Grass Burs Control

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Grass burs are an annual grassy weed. It is important to realize they are an annual. The grass bur needs a seed to create new plant and not a rhizome.

The life cycle of these plants are:

1. Burs or seeds germinate in spring, a grass like weed will develops in the spring and summer
2. Unknowingly the home owner probably mows the grass bur plant along with lawn grass.
3. As summer heats up the grass bur will began to produce burs
4. From the middle of summer to frost the burs are present catching a ride on everything that comes by. The burs (seeds) have a germination life up to 7 years.

For the home owner, the weapons for eliminating burs are very limited. Currently no consumer product is on the market that will kill out the grass bur without killing the lawn grass as well. A commercial agricultural product could be available. These product can only be used by licensed applicators and not available for home owners.
The weapons you do have available:

#1 – a preemergent weed killer that must be applied in early, long before the burs germinate. Application of preemergent is critical and is timed around the average last killing frost:
for Parker County the last average killing frost is March 17 – 20th.
For preemergent application use a two week window… Application should be March 1-15th. If the weather is still such that the freezing temps have not let up by early March, the date can be pushed forward. The same goes, if the weather is warming up early. Move your application date back. Getting the granules on ground and watered in several days before that last killing frost is the critical part. Preemergent has about 2-4 week window to work its magic.

#2 A second application is required 90 days later. This is a critical application. If this application is not applied in a timely manner, time and money have been wasted. The second application of preemergent must be in the June 1 – 15th window. Again, water to activate the granules. Only use preemgerent granules. Do not combine with fertilizer or use any ‘weed and feed’ type of product as it is not effective in our area because of temperature.

If you are dealing with grass burr in the summer or fall of the year, bag your lawn cuttings. Only compost the clippings in a hot compost pile, or burn, or bag and send to the landfill. Using an herbicide after the burs are formed is not going to help with next year’s crop of burs, but it could eliminate additional burs from being formed. The products that will kill grass burs will also kill the turf grass. A way to capture as many of the burs or seeds as possible is to drag an old blanket over the area, then dispose of the blanket.

Just an added note: Several of the Master Gardeners have found increasing the fertility of their soil by using compost, and a high nitrogen fertilizer on a regular bases has eliminated many of their grass bur and weed issues.