continue for a couple of years, including checks for new growth.

If you do not manage invasive plants correctly, they will spread over time and they could cause damage to structures, such as building foundations.

If you have invasive plants on your site you should put up signs, where appropriate, to warn employees and the public about the invasive species that are present.

Put up posters in offices and communal areas to explain to employees what the problems are and what they need to do. Include pictures of the invasive plants you have on your site. This is particularly important for giant hogweed, as contact with sap from the plant can lead to skin burns.

Handling Japanese knotweed

Make sure your staff can identify Japanese knotweed rhizomes (underground root-like stems). This can reduce waste costs and improve how you manage Japanese knotweed on-site.

You should minimise the amount of soil containing Japanese knotweed material that you excavate. Soil containing Japanese knotweed material that has been treated can be reused for landscaping the site, but should not be taken off-site, unless to landfill.

You have a choice of herbicides that are effective against Japanese knotweed, depending on your situation - see spraying invasive plants with herbicides.

On development sites you should fence Japanese knotweed where possible, using clear signs so that only appropriately briefed personnel enter the enclosure to deal with the infestation and resulting waste. This includes areas with waste plant material or soil contaminated with Japanese knotweed. The fence should be at least seven metres away from the plants. Put up restricted access signs around these fenced areas. You must not use tracked vehicles within the affected area, and make sure any vehicles leaving the area are pressure washed.

You must never strim areas containing Japanese knotweed. If you are going to clear areas where Japanese knotweed is present, make sure you remove all cut stems - see disposing of invasive plants and contaminated soil off-site.

Do not try to compost Japanese knotweed material - it will produce new plants. You must not put cut plant material directly onto the ground. If you must stockpile cut material, make sure it does not come into contact with soil - for example, by placing it on top of a barrier membrane - see cutting and burning invasive plants.

Keep soil containing Japanese knotweed material separate from clean soil. This will reduce the volume of soil that you need to treat and dispose of.

Handling giant hogweed

When giant hogweed sap comes into contact with skin, it reacts with sunlight and causes chemical skin burns. Giant hogweed sap becomes more toxic as the year progresses and the plant is exposed to more sunlight.

The stem and underside of the leaves have hairs like a stinging nettle. Brushing against giant hogweed can be enough to get sap on your skin.

If you have giant hogweed on your premises, you must ensure that the public and your employees are protected from the hazards of its toxic sap.

You should control giant hogweed before it seeds. You must not use a strimmer on giant hogweed. The sap from the plant may get onto your skin or into your eyes.

If you are going to get close to or handle giant hogweed, you should wear full protective clothing with gloves, a hood and a full-face visor. You should wash down your protective clothing before you take it off.

If you get sap on your skin, cover it to keep it out of the sun. Go indoors immediately and wash the sap off your skin with soap and lots of water.

Treating invasive plants with herbicide can be a very effective method of treatment. You will have to respray. It usually takes at least three years to treat Japanese knotweed until it is dormant. Giant hogweed seeds can continue germinating for 15 years after the last seed fall.

If the plant is in or near to water you must have agreement from the Northern Ireland Environment Agency (NIEA) to use the herbicide. The herbicide must be approved for use in or near water.

The herbicide's effectiveness depends on the type used. An advisor certified by BASIS (the registration, standards and certification scheme for pesticides and fertilisers) will be able to advise you on the most suitable type of herbicide for your situation and when best to apply it.

Find information on pesticide and fertiliser registration, standards and certification.

Giant hogweed and Himalayan balsam both drop large quantities of seeds. A control programme will need to continue for several years, with checks carried out throughout the growing season. If you are trying to eradicate these plants from a riverbank it is important to ensure that any plants upstream are also treated to avoid seeds being washed onto the site.

Japanese knotweed has a large underground network of rhizomes (underground root-like stems). To eradicate the plant you must kill the rhizomes. Picking the right herbicide is essential, as it must travel through the plant and into the rhizome system below. Several herbicides can treat Japanese knotweed successfully - you will need to pick the right herbicide for your situation. Glyphosate is effective because it penetrates through the whole plant.

Using herbicides

The person doing the spraying must hold a certificate of technical competence for herbicide use or work under the direct supervision of a certificate holder. If you plan to spray in or near water, the person carrying out or supervising the spraying must have the appropriate aquatic part of the qualification. The sprayer must also comply with the pesticide product label and meet all of its conditions. Before you spray in or near water you must check that the product is approved for use near water. There are formulations of glyphosate and 2.4-D amine that can be used in or near water and are effective against many invasive plants.

You can get a certificate of technical competence by attending a short course at an agricultural college or similar institution.

For herbicide to be effective, make sure you use it at the correct time of year:

• Japanese knotweed is best sprayed in late summer from flowering onwards.
• Giant hogweed should be sprayed in April or May, before the plants flower.
• Himalayan balsam should be sprayed in spring before flowering, but strimming or hand pulling should be your preferred option for control of this plant.

You must follow the guidance in the statutory code of practice for plant protection products. If you follow its advice you should stay within the law.

Download guidance on the safe use of pesticides for non-agricultural purposes (PDF, 137K).

If the invasive plants are near a watercourse, you should not use herbicides as the first option. If you are planning to use herbicide in or near to a watercourse, you must consult the NIEA.

You must also carry out a Control of Substances Hazardous to Health (COSHH) assessment for any activities that involve herbicides.

Dispose of waste herbicides correctly

You must make sure that all your waste is stored, transported and disposed of safely. Waste herbicides are likely to be classed as hazardous waste. You must keep this separate from other waste.

Herbicide containers must either be rinsed or handled as herbicides. Check product labels to see if your waste containers should be rinsed. Water used for rinsing empty containers is classed as dilute pesticides or biocides. You may need a groundwater authorisation, registered waste exemption or trade effluent consent to dispose of this - see pesticides and biocides.

Clearing the leaves and stems of Japanese knotweed or giant hogweed that are above ground and then removing soil contaminated with roots, rhizomes (underground root-like stems) and seeds can provide faster results than just spraying with herbicide.

Try to minimise the amount of waste you generate that contains invasive plants, or their seeds and rhizomes. Any waste you do produce should be treated on site where possible.

Any waste that is taken off site must be taken by a licensed waste carrier and must go to a suitably authorised landfill site.

Plant material can be buried deep on the site where it is produced, as long as it does not interfere with the water table - see burying invasive plant material on site.

You should not remove soil from river banks, as this can cause water pollution. If you are planning to carry out work near a river you should contact the Northern Ireland Environment Agency (NIEA).

If your site floods, the seeds will be spread further across the site, so you will need to manage a larger area.

Digging up giant hogweed

To clear ground contaminated with giant hogweed, you may need to remove soil up to four metres away from the plants and to a depth of 0.5 metres. You will need to check for regrowth regularly. You should spray regrowth with the herbicide glyphosate before the plants flower.

Digging up Japanese knotweed

The rhizome system beneath a stand of Japanese knotweed can be over four metres deep and could extend for at least seven metres around the stand. If you are going to dig out the rhizome system you will need to remove all of the plant material. You should use the rhizome identification guide in the knotweed code of practice, or ask a specialist, to help you identify the plant material.

You will need to check any cleared areas regularly for regrowth. You can spray any regrowth with herbicide.

Digging up Himalayan balsam

To clear ground contaminated with Himalayan balsam, you may need to remove soil up to six metres from the parent plant and to a depth of 0.5 metres. You should not remove soil while the seed pods are present. You will need to check for regrowth regularly. You should pull by hand or strim regrowth before the plants flower.

However, as seeds remain viable in the soil for several years, annual cutting, mowing or grazing or annual herbicide treatment during the spring growing season can be an effective control for this plant. You must also carry out follow up checks for late germinating seeds.

What you must do when digging up invasive plants

Never stockpile contaminated soil or plant material within ten metres of a watercourse, and it should not be stockpiled within seven metres of your site boundary.

Collect any water you use for cleaning vehicles that are used in contaminated areas. If it is contaminated with seeds or plant material, you must not discharge it to a watercourse. You could treat the water by passing it through a settlement tank to remove any soil before passing it through a very fine mesh sieve to remove seeds or plant material. Settlement alone may not be adequate because seeds and plant material float.

You may be able to deposit material sieved from water used for vehicle washing in a controlled area on your land and monitor it for regrowth. You should speak to the NIEA to determine your best option.

See preventing water pollution and discharging trade effluent.

Good practice tips when digging up invasive plants

• You should clearly mark out any areas of your land that contain invasive plants. Fence them off until you intend to clear them. Put the fence at least seven metres away from the plants to contain any contaminated soil or roots.
• When you clear contaminated areas, take care to ensure contaminated soil, seeds and plant material are not spread to unaffected areas.
• Limit the use of tracked machinery where possible. Seeds and plant material can get caught in the tracks and moved around the area.
• If you are developing your land, consider creating a haul road using a strong geotextile overlain with hardcore as a base for vehicles to travel on.
• Cover all lorries, dumpers or haulage vehicles carrying contaminated soil or plant material.
• Thoroughly clean tracked machinery when it leaves contaminated areas of the site. Do this within a designated area that is as close as possible to the contaminated area on which the machinery has been working. Always carry out a visual inspection of wheel arches and tracks before the vehicle leaves the site.
• Look out for regrowth by roads and areas where vehicles have been parked or cleaned. Spray any regrowth with herbicide if required.
• If you are working between November and March in an area where invasive plants are known to be present, look for dead canes from the previous year to identify infected areas. Even if there is no growth evident above ground, seeds from giant hogweed and Himalayan balsam, and Japanese knotweed rhizome will still be present. Try to inspect a development site for evidence of invasive species before it is cleared.

Cutting down or digging up invasive plants and burning the waste plant material can be a useful, low-tech means of control. It can reduce the volume of waste that you need to dispose of off site.

Cutting invasive plants

Cutting Japanese knotweed will, over time, weaken the plant, but it will not kill the rhizomes (underground root-like stems). It can be used as part of other control practices. You must handle and dispose of cut plant material carefully. Burning alone may not be sufficient to kill the plant material. You should place burnt material on top of a membrane and monitor it for regrowth. You must not use a strimmer on Japanese knotweed.

Cutting giant hogweed before the plants flower will help to prevent further seeds being deposited on the ground. This is an effective way of removing these species but it can take many years. You must not use a strimmer on giant hogweed. You must avoid contact with giant hogweed, particularly its sap, as it can cause chemical skin burns. You should wear full protective clothing when working near it or handling it.

Pulling up Himalayan balsam before the plants flower is the most effective method of control. Do not cut the plants before they flower as this can result in a more bushy plant that produces more flowers. The best time to cut is late May. Cut the plant below the first nodule.

Burning invasive plants

If you burn waste in the open, you may require a waste management licence or exemption.

You may qualify for a paragraph 30 exemption to burn certain waste plant tissue and untreated wood if you:

• burn the waste at the place where it was produced
• burn no more than 10 tonnes in a 24-hour period

If you have an exemption, you must comply with the exemption conditions and register this exemption with the Northern Ireland Environment Agency (NIEA).

You must also ensure that your activity does not:

• endanger human health or cause pollution to water, air or soil
• constitute a risk to plants or animals
• cause a nuisance, eg in terms of noise or odour
• adversely affect the countryside or places of special interest

You must notify the NIEA at least a week before you intend burning plant material. You should also notify your district council environmental health officer before you begin burning plant material.

If you burn waste in an incinerator or other similar plant, you may need a pollution prevention and control permit - see burning waste.

Good practice for burning invasive plants

Burning plant material should only give rise to white smoke.

Tell the local fire brigade before you begin burning and again when you finish, so that they are not called out unnecessarily.

You can leave cut stems to dry out in the sun rather than burning them. Make sure you place cut Japanese knotweed and Himalayan balsam material on a membrane and not in direct contact with the ground.

Giant hogweed sap remains toxic after the plant has been cut down. Do not leave cut stems where they could harm people or livestock.

You should try to minimise the amount of waste you generate that contains invasive plants or their seeds, roots and rhizomes (underground root-like stems). Any waste you do produce should be treated on site where possible.

Any waste taken off site must be taken by a licensed waste carrier and go to a suitably authorised landfill site.

What you must do

When you transport invasive plants and soil contaminated with invasive plants, make sure that the vehicle is covered or sheeted so that seeds and plant material cannot blow away. If you allow contaminated soil or plant material to escape, you could be prosecuted and fined.

You must have waste transfer notes (WTNs) for any material leaving your site. You must list any material that contains invasive plants or their seeds on the WTN. Your waste carrier can only take the waste containing invasive weeds to sites authorised to accept it. Plant material, or soil containing plant material or seeds, is likely to be classed as non-hazardous waste - this is a different category from inert waste.

There is a duty of care for waste that affects all businesses. You must make sure that:

• your waste is stored, handled, recycled or disposed of safely and legally by licensed individuals or businesses
• you record all transfers of waste between your business and another business - using a WTN
• you keep all WTNs, signed by both businesses, for at least two years
• you record any transfer of hazardous waste between your business and another business using a consignment note
• you keep all consignment notes, signed by both businesses, for at least three years

You must take waste plant material or contaminated soil to a site that has a pollution prevention and control permit or waste management licence.

The conditions of the permit or licence must allow the disposal of invasive plants at the site. You should check with the waste site in advance to make sure they can accept material containing invasive plants.

The waste site may need notice so that an area can be prepared. For example, a landfill site will need an area away from the landfill liner for material containing invasive plants.

Tax relief for disposing of soil containing Japanese knotweed

Land remediation relief (LRR) is a corporation tax relief scheme introduced to help bring land that has been ruined by various industrial uses or long-term neglect back into productive use. You may be able to claim LRR for removing contamination arising from Japanese knotweed. You will not be able to claim LRR if disposing of material containing Japanese knotweed to landfill - find guidance on land remediation relief.

Invasive non-native plants are species that have been brought into the United Kingdom that have the ability to spread causing damage to the environment, the economy, our health and the way we live. Noxious weeds are native species, which have been deemed to cause a problem to farming productivity.

You must not plant or otherwise cause to grow in the wild any plant listed on schedule 9 of the Wildlife (Northern Ireland) Order 1985.

Invasive plants

If you have invasive plants on land that you own or occupy, you must comply with specific legal responsibilities, including:

• spraying herbicides - see spraying invasive plants with herbicide
• burning invasive plants - see cutting and burning invasive plants
• burial of soil containing invasive plant material - see burying invasive plant material on site
• off-site waste disposal - see disposing of invasive plants and contaminated soil off-site

You do not need to notify anyone about the invasive plants on your land.

Invasive plants are listed in schedule 9 of the Wildlife (Northern Ireland) Order 1985, as amended by section 27 schedule 1 of the Wildlife and Natural Environment Act (Northern Ireland) 2011.

Noxious weeds

Noxious weeds are those that are considered able to cause harm to agriculture. The seven species of 'noxious weed' are:

• common wild oat
• winter wild oat
• spear thistle
• creeping thistle
• broad leafed dock
• curled leafed dock
• common ragwort

If you have any noxious weeds on your land, you are responsible for controlling them. You must prevent them from spreading onto adjoining land.

It is important that you can identify invasive plants on your premises. This will allow you to manage and deal with them in the most appropriate way.

Identifying invasive plants on a site early lets developers assess and cost options for destroying, disposing of and managing them.

Managing land infested by invasive plants in a timely and appropriate way can avoid:

• excessive cost
• potential prosecution and compensation claims
• physical damage to buildings and hard surfaces
• harm to the environment

Identifying Japanese knotweed

Japanese knotweed begins to grow in early spring and can grow in any type of soil, no matter how poor. It can grow as much as 20 centimetres per day, and can reach a height of 1.5 metres by May and three metres by June. It does not produce viable seeds in the United Kingdom, but instead spreads through rhizome (underground root-like stem) fragments and cut stems. Japanese knotweed:

• produces fleshy red tinged shoots when it first breaks through the ground
• has large, heart or spade-shaped green leaves
• has leaves arranged in a zig-zag pattern along the stem
• has a hollow stem, like bamboo
• can form dense clumps that can be several metres deep
• produces clusters of cream flowers towards the end of July
• dies back between September and November, leaving brown stems

Identifying giant hogweed

You should take great care when identifying giant hogweed. Contact with the plant, particularly the sap, can lead to severe blistering and scarring.

Giant hogweed closely resembles native cow parsley or hogweed. It can take four years to reach its full height of three to five metres and flower. Giant hogweed:

• has a reddish purple stem with fine spines that make it appear furry - like a stinging nettle
• has hollow stems
• has spotted leaf stalks
• has leaves up to 1.5 metres wide
• flowers in June and July
• has flower heads that are usually 50 centimetres wide - each flower head is capable of producing 50,000 seeds every year
• has seeds that can stay in the soil for several years before they develop

Identifying Himalayan balsam

Himalayan balsam is often found on river banks, growing up to two metres in height. Each plant lasts for one year and dies at the end of the growing season. Himalayan balsam:

• has reddish coloured stems
• has dark green, lance-shaped leaves with jagged edges
• flowers from June to October
• has large, brightly coloured flowers that are usually in variable shades from purple to pale pink
• can produce around 2,500 seeds per plant each year
• has explosive seed pods that can throw seeds over 6 metres away from the plant

Identifying other invasive plants

Other species of invasive plants in the UK include:

• floating pennywort
• parrot's feather
• creeping water primrose
• New Zealand pigmyweed (also known as Australian swamp stonecrop)
• curly waterweed
• nuttall's waterweed
• Canadian pondweed
• water fern (also known as fairy fern)

To remove invasive plants from your premises or to stop them from spreading, it helps to understand how new plants grow and spread. This will help you decide what action to take.

If you employ a contractor to do the work for you, you should understand what they intend to do and why. This could help you decide what you actually need and could save you money.

How Japanese knotweed spreads

Japanese knotweed does not spread from seeds in Northern Ireland. It is spread when small pieces of the plant or rhizomes (underground root-like stems) are broken off. One piece of rhizome or plant the size of a fingernail can produce a new plant.

Pieces of plant or rhizome can be transported to a new location by:

• water - if the parent plant is close to a river or stream
• moving soil which contains them
• fly-tipping cut or pulled stems

Individual plants can cover several square metres of land, joined up below ground by an extensive rhizome network. Herbicide treatment can be a very effective way of controlling Japanese knotweed, but a lack of regrowth does not mean the underground rhizome is dead. If the soil is disturbed, knotweed often regrows.

How giant hogweed spreads

Giant hogweed produces large, umbrella-like flowers, each of which can produce up to 50,000 seeds. These seeds fall typically within four metres of the parent plant. Seeds can be transported by:

• vehicles - particularly along roads and railways
• water - if the parent plant is close to a river or stream
• footwear
• moving soil which contains them

The seeds can remain dormant in the soil for 15 years. Even if you treat the plants with herbicides and they die, several thousand seeds are waiting in the ground below for the opportunity to take their place. Any control programme needs to continue for several years, including checks for new growth. When managing giant hogweed it is important to maintain a healthy grass sward, either by using selective herbicides or by sowing grass mixes. A dense grass sward helps to prevent giant hogweed seeds from germinating.

Giant hogweed contains sap that is released when the plant is cut or by brushing against the plant. Contact with the sap causes skin to become sensitive to sunlight, resulting in painful blisters which appear up to two days after contact and may reoccur for several years.

How Himalayan balsam spreads

Himalayan balsam plants can produce around 2,500 seeds each year. The seedpods open in such a way that the seeds are thrown up to seven metres away from the parent plant, helping the species to quickly spread. Seeds can also be transported by:

• water - if the parent plant is close to a river or stream
• tracked vehicles
• footwear
• moving soil which contains them

Even if you remove these plants, or treat them with herbicides and they die, several hundred seeds can be waiting in the ground below for the opportunity to take their place. The seeds can survive for several years, so any control programme needs to continue for a couple of years, including checks for new growth.

If you do not manage invasive plants correctly, they will spread over time and they could cause damage to structures, such as building foundations.

If you have invasive plants on your site you should put up signs, where appropriate, to warn employees and the public about the invasive species that are present.

Put up posters in offices and communal areas to explain to employees what the problems are and what they need to do. Include pictures of the invasive plants you have on your site. This is particularly important for giant hogweed, as contact with sap from the plant can lead to skin burns.

Handling Japanese knotweed

Make sure your staff can identify Japanese knotweed rhizomes (underground root-like stems). This can reduce waste costs and improve how you manage Japanese knotweed on-site.

You should minimise the amount of soil containing Japanese knotweed material that you excavate. Soil containing Japanese knotweed material that has been treated can be reused for landscaping the site, but should not be taken off-site, unless to landfill.

You have a choice of herbicides that are effective against Japanese knotweed, depending on your situation - see spraying invasive plants with herbicides.

On development sites you should fence Japanese knotweed where possible, using clear signs so that only appropriately briefed personnel enter the enclosure to deal with the infestation and resulting waste. This includes areas with waste plant material or soil contaminated with Japanese knotweed. The fence should be at least seven metres away from the plants. Put up restricted access signs around these fenced areas. You must not use tracked vehicles within the affected area, and make sure any vehicles leaving the area are pressure washed.

You must never strim areas containing Japanese knotweed. If you are going to clear areas where Japanese knotweed is present, make sure you remove all cut stems - see disposing of invasive plants and contaminated soil off-site.

Do not try to compost Japanese knotweed material - it will produce new plants. You must not put cut plant material directly onto the ground. If you must stockpile cut material, make sure it does not come into contact with soil - for example, by placing it on top of a barrier membrane - see cutting and burning invasive plants.

Keep soil containing Japanese knotweed material separate from clean soil. This will reduce the volume of soil that you need to treat and dispose of.

Handling giant hogweed

When giant hogweed sap comes into contact with skin, it reacts with sunlight and causes chemical skin burns. Giant hogweed sap becomes more toxic as the year progresses and the plant is exposed to more sunlight.

The stem and underside of the leaves have hairs like a stinging nettle. Brushing against giant hogweed can be enough to get sap on your skin.

If you have giant hogweed on your premises, you must ensure that the public and your employees are protected from the hazards of its toxic sap.

You should control giant hogweed before it seeds. You must not use a strimmer on giant hogweed. The sap from the plant may get onto your skin or into your eyes.

If you are going to get close to or handle giant hogweed, you should wear full protective clothing with gloves, a hood and a full-face visor. You should wash down your protective clothing before you take it off.

If you get sap on your skin, cover it to keep it out of the sun. Go indoors immediately and wash the sap off your skin with soap and lots of water.

Treating invasive plants with herbicide can be a very effective method of treatment. You will have to respray. It usually takes at least three years to treat Japanese knotweed until it is dormant. Giant hogweed seeds can continue germinating for 15 years after the last seed fall.

If the plant is in or near to water you must have agreement from the Northern Ireland Environment Agency (NIEA) to use the herbicide. The herbicide must be approved for use in or near water.

The herbicide's effectiveness depends on the type used. An advisor certified by BASIS (the registration, standards and certification scheme for pesticides and fertilisers) will be able to advise you on the most suitable type of herbicide for your situation and when best to apply it.

Find information on pesticide and fertiliser registration, standards and certification.

Giant hogweed and Himalayan balsam both drop large quantities of seeds. A control programme will need to continue for several years, with checks carried out throughout the growing season. If you are trying to eradicate these plants from a riverbank it is important to ensure that any plants upstream are also treated to avoid seeds being washed onto the site.

Japanese knotweed has a large underground network of rhizomes (underground root-like stems). To eradicate the plant you must kill the rhizomes. Picking the right herbicide is essential, as it must travel through the plant and into the rhizome system below. Several herbicides can treat Japanese knotweed successfully - you will need to pick the right herbicide for your situation. Glyphosate is effective because it penetrates through the whole plant.

Using herbicides

The person doing the spraying must hold a certificate of technical competence for herbicide use or work under the direct supervision of a certificate holder. If you plan to spray in or near water, the person carrying out or supervising the spraying must have the appropriate aquatic part of the qualification. The sprayer must also comply with the pesticide product label and meet all of its conditions. Before you spray in or near water you must check that the product is approved for use near water. There are formulations of glyphosate and 2.4-D amine that can be used in or near water and are effective against many invasive plants.

You can get a certificate of technical competence by attending a short course at an agricultural college or similar institution.

For herbicide to be effective, make sure you use it at the correct time of year:

• Japanese knotweed is best sprayed in late summer from flowering onwards.
• Giant hogweed should be sprayed in April or May, before the plants flower.
• Himalayan balsam should be sprayed in spring before flowering, but strimming or hand pulling should be your preferred option for control of this plant.

You must follow the guidance in the statutory code of practice for plant protection products. If you follow its advice you should stay within the law.

Download guidance on the safe use of pesticides for non-agricultural purposes (PDF, 137K).

If the invasive plants are near a watercourse, you should not use herbicides as the first option. If you are planning to use herbicide in or near to a watercourse, you must consult the NIEA.

You must also carry out a Control of Substances Hazardous to Health (COSHH) assessment for any activities that involve herbicides.

Dispose of waste herbicides correctly

You must make sure that all your waste is stored, transported and disposed of safely. Waste herbicides are likely to be classed as hazardous waste. You must keep this separate from other waste.

Herbicide containers must either be rinsed or handled as herbicides. Check product labels to see if your waste containers should be rinsed. Water used for rinsing empty containers is classed as dilute pesticides or biocides. You may need a groundwater authorisation, registered waste exemption or trade effluent consent to dispose of this - see pesticides and biocides.

Clearing the leaves and stems of Japanese knotweed or giant hogweed that are above ground and then removing soil contaminated with roots, rhizomes (underground root-like stems) and seeds can provide faster results than just spraying with herbicide.

Try to minimise the amount of waste you generate that contains invasive plants, or their seeds and rhizomes. Any waste you do produce should be treated on site where possible.

Any waste that is taken off site must be taken by a licensed waste carrier and must go to a suitably authorised landfill site.

Plant material can be buried deep on the site where it is produced, as long as it does not interfere with the water table - see burying invasive plant material on site.

You should not remove soil from river banks, as this can cause water pollution. If you are planning to carry out work near a river you should contact the Northern Ireland Environment Agency (NIEA).

If your site floods, the seeds will be spread further across the site, so you will need to manage a larger area.

Digging up giant hogweed

To clear ground contaminated with giant hogweed, you may need to remove soil up to four metres away from the plants and to a depth of 0.5 metres. You will need to check for regrowth regularly. You should spray regrowth with the herbicide glyphosate before the plants flower.

Digging up Japanese knotweed

The rhizome system beneath a stand of Japanese knotweed can be over four metres deep and could extend for at least seven metres around the stand. If you are going to dig out the rhizome system you will need to remove all of the plant material. You should use the rhizome identification guide in the knotweed code of practice, or ask a specialist, to help you identify the plant material.

You will need to check any cleared areas regularly for regrowth. You can spray any regrowth with herbicide.

Digging up Himalayan balsam

To clear ground contaminated with Himalayan balsam, you may need to remove soil up to six metres from the parent plant and to a depth of 0.5 metres. You should not remove soil while the seed pods are present. You will need to check for regrowth regularly. You should pull by hand or strim regrowth before the plants flower.

However, as seeds remain viable in the soil for several years, annual cutting, mowing or grazing or annual herbicide treatment during the spring growing season can be an effective control for this plant. You must also carry out follow up checks for late germinating seeds.

What you must do when digging up invasive plants

Never stockpile contaminated soil or plant material within ten metres of a watercourse, and it should not be stockpiled within seven metres of your site boundary.

Collect any water you use for cleaning vehicles that are used in contaminated areas. If it is contaminated with seeds or plant material, you must not discharge it to a watercourse. You could treat the water by passing it through a settlement tank to remove any soil before passing it through a very fine mesh sieve to remove seeds or plant material. Settlement alone may not be adequate because seeds and plant material float.

You may be able to deposit material sieved from water used for vehicle washing in a controlled area on your land and monitor it for regrowth. You should speak to the NIEA to determine your best option.

See preventing water pollution and discharging trade effluent.

Good practice tips when digging up invasive plants

• You should clearly mark out any areas of your land that contain invasive plants. Fence them off until you intend to clear them. Put the fence at least seven metres away from the plants to contain any contaminated soil or roots.
• When you clear contaminated areas, take care to ensure contaminated soil, seeds and plant material are not spread to unaffected areas.
• Limit the use of tracked machinery where possible. Seeds and plant material can get caught in the tracks and moved around the area.
• If you are developing your land, consider creating a haul road using a strong geotextile overlain with hardcore as a base for vehicles to travel on.
• Cover all lorries, dumpers or haulage vehicles carrying contaminated soil or plant material.
• Thoroughly clean tracked machinery when it leaves contaminated areas of the site. Do this within a designated area that is as close as possible to the contaminated area on which the machinery has been working. Always carry out a visual inspection of wheel arches and tracks before the vehicle leaves the site.
• Look out for regrowth by roads and areas where vehicles have been parked or cleaned. Spray any regrowth with herbicide if required.
• If you are working between November and March in an area where invasive plants are known to be present, look for dead canes from the previous year to identify infected areas. Even if there is no growth evident above ground, seeds from giant hogweed and Himalayan balsam, and Japanese knotweed rhizome will still be present. Try to inspect a development site for evidence of invasive species before it is cleared.

Cutting down or digging up invasive plants and burning the waste plant material can be a useful, low-tech means of control. It can reduce the volume of waste that you need to dispose of off site.

Cutting invasive plants

Cutting Japanese knotweed will, over time, weaken the plant, but it will not kill the rhizomes (underground root-like stems). It can be used as part of other control practices. You must handle and dispose of cut plant material carefully. Burning alone may not be sufficient to kill the plant material. You should place burnt material on top of a membrane and monitor it for regrowth. You must not use a strimmer on Japanese knotweed.

Cutting giant hogweed before the plants flower will help to prevent further seeds being deposited on the ground. This is an effective way of removing these species but it can take many years. You must not use a strimmer on giant hogweed. You must avoid contact with giant hogweed, particularly its sap, as it can cause chemical skin burns. You should wear full protective clothing when working near it or handling it.

Pulling up Himalayan balsam before the plants flower is the most effective method of control. Do not cut the plants before they flower as this can result in a more bushy plant that produces more flowers. The best time to cut is late May. Cut the plant below the first nodule.

Burning invasive plants

If you burn waste in the open, you may require a waste management licence or exemption.

You may qualify for a paragraph 30 exemption to burn certain waste plant tissue and untreated wood if you:

• burn the waste at the place where it was produced
• burn no more than 10 tonnes in a 24-hour period

If you have an exemption, you must comply with the exemption conditions and register this exemption with the Northern Ireland Environment Agency (NIEA).

You must also ensure that your activity does not:

• endanger human health or cause pollution to water, air or soil
• constitute a risk to plants or animals
• cause a nuisance, eg in terms of noise or odour
• adversely affect the countryside or places of special interest

You must notify the NIEA at least a week before you intend burning plant material. You should also notify your district council environmental health officer before you begin burning plant material.

If you burn waste in an incinerator or other similar plant, you may need a pollution prevention and control permit - see burning waste.

Good practice for burning invasive plants

Burning plant material should only give rise to white smoke.

Tell the local fire brigade before you begin burning and again when you finish, so that they are not called out unnecessarily.

You can leave cut stems to dry out in the sun rather than burning them. Make sure you place cut Japanese knotweed and Himalayan balsam material on a membrane and not in direct contact with the ground.

Giant hogweed sap remains toxic after the plant has been cut down. Do not leave cut stems where they could harm people or livestock.

You should try to minimise the amount of waste you generate that contains invasive plants or their seeds, roots and rhizomes (underground root-like stems). Any waste you do produce should be treated on site where possible.

Any waste taken off site must be taken by a licensed waste carrier and go to a suitably authorised landfill site.

What you must do

When you transport invasive plants and soil contaminated with invasive plants, make sure that the vehicle is covered or sheeted so that seeds and plant material cannot blow away. If you allow contaminated soil or plant material to escape, you could be prosecuted and fined.

You must have waste transfer notes (WTNs) for any material leaving your site. You must list any material that contains invasive plants or their seeds on the WTN. Your waste carrier can only take the waste containing invasive weeds to sites authorised to accept it. Plant material, or soil containing plant material or seeds, is likely to be classed as non-hazardous waste - this is a different category from inert waste.

There is a duty of care for waste that affects all businesses. You must make sure that:

• your waste is stored, handled, recycled or disposed of safely and legally by licensed individuals or businesses
• you record all transfers of waste between your business and another business - using a WTN
• you keep all WTNs, signed by both businesses, for at least two years
• you record any transfer of hazardous waste between your business and another business using a consignment note
• you keep all consignment notes, signed by both businesses, for at least three years

You must take waste plant material or contaminated soil to a site that has a pollution prevention and control permit or waste management licence.

The conditions of the permit or licence must allow the disposal of invasive plants at the site. You should check with the waste site in advance to make sure they can accept material containing invasive plants.

The waste site may need notice so that an area can be prepared. For example, a landfill site will need an area away from the landfill liner for material containing invasive plants.

Tax relief for disposing of soil containing Japanese knotweed

Land remediation relief (LRR) is a corporation tax relief scheme introduced to help bring land that has been ruined by various industrial uses or long-term neglect back into productive use. You may be able to claim LRR for removing contamination arising from Japanese knotweed. You will not be able to claim LRR if disposing of material containing Japanese knotweed to landfill - find guidance on land remediation relief.