1 - Silverleaf nightshade is a common and persistent weed in New Mexico gardens and landscapes.

Yard and Garden October 6, 2012

Q.

I have just cleaned out my garden -- not hard, it did not do much this year. But one of the plants that thrived is a weed. I do not know the name of it, but it is green, leafy, with very tiny thorns on the leaves and stems. I have seen small purple flowers with yellow centers on them if they get big enough. I pull them, but probably do not get the roots. We till our garden each year, usually fall and spring, so I would think the roots would get pulled up. I have not seen this type of weed in any other area of the yard, just the garden. I have not used a weed killer on them as I do not know what that would do to the rest of the garden.

We live in North Albuquerque Acres. These have been a thorn in my side -- no pun intended -- ever since we moved here eight years ago. We were on the west side for many years and I do not remember having these over there.

Any suggestions you may have to get rid of these pests would be most appreciated. Thank you for all that you do.

Jo H.

A.

I think you are describing the silver-leaf nightshade, Solanum elaeagnifolium. This is a common weed with pretty purple flowers and prickles on the stems and undersides of the leaves. The leaves also have a wooly covering and often appear grey or silver, but can also appear greenish when young. Since you are pulling the plants persistently, you may not see the gray color. This weed freezes to the ground each winter and returns from a perennial root system in the spring. Rototilling cuts up the overwintering roots into small pieces which may each grow in to a new plant. These new plants growing from small pieces of root are easier to pull up than those growing from larger roots, so tilling is not a bad practice if you will pull the new plants. The larger ones may be removed by digging deeply. Pulling them up as you are doing is good, but it will take several years of very persistent pulling and digging to have a significant effect on them. Broadleaf herbicides (that kill broad-leafed plants) can help you eliminate the nightshade weeds, but you must use care because they can also harm broad-leafed garden crops and flowers. Many of these can be absorbed by roots of non-target plants in the garden. A glyphosate based herbicide has no soil activity and will be less likely to harm other plants as long as the other plants are protected from the spray. Be sure to read, understand, and follow the directions on the label if you use herbicides. Whether you choose to use an herbicide or to manually remove the plants, persistence is important. The weeds should be treated or pulled within two weeks of their reappearance after each removal. The goal is to prevent the plant from feeding the root system, thus depleting stored foods in the roots and reducing the ability of the weeds to regenerate. This takes time.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

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