Weeds Explained Guide to Types Life Cycles and Control

By Andi Anderson

Weeds are simply plants growing where they are not wanted. A corn plant is valuable in a corn field, yet the next year it can become a volunteer weed in soybeans. In a flower bed, a surprise tree seedling is a weed too.

Farmers and gardeners use several tools to reduce weed competition: good cultural practices, mechanical cultivation, and carefully chosen herbicides. The same multipronged approach works well in home gardens.

The best time to control weeds is when they are small. Farmers sometimes use early season tools such as rotary hoes, often essential for organic farms. Herbicides are used in different ways.

Pre emergent products must be in place before weeds sprout. Many selective post emergent labels require treatment before weeds exceed a set height, often about four inches.

Non selective products act on most green plants; glyphosate is a common example. Crops that quickly form a full canopy often outcompete weeds by shading the soil.

Knowing weed life cycles guides smarter control. Summer annuals sprout in spring, set seed, and die before winter, such as foxtails and crabgrass. Winter annuals sprout in fall, live through winter, and finish in spring, including chickweed and henbit.

Biennials form a rosette the first year, then flower and seed the second; wild carrot and bull thistle fit this pattern. Perennials grow for many years from underground roots or stems, so they can regrow after tops are removed. Canada thistle and dandelion are examples. Chemical control of perennials is most effective in fall or at flowering.

Weeds also differ by type. Grasses have narrow leaves and round stems. Broadleaves have wider leaves with netted veins. Sedges look like grasses but usually have a triangular stem, and grass herbicides rarely control them.

Remember invasive species as well. Garlic mustard, callery pear, and Asian bush honeysuckle spread aggressively and threaten natural areas.

Use integrated pest management. Combine mulching, hoeing, and hand pulling with smart herbicide choices. Mow lawns at three inches to help turf outcompete weeds. Before planting, tarp a bed for two weeks to reduce seedlings. Choose methods that match your goals and values.

Photo Credit: gettyimages-zoomtravels