How To Kill Vines That Have Thorns

An unwanted vine with thorns leaves a gardener in a prickly situation. Whether the vine is an unwanted guest in the landscape or an ornamental planted in the wrong place, trying to get rid of it can result in scratched-up arms and legs. To avoid this, do some prep and use an herbicide if you have to.

There are a wealth of vines with thorns; some are considered invasive and can take over native habitats, but others are planted for their ornamental value. Regardless of whether the vine was once a desired landscape addition or has invaded your landscape on its own, now it's a spiky weed that might be taking over your desirable plants.

For example, bougainvillea (​Bougainvillea​ spp., USDA zones 9b to 10a) is an ornamental vine with thorns that puts on a stunning display of robust color when in bloom. If planted in an area where the vine interferes with traffic or needs constant pruning to keep it in check, however, it can become a nuisance.

Another vine with thorns and a more invasive nature is greenbriar (​Smilax laurifolia​, USDA zones 7 through 10). This evergreen perennial is part of the ​Smilax​ genus and has thorny stems and waxy leaves with a root system that's difficult to remove. When left unchecked, greenbriar can quickly grow into a large, tangled mass of thorns that takes over trees and other plants.

Depending on its size and the extent of its root system, you may be able to remove the vine with thorns by digging it out. However, before you grab your shovel and pruners, you'll want to protect yourself. Don protective clothing like a long-sleeved shirt, long pants, closed-toe shoes, thick gloves, and protective eyewear.

Tools like a spade shovel, loppers, hand saw and hand-held pruners will work well to get the job done. You'll first want to cut the vine's canes down so you have a manageable size plant to work with and you can access the vine's crown. At this point, you can dig it out of the ground, making sure to get the entire root system. If you don't remove all the roots, you run the risk of the vine growing back.

If you're dealing with a large woody vine that's too difficult to remove by digging, you can use an herbicide like glyphosate to finish the job of killing it and stopping future growth. Once again, you'll want to wear protective clothing and eyewear so you don't get torn up by the thorny branches. Cut the vine's branches close to the ground and then immediately apply a full-strength solution of glyphosate to the cut portions. So you don't get the herbicide on desirable plants, use a paintbrush to paint the herbicide over the cut ends of the branches. Keep an eye on the vine for signs of new growth and reapply the glyphosate if needed, as it may take several applications before the vine is killed.

Keep children and pets out of the area until the herbicide completely dries, which can take several hours. If spraying, don't use it on a windy day or when rain is forecast and be sure to store the herbicide out of the reach of children and pets. Remove and wash your clothing after the application.