Here are an organic gardener’s first lines of defense against weeds:
Deny perennial weeds light before you plant a new bed. Since sunlight is food for plants, covering weeds with cardboard or a big plastic tarp for about eight weeks will starve them out, leaving a weed-free bed.
Create optimal soil conditions for your garden plants to put them in a better position to compete.
Soaker hoses and drip lines deliver water to garden plants and leave the spaces in between them—which weeds would seek to occupy—dryer than a sprinkler will.
Mulch restrains annual weeds by denying them the light they need to germinate. Of course, weed seeds that land on top of your mulch germinate and grow like crazy. Nonetheless, consistent mulching will cut annual weeds by about 80 percent.
Hand-pulling weeds builds character and provides great satisfaction—until it becomes a chore that sours a person’s attitude about gardening. Especially novices. Immediately pull anything that is setting seed, and be sure to get the roots or you’ll be wrestling the same plant again in a week or two. Roots come out more easily after a rain has softened the ground.
Close planting shades your garden, so fewer annual weeds germinate. Rather than planting at a wingtip-to-wingtip distance (so that the leaves of any two plants only just touch when they are fully grown), I set them cheek-by-jowl, or about half to two-thirds of the recommended distance. This looks more natural and creates better shade coverage sooner.
Corn gluten applied regularly can keep weed seeds from germinating. Below the Mason-Dixon Line, you’ll have to apply it more often, as heat breaks it down. It’s also high in nitrogen, so it’s best used on lawns; too much N in garden beds can lead to disease and insect infestations.
Organic herbicides such as horticultural vinegar, citrus oil, steam and flame can kill annuals by destroying their leaves, but they rarely damage the roots of perennial weeds. They are also more expensive than glyphosate and may be more hazardous for the person applying them.