If there’s a bare spot in your garden, a weed seed will find it. Weeds aren’t bad plants; they’re just plants that are growing where you don’t want them to. Some weeds are easily removed by hand. Others are persistent about growing back and become more and more difficult to eradicate the longer they are left to establish themselves and spread.
Annuals vs. Perennials
Just like plants you intentionally grow in your garden, weeds can be annuals or perennials.
- Annuals are plants that sprout from seed, grow for a single year, and then die. Typically, annual plants produce many seeds that can germinate to produce more plants the following year.
- Perennials, by contrast, are plants that live two years or longer; perennials can be short-lived or long-lived. They establish robust root systems and re-grow from the same root system year after year.
In general, it's much easier to eradicate annual weeds than it is perennial weeds.
Annual weeds spread by seed. They can self-seed or the seeds can be brought into the garden by birds, four-legged animals, or by sticking to your clothing. Examples of annual weeds include chickweed, crabgrass, knotweed, lambs-quarters, common mallow, pigweed, purple deadnettle, groundsel, nettle (common), purslane, speedwell, spurge, and yellow wood sorrel (oxalis).
Just as with other plants, weeds can be cool-season or warm-season annuals.
- Cool-season annual weeds sprout any time from fall through spring and some grow even through the winter months. They’ll go to flower in late spring / early summer. The weed might disappear when the weather warms, but you’ll see even more of them germinating the following fall.
- Warm-season annual weeds tend to start growing in the spring and hang around all through the growing season. Either way, the only way to control them is to remove them before they go to seed again. Annual weeds very often have shallow roots and can be easily hand-pulled or cut off with a hoe.
Hopefully, you will see fewer and fewer annual weeds as the season progresses. The reality, however, is that new seeds will always find their way in and some seeds remain dormant in the soil until ideal conditions present themselves and they germinate. Weeding is an ongoing process; if you can get in the habit of removing weeds each time you work in your garden, it won’t become an overwhelming task.
Perennial weeds are the most difficult to control. They spread by seed and creeping roots and if you don’t pull the entire root, the plant can actually reproduce from every piece of root left behind. You’ll have similar problems with perennial weeds that grow deep, hard-to-remove taproots.
Hoeing and tilling are not good choices for removing perennial weeds. Hand weeding will work if you are very thorough about removing the entire plant and its root system. If you can handle cold temperatures, perennial weeds pull out most easily in the early spring, when the ground has recently thawed. Sometimes an herbicide is the only solution for eradicating tough perennial weeds like poison ivy, ground ivy, and brambles.
Examples of perennial weeds include bindweed, burdock, dandelion, dock, ground ivy, horsetail, Japanese knotweed, plantain, poison ivy, quackgrass, thistle, and ragweed.
Lawn Weed ID and Management. University of Maryland Extension
Perennial Weeds. University of Minnesota Extension