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The Homeowners Column
Control Options for Weeds
Extension Educator, Horticulture
One handy thing about a good soaking rain is that weeds pull out easier. Of course one person's weed may be another person's wildflower. My weeds tend to be garden plants gone wild. Whatever your definition, weed is a four letter word to gardeners.
As garden author Roger Swain says "there are no pacifist gardeners". Once you decide to grow anything, whether it's for food or beauty, you will at one time or another find yourself in hand-to-hand combat with weeds. The battleground is usually bare soil. Dig a new garden bed and all those dormant weed seeds shoot up.
By mid summer, weeds may be waist high. Weeds have a few things in common. They grow rapidly, flower quickly and produce vast quantities of seeds. Supposedly one good size lambsquarter can produce 70,000 seeds. Weeds compete with our garden plants for light, nutrients and water.
Once you have decided a plant is a weed, here are some weed control options.
First identify the weed. Is it an annual, biennial or a perennial? Annuals live one growing season and must come back each year from seed such as crabgrass, foxtail, goosegrass, lambsquarter and buttonweed. Biennials live two years producing the seed in the second year such as burdock and poison hemlock. With perennials the same plant comes back each year such as dandelions, creeping charlie, and quackgrass.
Whatever you do, do not let weeds go to seed. Remove or mow off the tops before seed is produced. "One year of seeding equals seven years of weeding".
Hoe, till or hand pull – These methods only control existing weeds, therefore they must be continued throughout the season. Hoe and till shallowly so as not to damage the roots of desirable plants and bring more weeds seeds to the surface. Perennial weeds will require frequent recutting until the food reserves are depleted.
Mulch - Mulching controls weeds by preventing light from reaching the weed seeds or seedlings. This method is best for controlling annual weeds. Mulching also conserves moisture, prevents soil crusting, reduces erosion and keeps above ground food crops clean. Organic mulches include wood chips, straw, dry grass clippings and even newspapers. Synthetic mulches such as black polyethylene can be used in vegetable gardens. However they must be picked up every fall and have to be disposed of after a couple of years.
Plant cover crops in the garden - Repeated plantings of buckwheat will help to deplete the weed seed bank. Winter rye can keep weeds from taking over bare soil areas and when tilled in the spring can also enrich the soil.
Plant something... anything, ground covers, grass etc. - Bare areas will invite weeds. Scalp the lawn and weeds will germinate before the lawn mower sees the garage.
Herbicides – The most common in home gardens are DCPA sold as dacthal and trifluralin sold as Treflan or Preen. Both of these are preemergent herbicides which mean they keep the seed from emerging through the soil. Therefore they do not control existing weeds. Also these herbicides work best against annual grasses.
Perennial weeds can be controlled by nonselective herbicides such as glyphosate sold as Round up or Kleenup. It must be applied to actively growing plants to be effective. Since glyphosate has no soil activity, the area may be replanted as soon as the weeds are dead. Because glyphosate is non-selective, do not apply it or let it drift onto desirable plants. When using herbicides, be sure to read and follow all label directions and pay attention to the appropriate crops and the weeds they control.