bees, honey and other sticky subjects

Tuesday, October 12, 2004

Bees aiding and abetting policeman's helmet

I've often heard claims from beekeepers that honeybees are always good for the environment. Well, it's not always that simple:

I've noticed that a lot of Czech interest in my blog on gorse in New Zealand. It transpires that they have a problem, not with gorse, but with another weed that is attractive to, and pollinated by, bees: Impatiens glandulifera (known in the UK as Indian or Himalayan Balsam) (picture).

In the Czech Republic, it seems problems can arise along banks of rivers: Impatiens glandulifera overhelms other plants on river banks, but after the early autumn frosts the banks are left nearly bare and are more easily eroded. Here's how Czech volunteers try to fight it. The photos are from Prateleprirody (Friends of Nature), a nonprofit organisation focusing on nature preservation on Labe (Elbe) river.

In Northern Ireland, where the balsam is called “Policeman's Helmet”, it has also flourished. On the Flora of Northern Ireland website, a related problem is explained:
The plant has similarly colonized many rivers on the European continent and recent research by two German botanists has shown that it competes for pollinators such as bumblebees with the native riverbank species, and so reduces seed set in these other plants. Its success in this is in part due to a very high rate of sugar (nectar) production -- for instance about 47 times greater than the great willowherb (Epilobium hirsutum) and about 23 times greater than purple loosestrife (Lythrum salicaria). Seed set in marsh woundwort (Stachys palustris) is reduced by some 25% where it grows mixed with Himalayan balsam plants as compared to pure patches.


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