Difference Between Annual & Perennial Weeds

Life Cycle Duration

• Annual weeds are those that sprout, grow, flower, set seed and die within one calendar year or growing season. Depending on species, an annual weed may grow in warm, frost-free months or in the cool days of fall through spring. Perennial weeds return year after year. Often an extensive or large root system facilitates the weed's return after a drought or cold winter dormancy. Some weeds are biennial, growing one year with lots of leaves and then flowering, seeding and dying the second year.

Weed Examples

• Common annual weeds in gardens and lawns in the United States include chickweed, crabgrass, knotweed, lamb's quarters and pigweed. These weeds spread by seed production. Perennial weeds such as Florida betony, dandelion, nutsedge, violet, clover, wild garlic, quackgrass, woodsorrel and plantain persist by both seed and sprawling roots, multiplying bulbs and horizontal stems called stolons.

Management Insight

• Since annual weeds grow quickly and do not develop large, persistent root systems, they often are much easier to control by hand-pulling and hoeing. Annual weeds proliferate in landscapes where plants continually flower and set seed. By removing annual weeds before flowers form, the number of seeds that can germinate diminishes over time. Pre-emergent herbicides prevent seeds from germinating. Perennial weeds can infiltrate a garden by first establishing as a germinating seed or from sprawling roots in a nearby colony. Hand-pulling and hoeing may work in control, but if parts of the root system remain, perennial weeds regrow. Chemical and pre-emergent herbicides in tandem help diminish perennial weeds in a garden.

Recommendations

• Purdue University recommends that the best approach to weed control and pesticide application in a landscape is the most conservative one. Employ non-chemical means initially. This includes hand-weeding and hoeing, modifying irrigation to benefit garden plant growth and not the weeds, and using groundcover mulches to choke out or prevent weeds from establishing. Always remove weeds before any seeds form. Chemicals serve a purpose, but start with the least toxic options or by localized spot applications rather than widespread herbicide application.