A wonderful plant to get children interested in nature, writes Jillian Macready, is Himalayan balsam (Impatiens glandulifera) as the seed heads explode on touch when they are ready to disperse. However, this makes it a major weed problem, invading gardens and allotments but especially riverbanks and waste ground which don’t attract gardeners dedicated to spotting it before it gets out of hand. Some river catchments have acres and acres of nothing but HB and it is a serious problem for councils, water companies and the Environment Agency.
The plant is pretty and its helmet-shaped pink flowers are much loved by bees but each plant has the ability to produce 800 seeds and when the seed head explodes, its load is carried downstream in the water to infect other parts of the river.
It is also a fast growing annual, quickly getting to 10 ft in the right conditions and tolerant of shade and difficult areas so it can grow anywhere, shading out the natural vegetation. They and other non-native invasive plants displace native species and detrimentally affect the ecology of many vulnerable habitats. Its huge hollow stems and fleshy leaves are mostly water, so in the winter it dies down to nothing, leaving bare river banks which are then able to wash into the river with the first heavy rain.
This isn’t the only plant the Victorians brought to Britain as they were avid plant collectors from all round the world, but they had no idea of the damage some of these plant would wreak. Some £2bn of tax payers’ money is spent each year reducing some of the non-native invasive species which have naturalised here. HB is relatively easy to remove as it can be pulled easily with bare hands but others such as Giant Hogweed (pictured) can cause serious skin irritations, rash and sensitivity to sunlight if touched and Japanese knotweed is virtually impossible to irradiate with weed killer. Luckily Japanese Knotweed has not been reported in Bury St Edmunds but it is in parts of East Anglia.
We do have some Giant Hogweed (Heracleum mantegazzianum) in the River Linnet in Bury St Edmunds but the council is aware of it and has a programme of irradiation. It’s worth familiarising yourself with it so that you don’t touch it by mistake as it can be mistaken for the harmless and very beneficial native Hogweed or cow parsley to which it is related and which must not be removed. It has thick bristly stems that are often blotched purple unlike hogweed or cow parsley and is twice the size once it flowers. It’s biennial so has a rosette of jagged lobed leaves in the first year and then sends up an enormous hogweed-like flower spike of white flowers the following year.
The EA and other bodies have joined forces to help combat the spread of the UK’s most problematic invasive non-native plant species by coming up with Plant tracker. The first step in tackling this problem is accurately determining where the plants might be and they need our help with this. Plant tracker is also an App for Iphones and Androids so you can notify the Agency while you are out walking.
Speak to us if you don’t know how to use the website or App or report it to us if you see Giant Hogweed or Japanese Knotweed. A successful “Balsam bashing” work party was carried out recently, with another on Sunday 23rd July in the areas of the Linnet which we didn’t manage to check. If you want to join us next time, please get in contact here. Also, don’t forget the workshop coming up later in August.