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Passion For Plants

Whittling Down Those Wily Weeds


The best way to get rid of weeds is to know your enemy.

Happy New Year, everyone! For my first column of 2017, we need to talk about weeds. One of my perennial resolutions is to get a handle on my weeds. I think most anyone with a garden, or even someone who only gardens in containers, knows the frustration that can come with a healthy crop of weeds. After all, weeds are such wily opponents.

Have you ever noticed that weeds always seem to grow in the company of plants they resemble? And that they do this as soon as you turn your back? Maybe I’m just imagining it, but let’s look at some real-world solutions for weed control.

One of the first steps to take in the war against weeds should be prevention. If you can keep weed seeds from germinating in the first place, you’re ahead of the game. Four to six inches of mulch, especially with a layer of cardboard or sheets of newspaper underneath, can effectively keep sunshine away from the weed seeds. Without sun the seeds aren’t able to sprout and grow. If you’re a lazy but patient gardener, look into sheet composting. This technique suppresses weeds and has the added benefit of improving your soil at the same time. Plastic-type weed barriers can be used, but they’re unsightly when exposed. Solarization is a method of killing weed seeds by harnessing the sun, but it requires you to leave an area fallow for a month or two. In addition, there are also both chemical and organic pre-emergents. These substances are spread over an area before seed germination begins and prevent germination. Corn gluten meal is an organic pre-emergent. I’ve had mixed results from my trials, and my experience is reflected in a UC Davis Weed Science publication, but a friend has been pleased with her use of corn gluten meal.

Suppose you spent your time visiting nurseries or teaching a child how to plant an acorn, and the weeds in your garden sprouted when you weren’t watching. What do you do? Well, it really helps to learn about your opponent. There are both annual and perennial weeds. If you can recognize weeds at the seedling stage, both types become much easier to eliminate. Small weeds can be pulled, hoed or hit with a weed torch and burned. When you pull weeds, be sure to get as much of the root as you can, because some weeds can re-grow from small pieces of root left behind. Small weeds can also be sprayed with a variety of organic sprays—remember to use with care and wear protective clothing. Also be aware that home-made sprays from vinegar, salt and dish soap should never be used where you want plants to grow in the future. Accumulated salts are deadly to all plants.

As far as I know, all organic sprays are contact killers and not effective controls for perennial weeds. If you want to use a spray to control well-established perennial weeds—such as poison oak, mustard or dandelion—only a conventional herbicide (e.g. glyphosate) will translocate into the roots for effective control. When it comes to weeds, it’s a never-ending battle. Even annual weeds are a perennial problem.

~ Nancy Schramm is the third generation owner of Carman’s Nursery. She and her husband have lived in Gilroy for more than 30 years. Contact her at 408.847.2313 or visit www.carmansnursery.com