Ecological Weeding

A parasitised aphid (the bloated brown one), and an unparasitised one (the green)

A parasitised aphid (the bloated brown one), and an unparasitised one (the green)

As much as I enjoy weeding, I can’t possibly keep up with them all. There are always weeds on the property.

In truth, I don’t try to eliminate all the weeds. I take a ‘live and let live’ approach with many of them. I also recognise the utility of many of the weeds on the property–or at least their utility to other organisms.

Except in the vegetable garden where they are, literally, a pain, I allow nettles to reside in the yard. They provide food for our native yellow admiral butterflies and, in a pinch, can be used to make rennet for cheese making. Even in the vegetable garden, I don’t mind seeing them–they hate dry soil, so they’re a good indicator that I’m watering the garden enough for the vegetables.

Weeds like yarrow, clover, and dandelions are good food sources for beneficial insects, so they, too, are allowed to grow wherever they’re not in direct competition with crops.

Weeds are also sometimes good ‘trap crops’, attracting pests to plants (themselves) I don’t mind pulling out and destroying to get rid of the pest.

Sometimes, though, the ‘trap crop’ idea backfires on me. Today I noticed that a sow thistle I’d allowed to grow was covered in aphids–it was a great opportunity to destroy thousands of pests. Except that as I bent to pull the weed, I noticed that a large number of the aphids were parasitised by wasps. I depend upon these wasps to deal with my springtime aphid problems. Short of painstakingly picking off every parasitised aphid and caring for them until the wasps hatch, killing the aphids on the weed is going to kill the wasps, too. What to do?

So the weed has gotten a temporary stay of execution. I’ll keep an eye on it. When the wasps have emerged from the parasitised aphids, I’ll pull it and kill the remaining aphids.