8/28/10 - In the beginning, there was cocklebur. I spent several weeks during the summer of 2009 cleaning it up where it was getting ready to consume the planet from the fill in our New Mexico power trench. I harvested all the burs I could find. Then I whacked down the big plants only to discover they grew right back. I found that digging up plants in this rocky, dry soil is futile. Like dandilions, cockleburs like nothing better than to have you sever their tap roots, from which they regenerate for the remainder of the growing season (cocklebur is an annual) and are capable of producing their disagreeable fruit.
I resorted to poisoning the plants and pursued them with Ortho Weed-B-Gon for the rest of the summer.
Now, growing vigorously on the north and east sides of the house, there is the New Mexico variation of a weed I know from hiking in the space between the hardwood forests and the agricultural fields in Virginia. The weed is horse nettle. Horse nettle is a member of the nightshade family and not a true nettle, but has a disposition as noxious as cocklebur. New Mexico's horse nettle (Solanum elaeagnifolium) resembles Virginia's variety (Solanum carolinense), but is different enough that I didn't recognize it until I got a heads up from our neighbor, Jean. She gently advised "You might want to control this stuff. It's horse nettle. It'll take over."
In New Mexico, horse nettle is a pretty weed, with brighter purple flowers than Solanum carolinense has and long silvery leaves, gently indented and leathery. I notice online that some folks are cultivating horse nettle as a garden plant. They will likely live to regret it, unless the cultivated variety behaves differently from the weed.
The nettle part of the plant, whether in Virginia or New Mexico, grows along the stems and is hard to see. If you attempt to pull up a plant from a stem, you get a hot and amazingly painful stab, even through gloves.
You can grab the plant just below the soil and avoid the nettles, but pulling up the plant extricates only a chunk of the plant's aggressive perennial and wide-spreading root system. The plant will quickly regenerate from what remains under the surface. If you dig the plant up and sever the root, leaving two or more parts underground, you'll soon have two or more healthy and enthusiastic plants. Everybody knows these things except me, but I'm learning.
My organic gardener's soul regrets to say that Weed-B-Gon is the answer.