Even the most perfectly manicured lawn is likely to contain unseen weed seeds. Some types of weed seeds can remain dormant for a few years before they start to grow. Despite the persistent nature of weed growth, homeowners can keep the unwanted plants under control by the timely application of an appropriate herbicide.
Weeds are generally divided into three categories based on the life cycle of each species. Like an annual flower, an annual weed grows and dies within just one year. A perennial weed can live on from year to year. Although less common in lawns, a biennial weed develops in the first year and produces seeds in the second year. Because of the different weed types, you may need more than one herbicide application.
An annual weed is usually the easiest type to control. A preemergence herbicide can be applied to stop the development of existing weed seeds. The chemicals in a preemergence herbicide interrupt the germination process, preventing the seeds from sprouting. A preemergence herbicide does not affect plants with established roots, so your lawn grass is left undisturbed.
A pre-emergence herbicide should not be used on a recently seeded lawn. To halt the seed germination process, a pre-emergence herbicide should be applied before the growing season begins. Some lawn care products combine a pre-emergence herbicide with a fertilizer for grass growth. Before the growing season is over, however, a different type of weed may try to invade your yard space.
Perennial weeds are generally tougher than annual weeds. Some perennial weeds have a central taproot that grows straight down into the soil. Dandelion is an example of a perennial weed that may go unnoticed until it shoots upward and produces a yellow flower. On the ground underneath the flower, however, lies the unsightly jagged leaves of the dandelion pest.
A post-emergence herbicide can be used to eradicate weeds that have existing root systems. Some post-emergence herbicides are non-selective in regard to which plants they affect, Other post-emergence herbicides are referred to as selective, meaning that you can target a specific type of weed.
If your lawn has a large patch of perennial weeds, you might choose to apply a selective herbicide to the entire area. For a spotty outgrowth of perennial weeds, however, the direct application of a nonselective herbicide might be sufficient.
Maintaining strong, healthy grass can also help constrain the growth of weeds. Contact a lawn product specialist for more information on herbicides and fertilizers.