Regardless of the growing conditions - too dry, too wet, too hot, too cold - weeds in the garden seem to flourish. When the growth of our crops and flowers slow down due to stressful growing conditions, the weeds take over. There are several reason why we need to keep weeds under control in our flower and vegetable gardens. Weeds are strong competitors with garden crops for available water, nutrients, and sunlight. As the weeds grow tall, they shade the flowers and vegetables, resulting in spindly, unproductive plants. Reduced air circulation created by tall weeds encourages the development and spread of foliage diseases, such as early blight and septoria leaf spot on tomatoes. Also, a weedy garden often has more insect problems.
The best time to control weeds is while they are small. Unfortunately, this requires repeated cultivation through the growing season as weed seeds continue to germinate during the spring and summer months. The young seedlings are more vulnerable and easy to uproot with a hoe or cultivator. The larger the weeds become, the more difficult they are to remove with a hoe and will require pulling by hand. Some weeds, such as crabgrass, become very difficult to remove from the garden after they have become established. Crabgrass forms roots at nodes along the shoots, giving them a firm hold in the soil which make them very difficult to hoe or pull out. Use care when pulling large weeds that are growing close to desirable plants because the roots of the weed and the other plant may be intertwined. You may uproot both plants by accident.
There are essentially two types of weeds in our gardens, annuals and perennials. Annual weeds grow rapidly, flower, set seed and die in a single season. A few examples of common annual weeds are: crabgrass, velvetleaf, purslane, knotweed, lambsquarter, and foxtail. It is very important to destroy these weeds while they are small, before they produce thousands of seeds, guaranteeing a weed problem for many years in the future. If these weeds have taken over your garden and you can't hoe or pull them out, mowing may be an option. This will reduce the height and slow or prevent flowering and seed formation. However, some low-growing weeds, such as crabgrass and purslane, will elude the mower.
Fleshy-leafed purslane also presents another problem. It should be pulled and removed from the garden. If cultivated and chopped into several pieces, each of the pieces may root and become new weeds, increasing the problem.
Perennial weeds, such as dandelions, quackgrass, thistle, and plantain return each year to flower and produce seed. Like annual weeds, these plants are easy to control when in the seedling stage. However, once they become established they are very difficult to control because of their perennial root system and rhizomes. Quackgrass and thistles not only spread by seed, they invade a garden with underground stems called rhizomes. Hoeing and cultivating mature plants will chop the rhizomes into small pieces and each section will become a new plant, multiplying the problem.
These weeds can become a serious problem in perennial garden areas, such as a perennial flower garden, asparagus, strawberry, and raspberry plantings. An option for control of a serious quack grass or thistle problem may be to spot treat the weeds with a non-selective herbicide such as glyphosate (Roundup, Kleenup, or Kleeraway). These products will kill virtually anything green they contact as the compound is translocated throughout the root system of the plant. They can be applied with a "wick applicator" or sponge and wiped onto the leaves of the weed or sprayed with a fine stream.
Once weeds are removed and under control, a good layer of mulch will help reduce future weed problems.
This article originally appeared in the August 8, 1997 issue, pp. 126-127.
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