Answer: I'm not familiar with a plant called oxtail. There's a weedy plant called Oxalis with trifoliate leaves (much like clover), and there's a plant called horsetail (Equistem) which grows in damp soils and resembles a scouring rush. Getting rid of either is quite a job. Oxalis has thickened roots which store carbohydrates. Even if you kill the tops, the roots will resprout new stems and leaves. It's best to dig these out, roots and all. Horsetail is a primitive plant that sends underground roots great distances from the parent plant. This, too, stores energy in the roots for resprouting. I've had success ridding a slope populated with horsetail by simply mowing it regularly. As soon as new sprouts appear the plant begins to store energy. If you keep the sprouts knocked down, the roots eventually run out of stored energy and die off.
Hope this information is helpful!
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