Garden thugs

By Louisa Cameron

According to the Encyclopedia Britannica, the Thugs were a secret Hindu sect who strangled people and sacrificed to Kali, the goddess of destruction. These murderers traveled in gangs and often preyed on travelers. In the garden a thug is an evil plant that looks good at first and then gangs up and invades with a vengeance. It often strangles, too.

Probably the strongest strangler is the gorgeous and prolific non-native wisteria vine that drips fragrant lavender clusters in early spring. An iconic southern plant introduced from the orient, Wisteria floribunda is wildly aggressive, a superior climber, and strong enough to bring down a fence. One source for buying this variety suggests that it not be planted near the house. There are two native American species: Wisteria frutescens and Wisteria macrostachya. Japanese and Chinese wisterias are the most vigorous and are considered invasive in some states. All parts of the plant are toxic, especially the seed pods, where the toxin is concentrated. The pods do not have a foul odor or taste, so they are particularly dangerous for children and dogs.

Another strangler is the evergreen smilax vine (greenbrier) that grows from giant bulbs with a vague resemblance to a rutabaga or kohlrabi. There are three species native to South Carolina. Smilax glabra does not have thorns and is often used to decorate southern mantels and stair rails at Christmas. All smilax is extremely difficult to eradicate, and we have several among our largest azaleas that have been a nuisance for 40 years. The soft green tendrils are excellent at twining up among the branches of shrubs and trees to the surface that is then rapidly smothered by the smilax leaves. The bulbs are a challenge to dig out from around the roots of their victims and they seem to multiply as if by magic. Many weed killers will not affect them.

Ficus pumilla, or fig vine, is one of the most useful vines for disguising walls and fences, for covering wire topiaries, and for adding a dark green mat where desired. If clipped often, the matte leaves will remain small and dense, but if left to ramble, the vine can strangle trees and ruin stucco. It is an excellent climber with adhesive rootlets. Unpruned, the leaves grow much larger, and a fig-like fruit will often appear. Shoots from the base of the vine will quickly “run” great lengths up structures and across flower beds and anything else in the way. The vine clings viciously, pulling mortar out from between bricks and damaging paint when pulled away. A growth hormone inhibitor (available at nursery supply companies; Possum’s, for instance) can be put to good use. Confederate jasmine is much more manageable and highly fragrant.

I once pinched some cashmere bouquet (Clerodendrum bungei) from a graveyard and paid for my thievery for years. The blossoms were fragrant pale maroon pom-poms, but the plants grew way too tall, spread like wildfire by stolon and seed, and the leaves had a vile odor. I finally got rid of it, along with the fast-spreading chocolate vine (Akebia quinata) that an English visitor had insisted we needed in our garden. I have come to the same conclusion as my mother did: Most vines are problematic in a small garden.

I have been trying unsuccessfully for decades to eliminate the alstroemeria that somehow got added to our thug collection. This pretty plant, also known as the Peruvian lily, has pods that burrow down about ten inches and can hold moisture. Grubbing them out from beneath shrubs is hopeless and they spread by seed and reproduction of the pods. Another thug we added due to ignorance is tetrapanex, the rice paper plant. Its huge star-shaped leaves held high on thick stems lend an exotic texture to groups of plants, but the roots spread rapidly and the pollen is thick, dusty, and highly allergenic.

We inherited a 40-foot grove of clumping bamboo along our western border that must be thinned out regularly. Digging is impossible unless it’s with heavy equipment. But the oldest canes are over 30 feet tall and effectively camouflage a neighboring façade and at least the shoots clump and do not run. One of several plants that can grow and even bloom beneath the bamboo is Eomecon. This relative of poppies and bloodroot is commonly called the snow poppy, but it looks similar to an anemone. It has four crisp white petals around a center yellow ring of stamen held above soft roundish leaves and it grows to a height of about 15 inches. Eomecon tolerates heavy shade although it blooms more prolifically in filtered sunlight. It spreads practically before one’s eyes and needs constant pulling to keep it in bounds, as it sends out many long runners just beneath the surface of the soil.

I naively thought that Cyperus eragrostis, which resembles a short papyrus plant, would be an excellent medium height ground cover for difficult spots. It was, but it quickly covered everything in its path. Much to my chagrin, I found out that I had planted something that was a member of the sedge family. One variety of cyperus has been known to take over entire rice fields. I pulled out most of it but retain it for spots where little else will grow. Its thick root system is effective at preventing other weeds from coming up through its patch, but you must keep a close eye on it. Another ground cover I coveted grew in healthy patches around Colonial Lake. My husband and I were taking a walk around the pond and asked one of the landscape crew working in the beds if we could have a piece. He just smiled and handed me a generous runner which easily survived being plucked and stuffed into my pocket for the next half hour or so. It took over a flower bed and I removed it all except for a small patch which is intended for the bare earth squares beneath the street trees near our house. Its name is Wedelia trilobata, better known as creeping daisy.

Another plant found at Colonial Lake is Ruellia simplex, the Mexican petunia. This purple beauty has slender dark green leaves on sturdy stems. The lavender (sometimes pink) flowers resemble petunia blossoms and form healthy stands of plants that can grow up to about three feet. There are new dwarf varieties that are much better behaved. I used to help my mother pull out masses of Ruellia, along with the weedy but colorful four o’clocks (Mirabilis jalapa) that invaded her gravel driveway.

South Carolina publishes a current list of invasives. These non-native plant species present a significant threat to native plants and animals and cost taxpayers well over $100 billion a year in damage repair and control. As mentioned above, Chinese and Japanese wisterias, the chocolate vine, and a golden bamboo are on the list. I was surprised to find several listed invasives that are readily available at local nurseries and garden centers. English ivy, the mulberry tree, honeysuckle, the Cherokee rose, and nandina were included. We use a good bit of ivy and nandina in our Charleston garden but I will not be giving any of it away! Cypress vine, some of the clerodendrons, palmettos (seeds dropped by birds), and vinca major are also problematic. We have managed to get rid of most of the plants that want to take over our small space, but I’ll bet that many of you know of quite a few more.

Louisa Huger Pringle Cameron is a native Charlestonian married to Price Cameron, a retired plastic surgeon. She is the author of three books on the gardens of Charleston, enjoys duplicate bridge and is a proud grandmother of three.