By Jeff Floyd
Certified horticulturist and arborist
I know you hate those weeds in your lawn, but they’re trying to tell you something, and in this case, you really should shoot the messenger. A lot of lawn problems can be solved simply by identifying the weeds it supports. The reason is that all plants have unique growing conditions as well as limitations. You can apply this knowledge to determine if your lawn needs more fertilizer, less water, and even if it needs dethatching or aeration.
Dandelions may signal a compacted soil. This perennial weed has a slight advantage over other plants in soils that are densely packed on the surface. Its deep taproot allows the dandelion to take advantage of the more readily available nutrients and oxygen below the compacted surface. On the other hand, the shallow roots of grasses in compact soils are unable to take up enough oxygen and the tightly packed soil particles create a physical barrier to their lateral development.
Crabgrass doesn’t mind dry hot soils. In the heat of summer, it will be perfectly content while nearby lawn grasses slowly fade away. The presence of crabgrass may also be telling you that your soil is compact. However, it doesn’t have a taproot like a dandelion. Instead, crabgrass has a very low need for nutrients allowing it to take advantage of exposed compact soil. It also thrives in extreme pH ranges, where both alkaline and acidic soils tie up nutrients.
Nutsedge loves water. The first step to controlling it is to make sure you’re not overwatering. Pigweed may be trying to tell you to stop applying fertilizers with potassium. Annual bluegrass (poa) will happily grow alongside algae in an overwatered area. Chickweed, knotweed, and spurge will be as happy as dandelions in compact soils. Black medic and wood sorrels grow well in soils that need nitrogen.
There are dozens of books and websites to help you identify weeds visually. One great site is the Texas A&M turfgrass page at aggieturf.tamu.edu. You can use the linked images on this site to identify your weedy pest. After determining what you’re dealing with, you will be able to develop a strategy for having the best-looking lawn on your block. We’ll get into that next time.
