In the sandy soils that inherently come with gardening near the coast, one of the most annoying weeds actually thrives in our sand. I’m talking about burr grass! Some people have other names … grass burr, burr weeds, cockleburs, sand spurs. But whatever you call them, they’re a big pain in the sand.
So, what’s a gardener to do? While there’s no “silver bullet” — some kind of magical herbicide — there are some steps we can take to make it less attractive for these weeds to take hold.
It’s a four-step process that begins with adding humates or humus. Then, the use of nitrogen-rich (or nitrogen-only) fertilizers, sticking to a specific fertilization schedule, and gathering up as many of the burrs as possible.
Let’s start with the addition of humates. There are several forms of humic acid on the market. I prefer the granular kind that can be put out easily with a broadcast spreader. The liquid versions are just as effective, but not quite so cost-effective. The liquids are always more expensive and cover less square footage. The fact is that burrs hate a humate-rich environment, so apply humates on a quarterly basis the first year, then one to two times every year after that.
Another thing burrs hate is a nitrogen-rich environment. This does not mean you should use “high-nitrogen” fertilizers. It means you should use nitrogen-rich or nitrogen-only fertilizers. The most basic example is always available at nurseries, garden centers and feed stores. And the most cost-effective are ammonium sulfate formulas that usually have a nitrogen-phosphorous-potassium (N-P-K) ratio of 21-0-0. There’s also a new organic formula known as Sweet Green from Nitro-Phos Fertilizers. It has an organically-based N-P-K of 11-0-4, and that’s perfectly fine for the nitrogen hit needed.
The next step in the equation is to stay true to a smart fertilization schedule that calls for slow- or controlled-release fertilizers and the consistent use of pre-emergent herbicides to block weed seeds from germinating. My fertilization schedule is perfect.
The final step is the most annoying, and I completely understand why. It’s the process of gathering up as many fallen burrs (the seeds that will likely germinate again) as possible. Unless you want to kick around in layers of tube socks so the burrs can hitch a ride on your feet and ankles, you need a clever way to get them out of the yard, right?
The two most common methods involve a typical wet-dry vacuum or burlap bags.
Use the vacuum to suck up as many burrs as possible. You’ll never get all of them, of course, but the few left behind will be more easily controlled with the pre-emergent herbicide. Do this before you do the humates and fertilization, so you don’t suck up all the good stuff.
The burlap bags come into play in the tow-sack method. Drop something into the bag to weigh it down, then drag it around by hand or pull it along behind a riding mower or tractor. Once one side of the bag is covered, flip it. Then you can turn it inside out and go through the process again. Once you’ve used the burlap to its maximum, just throw it away.
So, all this may sound a bit tedious, but once you’ve done everything on the list, you will see a remarkable difference in as little as three to six months.
And by the way … I’m aware that “cockleburs” are completely different, botanically-speaking, than burr grass. I’ve just used that term here because many people use that name synonymously with burr grass or grass burrs.