Weeds come in all types—large or small, prickly or smooth, native or introduced, some with pretty flowers and others with blooms so insignificant you never even notice them. They can drive us crazy but there are ways to shut them out.
Weeds pop up in the places where you least want to see them: on our lawns, in our gardens, or between patio stones and pavers in our driveways. Wherever there is the slightest crevice or hole, up they come. And they do damage, too. Weeds can smother garden plants, steal their light, water and minerals,
and eventually, take their place. That’s reason enough to want to eliminate them! But when they poison our pets or leave us and our children suffering from skin irritations and allergies—as some of them do—removing them from our yards is a priority.
There are many ways to suppress weeds, but prevention is always the best solution. The most effective method of preventing weeds from infiltrating your garden is to start with fresh store-bought soil that is free from leafy intruders. After planting in the weed-free earth, cover the soil with about 5 to 7.5 centimetres of mulch, such as chopped fall leaves, ramial chipped wood or straw. Mulch prevents light from reaching seeds that fall to the ground, so they can’t germinate. You will need to top up the mulch from time to time since it decomposes over the years; some mulches break down more quickly than others. When the mulch starts to thin out, the sun’s rays can get through, which allows weed seeds to germinate again.
It’s good practice to make sure that the soil you buy doesn’t contain any rhizomes or roots of creeping weeds. If in doubt, deposit a shovelful or two on a flat surface, water it and keep it moist. If new plants emerge from small buried sections of root or stem, the soil is contaminated and you should avoid using it.
You can also try to beat the weeds at their own game. Rather than leaving the space between two taller plants exposed to the air—always an open invitation to weeds—plant a ground cover plant there and let it fill in. It will create a dense carpet that leaves no room for other green visitors. That’s why ground covers are often called “living mulch.”
When the soil is carpeted with a dense ground cover (here, sweet woodruff), there’s no place for weeds to grow.
Among older generations, a popular method for eliminating weeds in the garden was cultivation using a hoe, cultivator or other long-handled soil tools. Gardeners would spend hours turning the soil between rows of their favourite vegetables and flowers, pulling out, digging up and slicing unwanted plants. Cultivation kills the weeds temporarily, but they grow back quickly (and more densely!). That’s because cultivating breaks rhizomes into small pieces and each piece soon produces a new plant. It also brings dormant weed seeds to the surface, which can then germinate and start a new invasion.
To make matters worse, we now know that cultivating the soil destroys its structure, rendering it hard, compact and not favourable for good growth. For these reasons, cultivation is no longer commonly used as a weeding technique. If you choose to use this method, remember that you’ll need to repeat it once every 10 to 14 days.
Actually pulling weeds can be more effective, especially those like dandelions and plantain that lack creeping rhizomes. Make sure to water 24 hours beforehand, which makes the roots slip out of the soil much more readily. A dandelion weeder can be useful in this task. It looks like a screwdriver with a forked tip. Simply press the fork against the base of the plant, then grab the leaves and pull up slowly but firmly with one hand and while pressing down on the handle of the tool with the other, like a lever. The plant pops out of the ground like magic! Don’t forget to cover the hole left behind with mulch; otherwise, a new weed will sprout there!
It is also possible to kill weeds with creeping roots by covering the entire area with a black tarp or a piece of old carpet for one year. Without light, they’ll exhaust themselves and die. Sometimes it even takes a second year to eliminate very persistent weeds like horsetail.
These days, the most commonly available herbicides or weed killers are non-selective ones. The idea is to spray them only on the plant to be eliminated because they’ll also kill neighbouring plants if they reach them. Read the label carefully and follow it to the letter. If you’re leery of chemical weed killers, you’ll discover that many nonselective herbicides are organic, usually made from vinegar or citric acid.
You can also make your own non-selective weed killer out of vinegar. However, ordinary white vinegar and other cooking vinegars have weak concentrations, containing only five to seven percent acetic acid, and are unlikely to be able to kill anything other than young leaves. Horticultural vinegar (with 10 percent or, even better, 20 percent acetic acid) is much more effective. A little liquid soap is usually added to it so that the vinegar will stick to the leaves. Horticultural vinegar will kill even tough older leaves and sometimes roots as well.
Many homemade recipes you can find on the internet suggest mixing salt into white vinegar, but then any ecological pretensions fly out the window. Salt
is not an ecologically safe product to use in your garden because it kills weeds by making the soil toxic. There is also a serious risk that salt-based herbicides will poison the water table and nearby waterways. Plus, soil contaminated with salt can remain toxic for decades. Not very environmentally friendly, is it?
Controlling weeds on a lawn is particularly tricky. When a lawn is taken over by plantain, dandelions or some other weeds, how can you keep the sod alive and healthy while eliminating the unwanted plants? Here are a few tips:
- Hand-pull the weeds. It’s important to fill the hole left behind with topsoil and drop grass seed onto the soil, otherwise weed seeds will soon settle in the empty space.
- Spray a nonselective herbicide directly onto the plant to be eliminated, being careful not to damage the surrounding grasses.
- Apply a pre-emergent herbicide. This treatment will only be effective against weeds that grow from seed, such as crabgrass, and has to be applied just before they germinate.
- Hire a lawn care company to do the job with whatever selective herbicide they are legally allowed to use.
Here are 10 of the most common weeds found in our lawns and gardens:
Canada thistle (Cirsium arvense)
A large perennial plant with spiny leaves, pinkish-purple flowers and feathery white seed heads. It spreads via invasive rhizomes and is found in lawns and gardens.
Crabgrass (Digitaria sanguinalis)
A low-lying annual grass with fairly wide pointed leaves in a yellowish hue with slender green flower spikes. Mostly found in lawns and along roadsides.
Dandelion (Taraxacum officinale)
Easily recognizable, this plant has a low rosette of toothed leaves and double yellow flowers that bloom in May. Found in lawns, gardens and along roadsides.
Ground ivy (Glechoma hederacea)
This creeping perennial plant has small heart-shaped leaves and pretty purple flowers. It spreads via invasive runners. Found in lawns and gardens.
Horsetail (Equisetum arvense)
A perennial plant with no true leaves, the narrow green stems form an open ponytail. Fertile stems emerge in early spring and lack chlorophyll. Found in gardens and lawns.
Lamb’s quarters (Chenopodium album)
This annual, fast-growing plant has mealy looking upper leaves and spikes of whitish-green flowers on top. Found in gardens.
Plantain (Plantago major)
A low-lying perennial plant with a rosette of leathery spoon-shaped leaves with parallel veins and erect spikes of insignificant flowers. Found in lawns, gardens and roadsides.
Ragweed (Ambrosia artemisiifolia)
An erect, annual plant of variable height with deeply cut yellowish-green opposite leaves. Narrow spikes of green flowers bloom in late summer. This plant is a major cause of hay fever. Found in lawns and along roadsides.
White clover (Trifolium repens)
No longer considered a lawn weed by many gardeners, this perennial plant is identified by rosettes of trifoliate leaves and small, whitish globular flowers. It spreads via creeping runners. Found in lawns and gardens.
Woodsorrel (Oxalis stricta)
This small upright annual plant has trifoliate leaves and yellow flowers with five petals. It spreads via creeping runners. Found in gardens.