Sandburs: The best defense is a good offense
February 22, 2007
BY GLEN CHILEK
My introduction to sandburs was back in the summers of my youth when shoes were optional. That's when we discovered that the best ball fields had no grass in the infield and hitting the ball into a sticker patch guaranteed a home run. The best way to solve a sticker patch problem back then was to move the playing field elsewhere.
Today, we don't have the option of moving every time we encounter these "land mines" in our lawns.
PHOTO COURTESY OF MIKE
Cenchrus insurtus, a.k.a. grassburs, stickers or sandburs, are found in abundance in sandy, well-drained soil and wherever they have been allowed to get a competitive edge on more desirable lawn grasses. If you don't have them today, they are still a constant threat. They can move into your lawn by adhering to pant legs, pets, wildlife, or the tires on your lawnmower as you move from area to area. Even topsoil and fill dirt used to "improve" your lawn may be filled with bur seeds waiting to sprout.
To understand how to manage sandburs, let's start by understanding what it is they need to survive. The bur seeds start to germinate in early spring and, under favorable conditions, will continue to germinate until the first freeze or hard frost in the fall. As I indicated earlier, sandy soil, usually equated with well-drained soil, is their ideal habitat for growth, although they can also prosper in rocky or clay soil.
They prefer full sunlight and can adapt to drought. In dry conditions, like we had last summer, they can become semi-dormant then green up and produce seed when the moisture returns. They are normally a warm season annual, but due to our mild winters, can act like a short-lived perennial. They do not compete well for ground space, but a dry summer which most of us had last year, causes stress on desirable grasses and allows the burs to invade.
Now that we know what makes them happy, let's talk about ways to get rid of them. Searching for answers to this question, I came across solutions that ranged from comical to seriously expensive. I'll let you decide.
One old timer told me the best way to clean up grassburs was to run hogs in your front yard - 15 to 20 head per acre should do it. Several sources suggested using a garden tractor or an out-of-work high school student to drag carpet remnants over the infected area. (When you finish, be sure you bury the carpet really deep or take it to the landfill if you try this one.)
Another method suggested pulling or digging the bur plants from your lawn as you identify them. Keep in mind seeds from previous years may continue to germinate there, but after a couple of years, if no more seeds are imported, your sandbur problem will be under control.
Finally, the best solution I came across was a two-step approach: First get control of the problem, then continue to manage it.
First, applying a pre-emergent herbicide in February and reapplying it in April to May will actually kill the young seedlings after germination for two to four months. Products such as Image and Amaze are offered by local nurseries as effective, but other pre-emergent herbicides work well, too, including herbicides that contain the ingredients dithiopyr, pendimethalin, benefin+oryzalin or benefin+trifluralin. The treated area should not be disturbed during this period and should be watered in thoroughly for best results. As always, read and follow label directions carefully. Also remember that it may take a couple of years to eliminate all the burs hiding in your lawn.
In extreme cases, it may be necessary to use glyphosate-based, non-specific herbicides on the grassbur plants, but remember that any drifting spray or runoff can cause damage to your garden plants and turf grass.
Corn gluten meal, an organic alternative, has also shown to have some effect on controlling germinating seeds. Applied at 20 pounds per 1,000 square feet, research shows it has performed erratic ranging from 10-60 percent weed control. Because it does contain nitrogen, it can help the grass, but over-application to increase weed control can be counterproductive, increasing chances of insects and diseases.
Second, creating a good, thick, healthy stand of turf grass will choke out sandburs.
Take the offense with these steps to a healthier lawn:
If it's been over three years since you've had a soil test, or you've never done one, now is a good time. Your county agent has the information and the containers you need for a relatively inexpensive test. Fertilizing can be the best or the worst thing you do for your lawn. A soil test will tell you what the soil has too much of already and what it lacks. Use this information to choose the best type of fertilizer for your lawn and determine when to apply it.
Mow your grass frequently keeping it the proper length. Regular mowing (once or even twice a week) will both encourage a healthy, thick turf growth crowding out potentially germinating bur seeds and will remove sandbur seed heads before they mature and plant themselves in your lawn.
Provide infrequent but deep watering on an "as needed" basis. If your footprints remain visible (the grass does not spring back shortly after being walked on) it needs water. The best time of day to water is early morning. High temperatures later in the day cause a great loss of water due to evaporation.
While grassburs are a dreaded weed, these "good offense" steps should create a healthy lawn with turf grass hearty enough to defend itself (and you) against an invasion of sandburs this summer and next.