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Gardening | Keep an eye out for Smilax, a common plant thug

Smilax is an invasive plant and a garden thug.
Smilax is an invasive plant and a garden thug. Courtesy photo

Smilax is a native plant that provides food for more than 40 species of birds. It is an important part of the diet for deer and black bears. Rabbits eat the evergreen leaves and vines. Beavers eat the roots. The thickets it forms make good cover for wildlife.

One species called Jackson vine, Jackson smallii, is a deep-rooted tradition among a number of Southerners who grow the vine ornamentally. It is a must-have climbing up to and across the ceiling of their front porch. It is also a custom to bring the evergreen inside for use as Christmas decoration.

Moreover, tips and shoots are edible and said to be tasty to humans, while small young tubers serve as a source for starch.

It sounds like this plant is suitable for any yard that is a Wildlife Certified Habitat. However, you do not want Smilax in or near your yard. It is an invasive plant and a garden thug.

An invasive plant is one that is adaptable, aggressive and reproduces easily. Typically such plants have escaped from cultivation and moved on to crowd out native plants. Invasive plants many times are a foreign species that, like kudzu, was brought in to solve a problem, or plants that snuck into this country with foreign freight and then spread uncontrolled.

Smilax, however, is a native plant. There are 14 varieties of Smilax in the Carolinas and about 300 to 350 worldwide. Most have thorny stems, some of them fierce, while a few, like Jackson vine, have thorns only at their base or none at all. The plant develops long, underground runners extending from deeply rooted tuber clusters that can weigh as much as 75 pounds.

Rather than escaping from our gardens, Smilax invades them. It grows in and around desirable garden plants, both above and below ground. Its roots interweave themselves among those of desirable plants and shrubs. The thorny vine intertwines within the branches of ornamentals. It grows in sun, part sun and shade, which leaves no spot off limits.

Depending on the variety, leaves are heart- to oval-shaped, some with lobes at their base. They are alternate on the vine and have parallel veins. They are leathery and can reach 5 inches long. Leaf edges are generally smooth, but some species have bristles. Stems are tough, with a profusion of sharp thorns. Homeowners who try to get rid of the plant must use heavy gloves for protection.

Smilax has tiny green flowers, which form clusters and bloom in the spring. Flowers are male or female and attract insects, which pollenate them. Depending on the variety, berries are bluish black, blue or red.

The plant grows along streams and ponds, and on the edge of forests. It climbs with tendrils and grows up to 30 feet high.

Be aware that Smilax can arrive in your yard at any time. After eating the berries, wildlife deposits the seeds in a pile of scat, which provides fertilizer for the seeds when they germinate. Typically the plant starts out undetected. A gardener pulls up a green leaf or too, unknowingly leaving the growing root system behind to spread.

The best way to get rid of Smilax is to dig it out by the roots as soon as it shows up. Digging out an established plant is grueling work because the ever-growing clusters of tubers are anchored by an extensive root system.

The waxy coating on the leaves makes it all but impossible for herbicides, including glyphosate, to penetrate.

Over a period of several years, doggedly cutting Smilax back wears down energy reserves in the plant and eventually deprives its roots of the chlorophyll the plant needs to continue growth.

You don’t want Smilax in your yard. Monitor your weeds and identify them. The application of a broad-spectrum weed killer does not mean that they will disappear.

Reach DEBBIE MENCHEK, a Clemson Master Gardener, at dmgha3@aol.com.