Smilax: Nothing to smile about!

- by Karen Fineran 

Family: Smilacaceae

Genus: Smilax 
Species: bona-nox


    Has your garden been invaded by an ugly, thorny, dark green, waxy, heart-shaped vine?  Is it sending up shoots in various places throughout your oleanders, wrapping itself around the root systems of your azaleas, and climbing high into the oaks with its thorny brambles?  

    This is Smilax, aka Greenbrier, aka Catbrier, aka Cowvine.  Although Smilax is a native plant to the eastern and central United States, and it provides berries and shelter for birds and other animals in the wild, this is one neighbor that you may just want to send packing from your garden – even if it requires months or years of persistence.

    Smilax is a genus of about 300-350 species, found in temperate zones, tropics and subtropics worldwide.  On their own, Smilax plants will grow as shrubs, forming dense impenetrable thickets. They will also grow over trees and other plants up to 10 meters high, their hooked thorns allowing them to hang onto and scramble over branches and fences. The stems have sharp spines that can really give a beating to your hands when you try to pull the vines down from the trees or pull them up from the ground.  Put those gloves on!   

    This aggressive and fast-growing vine is incredibly difficult to eradicate.  Smilax is a very damage-tolerant plant capable of growing back from its rhizomes after being cut or burned down.  This, coupled with the fact that birds and other small animals spread the seeds over large areas, makes the plants very hard to get rid of.  The seeds that pass from the birds can remain viable for long periods of time, and then germinate when the conditions are right.  As these seeds germinate best after being exposed to a freeze, perhaps the hard winters the Coast has experienced lately have exacerbated the vine’s spread.

    This nasty nuisance can spread all over your yard or garden from extensive underground tuber/rhizome systems and sprawling, clambering vines above ground.  The rhizomes are attached to hard walnut-like tubers DEEP in the ground (6 inches to 2 feet deep).  The tubers can grow as big as large-sized sweet potatoes.  The underground root system can run for yards away from the original tuber and form more tubers and more vines at several node points on the roots.  I have found underground runners over 15 feet long, and they can sprout from anywhere along their length.  If you cut them to the ground, they seem to just shoot back up overnight, from either the same bulb or from adjacent bulbs. Unfortunately, because Smilax is such a fast grower (it can grow over a foot per week), you just can’t sit back and let it take over.  If left for very long, you could be pulling a 30 foot vine down from your trees (risking thorny vine stabs to your face and eyes as the mass falls down on top of you!).
  
    Control of your Smilax problem should focus on early detection and control before more bulbs are formed.   For this reason, I have found that it is more effective to dig up Smilax rather than try to pull it up or cut it down.  This is not a fun job.  With a sharp shovel and many hours of backbreaking sweaty labor, you should be able to get to the hideous roots and tubers buried far below the ground.  These tubers have thorny “knuckles” that look rather like medieval battle maces (those spiked balls on chains).  Be sure you burn or destroy those after you pull them out, as they will just start another shoot if you toss them aside onto the ground.  Try to get all the bulbs out of the ground.  This can be nearly impossible sometimes because the tubers seem to have an affinity for nestling in the roots of woody plants and trees.  I have found them inextricably tangled up in the roots of my oleanders (as well as wrapped around Katrina junk, house bricks and metal debris that I discovered buried far underground).  

    Smilax can be annihilated more efficiently if, in combination with your wanton digging and destruction, you also apply a weedkiller such as Roundup Poison Ivy plus Heavy Brush Killer (or any product that contains triclopyr as well as glyphosate).  Wherever you cut a vine off, spray or brush the cut stem with the weedkiller.  Likewise, if you reach a thick underground root that is buried too deep for you to dig up, cut it or break it off wherever you can get to it, and then paint the cut part with the weedkiller.    If the runners are coming under or over a fence, ask your neighbors if you can go over to their property and dig up the roots and tubers on their side of the fence (they just may thank you profusely!)

    Through some on-line research and discussions with other long-suffering Smilax combatants on the Coast, I’ve learned that people have tried various herbicidal techniques in battling Smilax, including:

    •    Use concentrated glyphosate (at least a 41% or greater active ingredient glyphosate) to paint the cut stems;

    •    Use just triclopyr to paint the cut stems;

    •    Rather than cutting the stems, remove as little of the vine as possible, trying not to break any of the stems.  Find the longest sticker vines in your yard, then lay the vines on some bare ground or on a piece of plastic, and spray or sponge-apply a 10% solution of glyphosate/Roundup, allowing allow the herbicide to stay on the plant for 48 hours.  Then cut the stems back to ground level, and keep re-poisoning any new shoots when they get about 8 inches high;

    •    Or, mix up a few gallons of diluted Roundup solution in a large plastic bucket, then find the longest sticker vines and drape as much of them as you can into the bucket.  Let the vines soak in the solution for a day so that the vines soak up the maximum amount of poison. Then cut the stems back to ground level, and keep re-poisoning any new shoots when they get about 8 inches high;

    •    Or – same general concept here – wrap plastic bags with rubber bands around the sticker vines, filled with Roundup.  Maybe soak some paper towels with Round up and smother the vines with these inside the plastic?  

    •    We welcome more suggestions!  Please submit to the Fourth Ward Cleaver any comments, tips, or suggestions that have worked for you!

    Don’t forget to dispose of any surplus pesticide properly, either by spraying on other weeds, or burying in the dirt where there are no plants growing nearby (apparently, Roundup is inactivated when it makes contact with soil).  I’ve read that frequent applications of herbicide to Smilax will eventually deplete the root mass, though the process may take months, even years. 
     
    So, go ahead and dig, spray, pull, paint, cut, chop, whack, and swear to your heart’s content.  Like a game of “whack-a-mole,” the new vines may continue popping up for a very long time, but, with persistence, you can keep them under control and gradually deplete their energy.  Eventually, your yard could become a happy Smilax-free zone.  

    But if nuclear bombs ever rain on the Gulf Coast someday, destroying most of the human, plant and animal life here – any hardy surviving cockroaches may be discovered by future generations crawling up impenetrable thickets of Smilax cowvines.  

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