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Garden Q&A: Controlling horse nettle and coping with herbicide injury

Garden Q&A: Controlling horse nettle and coping with herbicide injury
To control horse nettle in a garden, a systemic herbicide such as glyphosate must be used. (Ellen Nibali / HANDOUT)

Horse nettle is spreading in my flower garden. I clip off the yellow berries when they appear and try to pull out plants, but they break off and roots remain in the ground. My control methods are not working.

Continue your tactics to weaken and prevent seeding of this prickly member of the nightshade family. Horse nettle spreads primarily through deep rhizomes. Spray or paint the plants with an herbicide containing glyphosate. This is a total vegetation killer, so shield desirable plants. A systemic herbicide, glyphosate is transported throughout the plant and into the roots. Wait two weeks to give the chemical time to reach the roots. Let plants totally brown out before pulling or digging. Hard to kill perennial weeds with established root systems often respond best to late summer-early fall systemic applications when they are transporting reserves to their roots for winter. Keep herbicide use to a minimum.

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I went on a trip and came back to a messed up veggie garden with something affecting 90% of tomato plants and about 50% of the pepper plants. The leaves of both turned very dark and feel like leather, with raised bubbles on old leaves. New leaves are not forming properly and have a weird fern-like in appearance.

Your veggies’ symptoms — plus curling, twisting and under-sized leaves — are consistent with herbicide injury. Lately we’ve gotten photos and questions similar to yours, perhaps because of the breezy weather. Even if you and your neighbors don’t use herbicides, herbicide sprays such as 2,4-D can drift 1/4 mile and land on plants. Herbicides also can travel with stormwater or irrigation run-off from lawn areas treated with herbicides, including “weed & feed” products. Tomato is especially susceptible to this type of herbicide injury. Most likely, your tomato will not grow out of the injury to produce a decent crop. It may be hard to find transplants in stores this late in the growing season. Suckers from friends’ plant can be used to start new plants. Suckers at the base with roots will establish more quickly. You must keep them well-watered. Plant them in pots until they root, then plant them in the garden, or plant directly in the garden. Pepper is less susceptible to herbicide injury and will probably outgrow it.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Maryland’s Gardening Experts” to send questions and photos.

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