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Responsible Weed Control
by Liesbeth Leatherbarrow
by Liesbeth Leatherbarrow

Liesbeth has written for several western gardening publications, including Gardens West and The Gardener for the Prairies. She has also co-authored three gardening books: The Calgary Gardener (with the Calgary Horticultural Society), The Calgary Gardener, Volume Two: Beyond the Basics (with Lesley Reynolds), and 101 Best Plants for the Prairies (with Lesley Reynolds).

February 22, 2004

It's ironic, isn't it? The plants that most readily, cheerily, and capably clothe bare ground are also those that are most reviled by the home gardener. No matter how you describe them - plants whose virtues have yet to be discovered, plants growing where you don't want them to, or plants of no value and usually of rank growth - weeds are the cause of many a gardener's woes. It needn't be so. Average gardeners can greatly reduce the amount of time devoted to weed control by practising a few simple, sound cultural techniques and exercising a minimum level of tolerance to their presence. After all, weeds are not without their virtues. They provide a home for beneficial insects; attract bees and butterflies; prevent soil erosion on otherwise bare ground; give an indication of a soil's health; and are often tasty and nutritious additions to the family salad bowl. Some are even coveted for their beauty and are frequently grown in ornamental and wildflower gardens. Think of asters, blanket flower, black-eyed Susans, and Queen Anne's lace. It is really true that one person's weed is often another's botanical treasure.
Here are a few ideas on how to prevent weeds from gaining a foothold in your gardens and what to do with the tenacious ones that will manage to penetrate your defenses every time.
Most importantly, do not leave any garden soil exposed; bare ground in flower beds and vegetable gardens is an open invitation for weed fests. At the very least, cover exposed ground with a thick layer of organic mulch while deciding on planting schemes or waiting for catalogue orders to arrive in the spring. Organic mulches have the added benefit of providing nutrition to the soil and encouraging moisture retention, a bonus in our dry climate.
If you prefer the look of freshly turned earth in your garden by all means, cultivate. However, restrict your efforts to the top few inches of soil, barely scratching the surface. This will allow you to easily uproot young seedlings without running the risk of bringing buried weed seeds to the surface where they will, of course, flourish. Maintaining a healthy garden and planting densely in cultivated beds will also help prevent the arrival and spread of weeds by shading the ground and crowding out the competition.
Despite taking reasonable precautions, gardeners will occasionally find themselves face-to-face with the enemy. What to do? For annual and biennial weeds invading small spaces, hand-pulling works well, especially if the soil is slightly damp when you do it. The spread of these weeds can be prevented by pulling them before they set seed. Weeds that re-root easily and those that are already in flower should not be left lying on the ground. Instead, collect them in a bucket for disposal; weeds can still set and disperse seed, even after they have been pulled.
Pulling is not an effective remedy for perennial weeds that reproduce by rhizomes, tubers, and bulbs. These are usually deep-seated and must be dug up. Dig deeply and make sure you get the whole underground portion of the plant to prevent new plants from forming. The repeated application of boiling water to perennial weeds will also kill them. This technique does not yield instant results but when applied with the patience required, is extremely effective.
For weed control of large areas use a hand-held hoe or a rotary tiller, but use the latter with caution, especially on perennial weeds such as quack grass or Canada thistle which have spreading, underground root systems. Chopping up perennial weed roots with a rotary tiller is a recipe for disaster; each small section of chopped-up root can and will develop into a vigorous new plant. If you can leave an area unplanted for a season, repeated rototilling at 10-day intervals may weaken weed root systems sufficiently to stop them from sprouting.
The heat of the sun can also be used to rid large areas of annual, biennial and some perennial weeds. Called solarization, this technique consists of covering bare, moist soil in a full-sun location with clear plastic (at least 2 mils thick), sealing the perimeter by burying the plastic's edge with soil, and letting the sun bake it during part or all of the summer. Early- to mid-summer is the best time to implement such a plan. It is important to rid the targeted plot of soil of all visible weeds through hand-pulling before applying the plastic cover. The process takes anywhere from six to twelve weeks to complete, depending on the ambient air temperature; the higher the temperature, the quicker the fix. Regretfully, solarization also kills the beneficial soil organisms that facilitate the absorption of plant nutrients. However, the supply of these organisms can be replenished by the simple application of a compost mulch once the treated bed has been planted.

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