Smilax spp: What to Do About This Thorny Plant

It goes by many names: greenbrier, prickly-ivy, sticker-vine, stay-a-while vine, and cat-brier among others. You may have seen them in your garden—long stiff vines with sharp thorns and gloss, heart-shaped leaves. These are members of the Smilax genus, a group of plants native to the subtropical parts of the world and infamous among gardeners, landscapers, and plant enthusiasts for their prickly thorns and their utter tenacity. While far less common in Canada, Smilax is frequently encountered in the US, Mexico, and the Caribbean among other locales. So what is it, what does it do to your garden, and what can you do about it? Let’s dig in!

Smilax Description and Identification

Unlike many wild plants we’ve discussed here over the years, Smilax species are fairly easy to identify most of the time. Left to its own devices, Smilax will grow into a shrub, forming thick clumps of plants often in wooded areas. It can also climb, and will happily vine up the side of a house, fence, tree, or other structure. It does this by using its thorn-covered stems to “grip” the surface upon which it is climbing. Smilax species often have hooked thorns with stiff glossy light green stems, and darker green but equally glossy heart-shaped leaves. It produces distinct dark red, purple, or black clusters of berries in the spring.

While Smilax is not toxic to people or animals—in fact in many parts of the world it is used as a food plant—we don’t recommend eating it yourself unless you have had expert guidance in how to identify and use it.

Tips and Tricks for Controlling Smilax 

At Gardzen we’re firm in the belief that there are no bad plants, just plants that grow where we don’t want them to. With that said, Smilax is famous for growing where you don’t want it to, and being difficult to remove. Any homeowner or landscaper who has spent an afternoon pulling the thorny vines from a chain-link fence can tell you that it’s not a fun task! So when it comes to Smilax in the garden, there are a couple of different things we can try to control this difficult plant:

• Embrace it! It’s becoming increasingly trendy for gardeners to embrace native plants, even the weeds, and incorporate them into their landscape. And there’s something to be said for the distinctive foliage and berries of Smilax; this is an interesting plant and when trained up a support or over a trellis it does add something. This approach isn’t common or necessarily the best for every garden, but it’s something to consider. And no, you don’t have to keep every individual Smilax plant that pops up in your garden.
• Cut it and/or mow it! A key step in keeping Smilax under control is preventing it from getting established, and that starts by cutting it or mowing it down while it’s still young. The younger vines are less resilient and stiff, so they’re far easier to remove. They also tend to have few if any thorns, which can be downright intimidating on larger or more established plants! By regularly mowing, pruning, and removing Smilax before it takes hold, you’ll ensure that keeping it under control is a much easier task.
• Dig it out! After cutting a plant back, digging out the root crown or rhizomes can help prevent the plant from returning. This must be done carefully and thoroughly, but it really does help. As with cutting or mowing, it’s also best done when the plant is immature and hasn’t fully developed in the soil. Catching it early makes it much easier to remove!
• Chemical controls and herbicides are not especially helpful in our experience—the stiff waxy stems and leaves tend to just shed them, and may cause cascading problems for the birds and insects that feed on these plants. While chemical sprays may be useful in preventing the re-growth of large stands of Smilax if the sprays are applied after the plant has been cut back, we in general recommend other approaches in keeping Smilax out of your garden.

Smilax in the Garden

Smilax is an intriguing plant in its own way: a native that provides food for pollinators and birds but is difficult to control, an edible plant that is also thorny and tricky to manage, and a plant that is both beautiful and disruptive in the garden. It’s neither a good nor a bad thing to have around, but it does need to be managed carefully and perhaps confined to the more wild areas of your outdoor spaces. We hope this blog provides some ideas for dealing with Smilax in your garden space, and if you have tips or tricks of your own we’d love to hear about them!