For Release September 15, 1998

Too Late for Sandbur Control This Year

AGRI-VIEWS
by Chuck Otte, County Extension Agent

It never seems to fail. You’re out for a walk along your driveway or the back side of your property. You come back into the house, reach down to untie your shoe laces and wham! You’ve got a fingerful of sharp thorns from half a dozen sandburs caught up in your shoe laces. If you think that feels bad think about how your dog feels with a few of those in his fur or paws!

Sandburs are a fairly common grass in this part of Kansas. Yes, I said grass. We’re talking about field sandburs here. Not the plant with little yellow flowers that vines out all over the place but only grows a few inches high. That is puncturevine and is fairly easily controlled. We’re talking about field or grass sandburs.

Up until the time sandburs head out, most people just assume that they are some other grass. Sandburs, like crabgrass and foxtail, are an annual grass that dies each fall with the frost and starts new every year from seed in or on the soil. The ground has to warm up above about 55 degrees before sandbur seed will sprout and grow. But if it is dry or there is too much shade from desirable grasses the seed will lay dormant, sometimes for a couple of years.

So there lays the sandbur seed just waiting. Then we hit a dry spell in July, the other grasses go dormant and sunlight gets to the soil surface. Then we have a nice little ¾ inch shower and before you know it the sandbur has sprouted and is growing. But you don’t know it because it just looks like any other blade of grass greening up after the rain. Sandburs can sprout anytime from April through August and even the late sprouting seeds can produce seedheads before frost.

By the time the plant has produced burrs so that you know where it is, it is too late for chemical control. If you are patient, careful and ruthless you can go along and pull up the plants. Be careful not to dislodge any of the burrs and place all the plant in some container that you can throw away or burn. If you do this relentlessly for two to three years you will probably get rid of most of your sandburs.

Many people aren’t willing to go through that much work though. First of all be sure to carefully go around and mark all the areas where you have sandburs this fall. If you have them there this year, you’ll have them there next year. Now, next spring in early April go out and spread crabgrass preventer in this area. Make sure it gets watered in within seven days to be activated. Read the label carefully. If the product you are using says to reapply in eight to ten weeks, or whatever time length, mark it down on the calendar and be sure to do it. With the ability of sandburs to sprout and grow late you need to make sure you have full season control. Some of the newer crabgrass preventers that contain products like Barricade and Dimension will probably not require a re-treatment because of their long lasting control.

But you aren’t quite through yet. Most crabgrass controls will miss some sandburs so a post-emerge application will be needed. In mid-June, mid-July and mid-August you will need to use one of the post-emerge crabgrass or nutgrass controls. These products are burn down chemicals that work best when it is hot. The perennial grasses, like fescue and bluegrass, can tolerate the burn down but annual grasses are usually killed. Plan on two treatments seven days apart for each of these monthly treatments.

This series of treatments will need to be done for at least two years, three is you had a serious infestation. Then take a year off and see if any show up. Sandburs are a pain, literally! But with a dedicated approach they can be controlled through either a chemical or non-chemical approach, but you have to be dedicated!

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