Three Types of Weeds
From: DK Books - Lawns
Some weeds will rapidly take over a lawn if they are not dealt with properly. Many of them are more vigorous than grasses and can quickly smother them. Also, weeds such as dandelions can rapidly colonize nearby flowerbeds if they are allowed to spread, and annual weeds often fade away to leave bare patches of soil in the lawn. Finally, some weeds, such as thistles, are uncomfortable to sit or walk on. Knowing what type of weed you are dealing with will help you choose the best method of control.
Although weeds such as groundsel and chickweed germinate, flower, and die within one year, they can rapidly colonize a garden with their large numbers of seeds. It is best to hand-weed them since they have less extensive roots than perennials.
Plants such as Oxalis and buttercups build up a network of bulbils (small, bulblike structures) in the soil, which can be difficult to remove. Chemical weedkillers are often the only effective method of control.
Common lawn weeds, such as dandelions, daisies, and thistles, appear year after year. Most have extensive root systems, making them hard to eradicate — remove the entire root; any pieces left in the ground will regrow.