Spring is here and so are the weeds. With our unusually early warm weather, it seems the unwanted and out-of-place plants have doubled their population this year. Within the last few weeks, there have been many lawns in Washington County that have been plagued with weeds. There have been some weeds with small white flowers such as Hairy Bittercress and Shepherd’s Purse, and others with purple flowers such as Henbit or Deadnettle.
All of these weeds, as well as others, have done well this year because of droughts from previous years and a mild winter this year. In past, drought stress killed patches of grass which opened up space for weeds to invade. These established weeds were able to thrive because of recent weather.
The best defense against any of these weeds is to exclude them from your lawn by not providing them space to become established. This is accomplished by creating a healthy lawn. It is a process that will take some time. To start this spring, replant any bare areas; maintaining the proper mowing height for grass; and take a soil sample for analysis to properly fertilize.
Replanting is accomplished by removing any dead grass and weeds, loosening the soil, planting seed and watering to establish the grass. While best results are achieved with fall plantings, spring can be a good time to replant bare patches, however, overseeding in the fall would also be recommended.
Determining the proper lawn height depends on the type of grass. In general, if your entire lawn turns brown during the winter (because of temperature) and stays green during the summer, you likely have a lawn of warm season grass such as Zoysia or Bermuda grass. These grasses should be mowed at a height of a half inch to 1 inch. If your lawn is green most of the year, you likely have cool-season grass. These grasses should be mowed to 3 1/2 inches. The advantage of keeping your grass on the taller side is that it helps to shade the weeds.
A soil analysis should be conducted every three years to determine what type of amendments you need to add to your lawn in the fall. Soils that are out-of-balance might inhibit the ability of the grass to grow and develop a nice root system, and may encourage weed growth.
As you are working to re-establish your lawn, try to remove weeds as soon as you see them and certainly before they produce seeds. It is easier to remove one weed this year than it is to remove 50 or more next year. If hand pulling is impractical, herbicides are available. However, before buying a herbicide it is important to identify the weed you are trying to kill, as some herbicides work better on certain weeds. It is also important to make sure the product is labeled for your particular weed. Always, use herbicides according to their label.
For weed identification, go to www.hgic.umd.edu. Click on Plant Diagnostics, Lawns, and then Weeds. Or contact Karen Sechler at University of Maryland Extension- Washington County at 301-791-1604 or firstname.lastname@example.org.
Karen Sechler is a horticulture educator with the University of Maryland Extension in Washington County.