Chemical Free Weed Control

Mark Cullen roots a few weeds out of his garden with a hoe.

by Mark and Ben Cullen

Sometimes you can have it both ways.

You can have a weed-free garden without the use of herbicides.   

First, chemical-free weed control is possible if you relax your standards somewhat.

Secondly, there are tactics to a relatively weed free and chemical-free garden.  Here are our favourites:

  1. Crop rotations minimize weed pressure in the veggie garden before it even happens. If you have been growing tomatoes on the same patch of bare soil for many years, a bank of weed seeds will have accumulated over time which can compete easily with your tomatoes. Try sowing a cover crop in that section, such as an alfalfa or clover mix, which will out compete the weeds for a season while building up the soil again by fixing nitrogen out of the atmosphere.
  2. Competition. Plant higher densities of the plants you want, and it will be harder for weeds to take over.
  3. Mulch. Proven to reduce weed pressure by up to 90% and reduce watering by up to 70%. Mark prefers 2 to 3 inches of shredded bark mulch whereas Ben prefers straw, whatever your preference it will minimize weeds.
  4. Solarizing. Where you have a stubborn patch of weeds, like twitch grass or Canada thistle, you can literally bake them out of existence. This takes patience. The trick is having full sunlight, as you are harnessing the suns rays to burn them off. Use a sheet of clear greenhouse plastic at least 3 mm thick and secure it down over the area for 8 to 12 weeks during the hottest part of the summer – July is a great time for the job. Temperatures can exceed 49oC which will also wipe out soil-borne diseases and pests.
  5. Burning weeds, it is easy to overkill. Weed torches have been around a long time and many people have had mixed success – often because they want to scorch the plants to the ground. Not necessary. Simply pass over the green weeds slowly, enough to burst the leaf cell walls. They will wilt in a few days. Repeat this process a few times until the plant has run out of energy. Tip: Mark uses a two wheeled cart to mount the propane cylinder on.
  6. Electronic weed zappers follow a similar premise to the propane-powered weed torches but run on a high-voltage electric current, where an electronic wick drives a current through the plant, bursting cell walls. While the consumer-friendly zappers we have seen look sketchy to outright dangerous, this is a somewhat common practice in organic farming where implements can run off the power of a tractor. As one of Cullen’s Foods organic bean growers put it, “smells like a vegan barbeque!”. Delicious.
  7. Chemical-free herbicides such as horticultural vinegar (contains acetic acid) can show some immediate effect but in our experience are not effective long-term and requires regular re-application. As these things go, “the dose is the poison” and it begs the question- is such a high volume of vinegar good for your soil? We do not have a scientifically proven answer, but we would rather not have it.
  8. Hoeing – you have one in their tool shed but avoid using it. Here is the rub: the earlier you remove weeds with a sharp hoe, the less work you will have pulling them later. The secret to successful weeding is to sharpen your hoe and use it while weeds are young. This time of year, the weed seedlings that are sprouting in your garden will die when you cut them down and leave them exposed to the sun to bake for a few hours.

Repeat the treatment every two or three weeks to keep weeds under control and you will never have to hurt your back yanking on a deeply rooted burdock again. 

Fact is, many gardeners have learned to enjoy the quiet contemplation that is part of the weeding experience which is why early in the morning or late in the evening when the birds are singing is the best time to weed with a hoe – and appreciate your garden, imperfections in all.

Mark Cullen is an expert gardener, author, broadcaster, tree advocate and Member of the Order of Canada. His son Ben is a fourth-generation urban gardener and graduate of University of Guelph and Dalhousie University in Halifax. Follow them at, @markcullengardening, and on Facebook.