For The Answer
Saturday, July 24, 2004
By Calvin Finch, Conservation Director, SAWS, and Horticulturist
SAND BUR CONTROL
Because of all the rain sand burs should not be as much of a problem this year as in prior years, but they still can make your yard a torturous place for pets and youngsters.
Sand burs are annual plants that have the prickly burs as their seeds. The burs are spread on our pant legs or the fur of animals that make the mistake of traversing a bed of the plants in late summer or autumn. The burs need well-drained soil in full sun to prosper. They are not good competitors for ground space so, if your lawn is thick or your field is covered by tall growing weeds, they do not survive. Sandy soil that dries out every summer is the ideal habitat, but they can also be a problem in rocky soils and slopes.
The best way to control sand burs on a lawn is to apply a pre-emergent herbicide in March and then again in June. Amaze or XL are often mentioned as effective but other herbicides work well too. Pre-emergent herbicides form a soil barrier that prevents seeds from germinating from 2 to 4 months. For best effect the soil should not be disturbed during the period when the herbicide barrier is at work. Pre-emergent herbicides can be applied to vacant lots and fields as well as lawns but the material is not cheap, and it often takes at least two years to bring sand burs under control. An alternate strategy for vacant lots is to let the wildflowers and other spring weeds stand on the field well into the summer. The weeds shade the ground and prevent much of the sand bur germination. This year with all our rain the weeds were especially lush. The problem with an overgrown field, even if it is spent wildflowers, is that it is unattractive and attracts the negative attention of spouses, neighbors and even code compliance officers. You can put them off for awhile by pleading it is necessary for wildflower reproduction but eventually you will have to mow down the weeds.
Shortly after the weeds are mowed, the sand burs will emerge. If you spray MSMA at this time it will kill the plants before the burs are produced. The MSMA application works best in Bermuda or buffalo grass lawns. You will recognize the sand bur plants because of the finer, green blades in the clumps. Sand bur plants, in fact, are very attractive and often escape control because they are a pleasing addition to a dry lawn or field.
In my vacant lot I find it easier to spot spray Finale or Round-up on the emerging sand bur plants. It kills them quickly if you apply the herbicide when the plants are young.
If you do not catch the sand burs until the burs are formed you can still prevent a lot of misery by “collecting” the mature burs. Visit your local carpet store for a remnant piece. A piece 3 feet wide and 6 to 8 feet long is especially effective when dragged behind the riding lawn mower. It also works when it is dragged behind a teenage boy or girl seeking summer employment. Explain to them that it is an environmentally appropriate way to control sand burs and great exercise at the same time. Maybe they will do it for free!
The carpet piece collects the mature sand burs; the drier they are the more effective the tactic is. After the sand bur season, bury the carpet remnant (deep) or put it in the landfill.
Sand burs are a tough plant to control. They will eventually return, especially in sandy soils. For sand bur control visit www.plantanswers.com.