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Alien Invaders

posted 12 Sep 2010, 14:01 by Haley Whittall   [ updated 18 Sep 2010, 12:51 ]
Conservation work often requires the removal of invasive species such as Japanese knotweed (Fallopia japonica) and Himalayan balsam (Impatiens grandiflora). These are both non-native species capable of out-competing our native flora and establishing a monoculture that upsets the ecological balance, with a consequent impact on invertebrates and other native wildlife. Anyone using the train from Crowborough in summer may have noticed the extensive stands of pink Himalayan balsam along the banks of the Medway around Eridge.

Not all non-native species are invasive but to protect our natural habitats these two troublesome species need to be controlled. However, they propagate by very different methods so the control measures are also different. Himalayan balsam has explosive seed pods that fling seeds several metres from the parent plant. Therefore it can be controlled to some extent by simply pulling it up, preferably before flowering, although seeds can also be spread long distances by water. Since this plant is often found by water, it can easily reappear at stream habitats such as the Ghyll so Crowborough Conservation will be helping the town council in this battle.
Japanese knotweed on the other hand, spreads by underground rhizomes that extend several metres from the parent plant and run several metres deep. A small piece of rhizome can easily develop into a new plant. Control and disposal of Japanese knotweed, therefore, requires specialist treatment. Unlike Himalayan balsam, you can’t just pull this one up.

More information on some familiar invasive species and their control can be found in this
Environment Agency leaflet
by Pete Meiners