Weeds, in gardens or in nature, are subtle invaders. Like miniature terrorists, they blend in for a while, hardly noticed and appear to assimilate with their neighbors. But eventually, if not rooted out, bad things begin to happen.
In natural areas weeds contribute to desertification, drought, global warming and displacement of our native plants. Weeds encourage pest animals like Starlings, mice, rabbits, rodents and introduced insects. Weeds contribute to Lyme disease and the siltation Upper Newport Bay and other waterways. On local hillsides weeds increase the fire frequency from once a century to once a decade.
Weed invasions create alternate systems that do not support natural, native processes. In turn, a nearly sterile ecosystem favors more weeds. Soon, a diverse healthy native habitat is destroyed, replaced by something that is green, but otherwise nearly lifeless.
Weeds are subtle in their assault; hardly noticed, until the consequence of their presence is beyond repair. Even then, because weeds are stealth invaders, they are seldom held accountable for their actions. There is nothing good about weeds.
In a garden, many traditional activities may favor weeds. Disturbing the soil by tilling and cultivating favors weeds. Fertilizer favors weeds. Watering favors weeds. Soil compaction favors weeds.
With last month’s winter rains, weeds are sprouting everywhere. Glance out the window to your garden, notice the vacant fields as you drive along and gaze toward our nearby canyons and hillsides. Those aren’t wildflowers and native plants you are seeing. Those little green monsters sprouting underfoot are alien invaders, weeds from distant parts of the world.
There are three strategies for dealing with weeds in a garden; mechanical control, chemical control and cultural control. Usually some combination of all three produces the best results.
Cultivating favors weeds, but slicing off the weed with a shallow hoe or removing it whole with a trowel can be effective. Remove any weed you slice or dig if flowers or seeds are present. Mowers and string trimmers do not control weeds and may assist in spreading the problem.
Weed killers kill weeds. Those that stop weeds from germinating are called preemergents. Others are postemergents and are applied to growing weeds. Weed killers can also be divided between selective types, which are only kill certain groups of plants and non-selective types, which kill everything. When using weed killers timing and proper use is important. Follow the label carefully, especially the details about dilution rates, temperatures and environmental warnings and use only what you need. The most popular method of controlling weeds is to douse them with a synthetic weed killer, like RoundUp. We’re a society of instant results and a bottle of Roundup often is our first impulse. But I prefer more natural methods of weed control whenever I can.
Homemade organic concoctions can work well on young annual weeds, but will not be effective on tough perennial weeds. A blast of vinegar, full strength, sprayed from a plastic spray bottle will work well as well as RoundUp. So will rubbing alcohol, diluted with as much as ten parts water. When using alcohol or vinegar the results can be even better by adding a few drops of dishwashing soap to the mix. Alternatively, a strong dose of plain dishwashing soap, diluted to about five tablespoons per quart of water will also do the trick. Topical sprays, like these, work best on warm sunny days, not cool, cloudy days.
Nature will fill a vacuum. Bare ground encourages weeds. Culturally, a surface mulch, used throughout the exposed areas of a garden will discourage weeds. Apply mulch liberally and frequently; it’s good for the soil, good for the plants, and very good at reducing weeds.
Water the garden only when you need to. Weeds need moist ground to germinate, that’s why they are so abundant at this time of the year. If you over irrigate and irrigate the unplanted areas of your garden your weed problem will be far worse. During our dry summer months there are very few weeds grow in our native canyons and hillsides. No water, no weeds.
Weeds are subtle, evil invaders, causing havoc wherever they appear. But, like terrorists, they can be controlled.
Questions from Readers January 24.
Melody, Huntington Beach
I don’t like to see women cry, so let me help you. Foremost, tomatoes growing during the winter are going to be a struggle, and in my opinion definitely not worth the effort. Yes, tomatoes will “survive” in the winter, but powdery mildew will be a problem you will likely never escape. You’re working against the nature of a tomato plant, not with it. Second, in your location especially, your plants need lots of full all day sunlight and especially good air circulation. Crowded spaces, with walls behind them or in enclosed gardens are going to encourage more mildew. Grow powdery mildew sensitive plants during their natural season, in 100% full sun and with great air circulation and you won’t need that box of tissues any longer.
Ron Vanderhoff is the Nursery Manager at Roger’s Gardens , Corona del Mar.