Sandbur Control Part 2
As mentioned last week, even the best herbicide program is not enough to keep sandburs under control. The turfgrass must be strong and healthy so it is better suited to out-compete this pesky weed. This begins with proper fertility. As the name might imply, sandburs are usually a bigger problem on sandy soils. All else being equal, sandy soils do not retain water or nutrients as well as heavier soils, and are more likely to be low in key nutrients. Dry soils low in phosphorus seem to be especially prone to sandbur infestation.
A basic soil test can establish baseline information for nutrient levels, especially phosphorus and potassium. Once these nutrients are brought up to an adequate level, nitrogen will need to be applied on a regular basis to support turfgrass growth. Rainfall or irrigation is a critical player here as turf grass should not be fertilized unless enough water is present to move the fertilizer down into the soil and provide enough water for basic plant function.
It is also important to note that nitrogen will move freely through a sandy soil with excess rainfall or irrigation, causing potential groundwater contamination. Lighter, frequent applications of nitrogen are preferable to heavier rates. Slow release nitrogen fertilizers are also helpful.
Needless to say, keeping sandy soil as moist as needed to support proper growth can be difficult to do, especially during periods of drought. Think back with me to the summers of 2011 and 2012. Horrible drought conditions led to an environment that discouraged turf growth, allowing sandburs to gain the competitive advantage. Hopefully, we are not headed back into drought conditions that bad, but it has been a dry winter, and those two brushes we had with zero degree temperatures could slow the greenup on desirable turfgrasses. We will have to wait and see for sure, but it could be another especially bad sandbur season.
Sometimes, sandburs can develop in small pockets throughout a landscape. Learn to look for these and hoe them out early before the seeds mature. The seeds are the “stickers” and are mature when they turn brown and fall easily from the stem. Regular mowing before seedheads form is also beneficial. This also helps discourage these weeds in another way. By regularly mowing bermudagrass at a lower height, the turf becomes more dense, giving it a competitive edge against the weed.
I hesitate to even mention this next suggestion, simply because it is so difficult to accomplish. The better you can contain sandburs to a given area, the better your chances of success will be. While we generally discourage bagging clippings, in this case it is not a bad idea, especially if the seeds have been allowed to mature.
It is a common practice for people to drag old carpet or rugs around in hope of collecting the seeds. While this can certainly reduce the numbers present, it may be doing more harm than good by spreading the seeds to a wider area.
This is a tough problem that requires consistency and patience. However, success is attainable. Just remember that seeds can remain viable in the soil for several years so continue with those herbicide programs as we discussed last week, even if you think you’ve eliminated them.
For more information on this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at firstname.lastname@example.org, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.
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