Did anyone else hear the item on Radio 4 this morning about Plantlife’s road verge campaign and associated petition? I listened carefully to the discussion and am broadly supportive of what they are trying to achieve. But I was immediately struck by a comment that local councils should cut the verges “from mid July onwards” because most plants will have set seed by then. I’ve seen this advice given before and whilst it might be an appropriate option for plants, it could severely impact local pollinator populations.
The printed advice that Plantlife is offering (which can be found here) states that if it’s only possible to cut a verge once a year:
“Cut the full width of the verge….between mid July and September. This allows plants to flower and, importantly, gives time for seed to be set.”
This misses a vital point: between mid-July and September there is still an abundance of flower-visiting insects that require these flowers to provide resources for their nesting and egg laying activities, or to build up reserves of energy to allow them to hibernate, particularly newly-mated queen bumblebees.
Where’s the evidence to support my assertion? It’s been demonstrated by a number of studies, but I’ll point you in the direction of a paper that came out of the PhD work of one of my former students, Dr Sam Tarrant, who now works with RSPB. If you look at Figure 4 of this paper, you’ll see that on restored landfill sites the abundance of pollinators in autumn surveys (conducted September-October) was just as high as for summer surveys. On nature reserves, which are routinely cut from mid-July onwards (see Figure 2), this was not the case.
Climate change means that flower-visiting insects are now active in the UK for a much longer period of time than was previously the case, up to at least November in the south of the country. I agree with Plantlife that road verges are important habitats for plants and other wildlife. But advice that suggests cutting floral resources at a key time of the year for these insects is simply misguided. A cut between October and December would be much more appropriate.
I don’t use Twitter so if anyone could point this at Plantlife’s account I’d be interested to see what their reaction is.