In warmer climates, some annuals such as crabgrass can live into a second year. Biennials live for 2 years. The first year's growth is vegetative, usually as a low cluster of leaves. During the second year a flower stalk arises and produces seeds, and the plant dies. Mallow is an example of a biennial weed.
Perennials live and produce seeds year after year.
Many perennial plants, such as Bermuda grass, also reproduce by vegetative means. When underground rhizomes or above ground stolons break off from the mother plant, each new section develops roots and leaves and becomes a separate plant. Lawn weeds are further classified as either broadleaf or narrowleaf . Broadleaf plants emerge from the soil with 2 small leaves, narrowleaf plants start out with a single leaf. Dandelion, mallow, and plantain are typical broadleaf weeds.