The key to controlling weeds is keeping them from flowering and producing seeds.
Mulch to save water and slow weed growth
A thick layer of mulch over drip irrigation is an excellent way to reduce weeds in your garden. Weeds that do pop up out of the mulch are often easy to pull.
With or without drip irrigation, mulching is a good idea, especially when we’re all trying to save water. Mulch keeps the soil underneath moist, and organic mulches such as compost, leaves, wood chips, and straw contribute organic matter for soil organisms to feed on.
Particle size will determine how thickly you apply the mulch. For weed control, apply coarse-textured mulches, such as bark and wood chips, 4” deep. Apply fine-textured mulches, such as shredded leaves or dry grass clippings, about 2” deep. Keep all mulch several inches away from the stems of plants or the trunks of trees and shrubs to prevent disease.
Established perennial weeds take more work. If you can’t pull or dig up the roots, cut the plant down and cover the crown with a thick layer of mulch. Cut down any new shoots and don’t allow the plants to flower, produce new leaves, or go to seed. With no leaves to photosynthesize energy, the roots will eventually use up their reserve energy, stop sending up new shoots, and die.
All organic mulches break down over time, some quicker than others. You’ll need to re-mulch every two or three years.
Weed by hand
Weeds are easiest to pull—by hand or with a weeding tool—when plants are young and the soil is moist, but not wet. If they haven’t flowered, and if the weed plants don’t reproduce from plant fragments, tubers, or bulbs, you can put them in your compost.
Products containing clove oil or soap will kill the above-ground parts of weeds, but will leave roots that may sprout again. These herbicides will be most effective on young plants. Killing older annual weeds or tough perennials may require several applications.
Caution: When spraying any kind of herbicide, protect desired plants from coming into contact with the spray. Do not spray on windy days. Keep people and pets away from the area until the herbicide has dried.