Know weeds to kill weeds

May 16, 2009|By JEFF RUGG / Creators Syndicate

Q: I already have weeds growing in my vegetable garden and flowerbeds. I am not fond of working at weed control, but I don't want them to take over either. What is the easiest way to prevent weeds from growing or to kill them after they are growing?

A: There are several weed control methods. I will list some and you can decide which is easiest for you.

Weeds can be annuals or perennials. They can be grasses, plants that look like grasses - such as sedges or rushes - or broad leafed.

Annuals of all kinds come back from seeds each year and the mature plant dies each year. If you can prevent the seeds from growing, you don't get a plant that produces more seeds. Every year that you stop the weeds from producing more seeds gets you closer to having a nearly weed-free garden. Crabgrass is probably the most infamous annual weed.


Biennial plants sprout from seeds and produce leaves and roots the first year. At the beginning of the second year, they send out flowers, produce seeds and then the mature plant dies. Thistles are often biennials.

Perennials have roots, stems, bulbs or other parts that survive the winter. Many perennials also produce plenty of seeds to give you lots more plants. Dandelions and many others are perennials.

There are weed control products in granular and liquid forms that are called pre-emergents. They form a chemical barrier on the ground that kills the sprout as it emerges from the seed. If the chemical is applied evenly and at the proper time, it does a good job at stopping annual, biennial and perennial seeds from growing into plants. If the soil is raked or somehow scratched up, the chemical barrier is broken and seeds can come up in that area. The product will last a couple of months and may need to be applied in the fall to prevent some weeds from sprouting at that time of year. Pre-emergents don't kill existing annuals, biennials or perennials.

Once the seeds have sprouted, they become harder to kill. Chemical controls that are designed for killing grass won't have an effect on broad-leafed plants and may not have an effect on sedges. The opposite is also true, as the broad-leafed weed killers won't harm the grasses. Properly applied, most weed killers will do the job they are supposed to do.

If you prevent annuals and biennials from producing seeds, they will die on their own. On the other hand, the longer a perennial has been around, the larger its roots and other storage parts will be. Killing the top part of the roots is helpful, but the rest of the roots will send out new growth that will then need to be killed. A few hard-to-control weeds may need more than one application to finish killing the whole root.

Identify your weeds accurately, chose the control that says it works on that weed and apply it correctly. Don't apply it when the weather conditions could cause it to drift onto other plants. Don't mix more than necessary and if there is any left over, apply it to new areas. Don't dump it out on the ground or into a sewer.

If there are only a few weeds, hand pulling will work very well and requires no chemicals, except maybe some lemonade. A hoe will work, too, as long as you are careful to not to damage the roots of your good plants. The earlier you pull or hoe a weed, the easier it will be and the more likely you are to get the whole root to kill it completely. Make it a weekly habit to check for and pull any weeds you see. This will get most weeds when they are less than a week old.

For the existing flowerbeds, you can add more mulch. A two- to three-inch layer is all that is necessary to stop most weed seeds from sprouting. It is easiest to apply the mulch when the other good plants are dormant and you can move around the bed easily. Mulch in the vegetable garden should be applied when the plants are up and growing. Mulch helps prevent water from evaporating from the soil, making watering more effective. Mulches made from plant materials decay and improve the soil, so they eventually need to be replaced.

A very effective way of stopping seeds from growing into plants and for killing some small perennials is a weed barrier cloth. This fabric lies on the soil and stops weeds from coming up. You plant into it by cutting an X shape and folding the flaps back. Large plants can get a slit cut in from one edge. The material works much better than plastic because it allows water and air to go directly into the soil. Plastic makes the water run off or puddle at the low spots, making it very hard to water plants properly.

The weed barrier fabric often has a 10-to-15-year warranty, if it is covered with mulch. The problem is that the mulch decays on top of the fabric and becomes a thin layer of soil that weeds will easily sprout in. The weeds are easy to pull out because they don't get many roots into the underlying soil. Perennials that you do want to spread will be blocked by the barrier until you cut it away from the spreading plant. The fabric will need to be replaced, but it will have saved a lot of labor for many years.

I highly recommend weed barrier cloth in vegetable gardens. It also keeps fruit off the soil so it helps prevent rotting of many fruits, from tomatoes to cucumbers, cantaloupe and pumpkins.

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