Public information on invasive species in Wales Giant hogweed Scientific name: Heracleum mantegazzianum Also known as: Cartwheel Flower, Giant Cow Parsnip, Efwr Enfawr Key Facts • Giant hogweed is a highly invasive plant that can grow up to 5m tall with 1.5m wide leaves and 80cm flowering umbels. Do not touch – sap causes blistering of the skin. • Giant hogweed is listed under schedule 9 of the Wildlife and Countryside Act 1981. It is an offence to plant or cause this species to grow in the wild. • The plant material is also classified as ‘controlled waste’ under the Environmental Protection Act 1990. • Giant hogweed was introduced as an ornamental plant to the British Isles in the 19th century from South West Asia. • It is found occasionally throughout Wales but mainly in the east and south west by streams and rivers and along roadsides. • The plant is spread by seed transported by both wind and water. Description Giant hogweed is an impressive plant, related to cow parsley, which can grow up to 5m tall. It produces large umbrella-shaped clusters of white flowers in June and July up to 80cm across. Lifecycle The plant is a biannual or short-lived perennial, forming a rosette of leaves in the first year and flowering in the second year onwards. Small plants may stay as rosettes of leaves for up to 4 years. The plant dies back in the autumn and survives over winter as a large fleshy tap root. The plant produces around 50,000 seeds each year which can remain viable for up to 15 years. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 1st year Seedlings emerge Grows as a rosette of leaves 2nd year onwards Stem starts to elongate Flowering Seed produced All years Plant dies back and becomes dormant Identification © Crown copyright 2009 GBNNSS Leaves – Dark green deeply divided leaves, spiked at the ends, up to 1.5m wide and 1.3m long with reddish purple spotted leaf stalks. Bristles occur on the underside of the leaves. © Crown copyright 2009 GBNNSS Stem – Reddish purple blotchy and ribbed with sharp bristles usually unbranched. The stem is up to 5 to 10cm in diameter and hollow. Seeds – These are flattened and oval with dark stripes, two on one side and Flowers – White flowers with petals up to 12mm long and arranged four on the reverse, approximately 10mm in flat topped umbrella shaped clusters (umbels). These umbels can long and 7mm wide. be up to 80cm across. Lookalikes There are many other white flowered umbellifers similar in looks to Giant hogweed; such as Common hogweed (Heracleum sphondylium) Cow parsley (Anthriscus sylvestris), Wild angelica (Angelica sylvestris) and Hemlock (Conium maculatum). But it is difficult to confuse giant hogweed with any other plant because of its size, even early in the season, as its leaves will be considerably larger than any other leaves. Giant hogweed is quite distinctive even from its nearest relative Common hogweed, due to its deeply lobed, spikey leaves. Where it is found in Wales It is found occasionally throughout Wales but mainly in the east and south west by streams and rivers and along roadsides. Each plant produces up to 50,000 seeds and these can be spread by water especially when in flood and can rapidly colonise bare areas of bank. Seeds can also be spread by humans through them sticking to car tyres or attaching to clothing and through picking of umbels (seed heads) for decoration purposes. Seeds can also attach to animal fur. Seeds can be dispersed further if blown across frozen or snowy surfaces. Why is it a concern? Giant hogweed is very competitive because of its large size and its rapid growth rate. It outcompetes native vegetation for space and resources. When the plant dies back in the winter it leaves bare areas which are more susceptible to erosion, this can lead to large sections of river bank being eroded. It can be invasive, producing large numbers of seed every year which can survive in the soil for up to 15 years. The sap of Giant hogweed contains a toxic chemical which sensitises the skin and leads to severe blistering, when exposed to sunlight. This reaction can reoccur for many years. © Crown copyright 2009 GBNNSS Legislation and responsibilities Giant hogweed is listed under schedule 9 of the Wildlife and Countryside Act 1981. It is an offence to plant this species or to cause it to grow in the wild. There is no obligation to eradicate this species from your land or to report its presence to anyone. However, if this species spreads to the wild or to a neighbour’s property then you could be liable. The plant material is also classified as ‘controlled waste’ under the Environmental Protection Act 1990. Plant material can only be transported and disposed of by someone licenced. Natural Resources Wales holds a register of licence holders see https://www.wastecarriersregistration.naturalresourceswales.gov.uk/cy/registrations/search Management Control Options WARNING – Giant hogweed contains sap that is released when the plant is touched or cut. Contact with the sap causes the skin to become sensitive to sunlight leading to painful blisters, this reaction may occur for several years. Before working with giant hogweed full protective clothing (overalls, gloves, goggles and hat) must be worn to stop any sap from getting on to skin. There are several options for control both chemical and non-chemical. The aim is to control existing plants, prevent seed return and prevent movement of any material off site. The site will need to be revisited annually in the spring as new plants could regenerate from seed which survives in the soil for about 15 years. Contractors may be of value in controlling large infestations given sap hazard. Root removal or root cutting In the early spring (April/May) before the leaves are too large, the whole plant can be completely removed by digging the tap root or by cutting the tap root approximately 15cm below ground using a sharp object such as a spade to separate the root from the stem. As long as the upper 15cm of root is removed the plant will not regrow. The site should be checked again in the mid-summer for regrowth and the process repeated. The root sections should be left to dry out in a secure location exposed to direct sunlight for two weeks to ensure the root sections are dead. Once the root sections are dead they can be burnt or left to rot. Avoid taking the roots off site for disposal and do not put in the recycling bin. There are no specific laws preventing a householder from having a bonfire but there are laws for the nuisance they cause. For further information see https://www.gov.uk/garden-bonfires-rules Mowing and cutting Caution – do not cut with The plant can be mowed when it is small and continue to mow throughout the growing a strimmer as it can flick season. Do not mow the plant if it is larger than your mower and never mow if there toxic sap onto skin and is a flower or seed head. Plants must be cut at least three times during the growing clean mowers after use season for several years. Mowing will eventually kill the plants by exhausting the to remove the toxic sap. energy in the tap root. If there is a flower head remove this first (see below). Management Control Options - Continued Flower seed head removal The flower heads can be cut off after the seeds have formed but before they start falling off the head (late August/September). If the plant is small the best method is to bag the head first and cut the stem below. This can be done with a bin liner and aims to stop any seeds from falling. Seed heads should be allowed to dry out as above and burnt or left to rot. This method will not kill the plant but prevent it from seeding. Herbicide control Herbicides can be applied to the plant foliage between late April and early June and again in July or August. Spray is usually directed on to the leaves of the plant and the sites are revisited annually to check for regrowth of old plants or new plants from seed. Triclopyr is the preferred product early in the season as it is selective (does not kill grasses) and has an effect for 6 weeks after application. Glyphosate is also used at a similar timing but it is non-selective so will kill all other vegetation. Both herbicides are taken into the plant via the leaves and stems and moved to the roots (translocated). After treatment After removing invasive non-native species, it is important to re-establish native species of plants. This will help to achieve control, reduce soil erosion and provide competition to prevent further infestation. Selecting a contractor It may be appropriate to employ a specialist contractor for assessing the Lists and details of contractors can be best method of control and to apply any pesticides. Good contractors found through the sites below. will have the following: • A BASIS certified practitioner with knowledge of control of Amenity Assured Compliant Contractors invasive weed control to recommend appropriate chemical More information from control options. BASIS: www.basis-reg.co.uk • A spray operator who holds the appropriate National Proficiency 01335 343945 Tests Council (NPTC) certification for herbicide use or works National Association of under the direct supervision of a certificate holder. Agricultural and Amenity • If sprays are to be applied in or near water, the person carrying Contractors have a list of out or supervising the spraying must have the appropriate contractors in the Amenity aquatic part of the qualification.