Sometimes our use of weedkillers is like being hooked on oil – it’s just so hard to go the long way round and find a more environmentally friendly alternative. So, a bit like our use of oil, I have been thinking about ways in which we can make weedkillers effective while minimising their impact on everything else including our food chain.
Roundup is probably the weedkiller that we use most widely, and it is very effective. It’s at its most effective on really troublesome weeds like docks and thistles and bindweed and nettles and willowherb when those weeds are in flower. But that is the time when bees most frequent those weeds and bees can ingest the Roundup from contact with the flowers. Roundup residues, and mites and climate change effects are all calculated to contribute to reduced bee numbers. It is possible that bees in turn could pass Roundup residues up along the food chain in pollinating other food crops.
For the thinking home gardener struggling to control difficult weeds, one way is to bruise the weeds then spray Roundup, and to do this before the weeds come into flower. In this way the bees will not come into contact with the sprayed Roundup. Bruising the weeds means going over them with a light roller, walking on the weeds, beating them with a stick, or in the case of bindweed, pulling the flowers off before spraying. Bruising the weeds, just before they flower, allows the Roundup weedkiller to enter fully into the weed and to kill it ahead of when you would normally expect to get the best kill. It enables you to kill off troublesome weeds while reducing significantly the risk to bees – and other pollinating insects.
There is a final twist to this story: the best time to kill brambles with Roundup is not when they flower. It is when the flowers and fruits have gone and while the leaves are still a healthy green. This is usually in late September to mid October. I have found that the safest thing is to wait until the birds have eaten the fruits then spray the leaves. In this way you are protecting both bees and birds!
The attached photo is of rosebay willow herb ( willow herb) the flowers of which are much loved by bees.
Mike McKenna writes his blog from Blackwater Garden Centre, part of the Waterford Garden Trail.