Examples of perennial weeds include dandelions, thistles, and daisies. These weeds develop massive, complex root systems, which enable them to come back every year. They are very difficult to get rid of because even after removing the root, if anything is left over, the entire system will regrow.
Examples of annuals include chickweed and groundsel. These weeds may take less than a year to germinate, flower, and die, but they can spread seeds quickly and take up a possessive residence in your lawn or garden.
Examples of bulbil-producing weeds include Oxalis and buttercups. These weeds are so named because they produce networks of miniature bulbs that usually must be killed with chemicals.