Giant hogweed (Heracleum mantegazzianum)
Giant hogweed is a native of the Caucasus mountains and was introduced to Britain in 1893 as anornamental plant. It escaped fromgardens and now colonises manyareas of wasteland and riverbanks throughout the UK. The initial source of induction to the Deveron district was probably at Leith Hall on the Bogie tributary south of Huntly. By the 70’s and 80’s the plant had colonised a majority of the catchment which saw the council adopt an eradication scheme to control the species. By and large a great job was done and with council funds lacking many heavy infestations where cleared allowing native wildlife to flourish once again. As the plants slowly disappeared so did council funding and the eradication scheme until the commencement of the river Deveron Biosecurity Project.
The difficulty with Giant hogweed in the district is that each flower head produces several thousand seeds that are easily dispersed by water, so the plant spreads rapidly along watercourses. So quite literally you only need to miss only plant when treating an area to undo all you good work and effort. Project research has found that there is now a huge seed bank held in suspension of the river Deveron and its tributaries. These seeds can be preserved in clay sediments for many years allowing for untimely river spate occurrences to once again replenish the banks of the river with a fresh supply of seeds ready for germination.
After germinating the plant is a perennial, taking up to four years to mature and flower, after which it dies. People tend to misjudge our native cow parsley as the plant when wondering close by watercourses. There is room for this error as the cow parsley is the Scottish cousin to this foreign invader. Although there can be no mistaking when scale is involved as the giant hogweed has features that are over 300% larger than its native relative. You have probably seen it during summer months when it forms dense colonies that stand tall like regimental soldiers on the sides of fields, streams ditches and river banks. The biosecurity threat posed by the species is that due to its size it suppresses the growth of native plants and grasses, leaving the banks bare of vegetation in winter, increasing the risk of erosion and consequently silting up of valuable spawning grounds for wild salmon and trout.
The project has now completed two years of pesticide spraying assisted by River Champions. All in all within this short time, notable reductions have occurred and it is believed that we may eventually be able to control the spread of the species. If there is more support from local land owners eradication is a possibility.
The project officer would like to hear from any children living locally who have either been burnt by hogweed or maybe it is living close to where they play. The Trust are hoping to cover a piece for BBC Scotland over the coming months to raise awareness to children nationally so more children can be made aware of this troublesome and dangerous plant. If you would like to be considered write to the project officer at my office DBIRCT, The Office, Avochie Stables, Avochie, Huntly, AB54 7YY, please be sure to include photographs.
For further information: Environment Agency, Manley House, Kestrel Way, Sowton, Exeter EX2 7LQ and www.nonnativespecies.orgSee also the RAFTS Invasive Species and Biosecurity Programme website.
