Get to the root of successful weeding
We’ve all seen it: A neglected garden or vacant lot is knee-deep in dry weeds. Then someone cuts them all or hires others to do it. The resulting stubble and bare earth last a few weeks, or until the fall rains begin, and then it all grows back. By the next spring, it’s as though no one had touched the weeds. The person responsible for the land throws up his or her hands in despair: “I have tried, but they just come back.”
Or we see a garden planted with nice plants but ruined by unattractive weeds that stick up through everything. It might be tackled once or twice a year. Again, it always looks just as bad a few weeks later.
You can never get rid of weeds entirely, but you can do so much better than this. Here are a few secrets to weed fighting that will magnify your efforts by many times.
Weed-fighting secrets
The first secret is that you are not fighting weeds, but the seeds and underground structures that reproduce them. It isn’t effective to take weeds out after they have dropped their seeds on the ground, or to chop off weed tops after the plants have made multiple new bulbs or runners underground.
Which leads to the second secret: In our Mediterranean, wet winter climate, the most important time to weed is fall and winter — October through February, when many weeds are still young. Waiting until weather warms, in March, April or later, and weeds have reproduced for the year, is a sure recipe for having as many or more weeds next year. (In a wellmaintained garden, most of the weeding is done before the weeds are big enough to show.)
A third secret is that the most important weed in your garden is the one you haven’t seen there before. Pull or dig it out fast, before it can drop seed or get established underground. When there is only one specimen in a garden, that weed is most vulnerable to elimination. If it has formed a patch, start at the edge of that patch and work to the center to get rid of it.
Finally, it helps to know your weeds. To get rid of a weed that has established itself in your garden, you need to learn to “ungrow” it — the opposite of the plants you want to grow. You only need a few facts about a weed to make yourself an effective weeder.
Weeder’s resources
The main information you need to know is how it reproduces. If by seed, you need to learn when it blooms, what the flower looks like, and when the seed is hard and ripe. Some weeds, for example fennel and wild radish, flower once a year, mostly in spring; but some flower throughout the year. If a weed multiplies by underground structures, you need to know what they look like and when new ones form. For example, yellow oxalis reproduces by bulblets, which multiply over winter. Digging, or even pulling it before March prevents it from multiplying that year.
So how do you identify the specific weeds in your garden and learn the best way to get rid of them? Here are some resources to help:
The University of California Statewide Integrated Pest Management Program sponsors Web resources to help you identify and manage weeds. The overall weed portal (http:// bit.ly/2wTkovY) is where you can find descriptions of many common weeds, including how they reproduce. If you click on “Weed gallery,” you will find a key to identifying weeds, or, if you know the name of the weed, you can find it by name.
(Note that herbicides are listed in some parts of this website, but that the essay on Weed Management in Landscapes includes the sentence: “Generally, home gardeners should not need to apply herbicides to existing landscape plantings.” I agree. Among other reasons, I note that herbicides often leave seeds and underground reproductive structures unharmed and ready to grow.)
The UC Division of Agriculture and Natural Resources (ANR) also publishes “Pests of the Garden and Small Farm: A Grower’s Guide to Using Less Pesticide,” 2nd edition, by Mary Louise Flint. This is an immensely useful book that includes a section on weeds along with other pests and garden problems. (You can buy it at http://bit.ly/2wTS3G5 or by calling (800) 994-8849.)
My book “Golden Gate Gardening,” (Sasquatch Books, third edition, 2010) includes a chapter on weeds with overall help in managing them and individual listings that identify weeds and tell how they reproduce. Available in bookstores and nurseries.