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Mr. Smarty Plants - Elimination of nutgrass from native flower bed

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Sunday - October 14, 2007

From: Austin, TX
Region: Southwest
Topic: Invasive Plants, Problem Plants
Title: Elimination of nutgrass from native flower bed
Answered by: Barbara Medford

QUESTION:

Nutgrass!*#!* My new bed in NE Austin wraps around a hot sunny SW street corner. Grass wouldn't grow there [I wouldn't water it.] I removed the turf [mostly stickers] to a depth of about 4", carefully sifting the clay soil to remove all roots etc.; then amended with sand. peat moss, compost, et al. I planted lavender, purple fountain grass, Mexican feather grass, a couple of yucca, a couple of retamas, some salvia and an so-far-unused soaker hose. All are thriving ... as is the nut grass. I've dug and dug, trying to get deep enough to eliminate those blasted reproducing 'nuts' and roots. It just gets worse. I'm almost resigned to hand-painting each blade with some toxic, non-specific weedkiller. Are there other solutions? If not, which toxin would you recommend? I don't suppose flaming them with a hand-held propane torch would do any good either. Before my efforts there was no nutgrass there ... or at least it wasn't apparent. Please help!

ANSWER:

We couldn't agree more on your evaluation of nutgrass, as well as the adjectives you have associated with it. Purple nutsedge (Cyperus rotundus) is a sedge native to Africa and central Europe (north to France and Austria), and southern Asia. It is considered one of the most invasive weeds known, having spread out to a world-wide distribution in tropical and temperate regions. The difficulty in controlling it is due to its intensive system of underground tubers and resistance to most herbicides. Tubal dormancy is perhaps the most important of the adaptations that enable nutgrass to persist. That is why nutgrass can re-emerge after you thought you had eliminated it by herbicide or weeding.

Some of the suggestions made by experts on how to control this pest include making sure the drainage of the soil is good. It is also supposed that it can be shaded out by vegetation around it. Populations of viable nutgrass can be dramatically reduced by repeatedly turning the soil at one to two-week intervals to expose the tubers to the sun. Unfortunately, in your flower bed situation, these are probably not terribly practical. As noted above, the tubers are resistant to most herbicides, and if the blades of "grass" are broken off, the tuber carries on, and one to two inches of new growth will be visible within a day. Oh, and it's one of the few plants that plastic mulches cannot affect.

It would appear that part of the reason this nuisance showed up has to do with your bed preparation. You took out grass, with which nutgrass finds it hard to compete. You dug down 4" in the soil, sifting and preparing it for planting. Nutgrass tubers can be as deep as 18", and disturbance of the soil no doubt enabled some of those dormant tubers to get close enough to the now-cleared surface and begin to make themselves known. In other words, you did all the right things to prepare your bed for the new plants (all of which we consider fine selections), and in so doing, also prepared it for the thriving of nutgrass, hiding out in that soil. We know you don't want to hear this, but there is no magic cure. If the soil is kept fairly loose and moist, it will be easier to pull out those long strings of tubers. That is about the only satisfying thing about nutgrass, is that you can get a string of the rhizomes and tubers going, and pull out a bunch in one operation. If you were considering getting on your hands and knees to paint with herbicide, it would be just as easy (and much safer for your other plants) to just pull the !*#!* stuff out. And please, no flaming with the propane torch. You could singe those little blades, and fresh ones would pop up from the tubers protected by the earth. Meanwhile, some of your intended plants could be crisped!

 

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