The Himalayan balsam flower trembles: a bumblebee is struggling to escape its floral chamber. As it stumbles out through a portal barely broad enough to accommodate its rotund body, the furry visitor is smeared with white pollen, forcing it to clean its eyes before plunging into the next bloom: another successful pollination.
There has been a dearth of bees this summer, but these balsams are humming with honeybees and bumblebees, addicted to the rich nectar flow that Impatiens glandulifera delivers, five times greater than native wildflowers. They’re also a rich food source for far longer than our native flora, still producing flowers until the first frosts.
The bees love it, though some people detest its tall, visually assertive Barbie doll-pink blossom, at odds with a vision of shady, verdant margins of an English river in summer. I once heard it described as “like adding a flock of flamingos to the banks of the Stour millpond in The Hay Wain”. Invasive species pay no heed to cultural sensitivities.
A few days ago, downstream along the River Wear, we found a decaying heap of the same plants, uprooted by “balsam bashers” fighting its tendency to suppress native riverbank flora. A valiant but Sisyphean task, likely rendered futile by the pollinating bees we’re watching today, guaranteeing another heavy seed crop upstream, soon to be scattered and deposited by winter floodwater on to a fresh seedbed of bare, effluent-enriched silt.
The edge of this balsam thicket is interlaced with sky blue flowers of native meadow crane’s-bill that offers relatively meagre nectar rewards, so the bees seem to be ignoring it. Two plant species that evolved in isolation on separate continents, now competing for the same resource – a reminder that this is an era of no-analogue plant communities, of mingling species that, until humans intervened, never coexisted in the same place but which are now adapting, winning and losing, during a period of rapid climate change. Viewed from a dispassionate scientific perspective, a fascinating accidental evolutionary experiment.
Balsam may be monopolising the bees’ attention, but there are other players involved. Some of its leaves are scarred with reddish-brown fungal lesions, many show greyish-translucent patches, mined by fly larvae. Maybe Himalayan balsam, approximately 170 years after escaping from Kew Gardens into the wild, is acquiring its own burden of opportunists that will eventually slow its spread.
• Country diary is on Twitter at @gdncountrydiary
• Under the Changing Skies: The Best of the Guardian’s Country Diary, 2018-2024 (Guardian Faber) is published on 26 September; pre-order now at the guardianbookshop.com and get a 20% discount
