Charleston is blessed with an abundant garden season – effectively twelve full months of at least something that is thriving in the gardens. My green thumb clients from northern climates are often blown away with this unfamiliar paradigm – yes, you’ll find yourself trimming and fertilizing something or another in every month.
Our subtropical climate also presents its challenges. Non-native invasive plants have taken up residence across our landscape and have proven to be very difficult to control in many cases. Perhaps the most infamous example is the ubiquitous kudzu vine, which blankets and smothers trees, buildings – anything – that finds itself in its path, earning the appropriate nickname “the vine that ate the South.”
While kudzu may be considered a worst-case scenario, there are other invasive plants that afflict the home gardener which should be controlled, and often eliminated.
I will go so far as to say that if you find any of these species in a nursery or garden shop, that you actually consider shopping elsewhere or, at least, have a polite conversation with the garden manager about the deleterious effects of exposing these plants to the open environment.
To the casual observer, few spring-blooming plants are more beautiful or fragrant in the southern spring garden than Wisteria. Just in time for the March and April garden tours, Wisteria begins to bloom a stunning show of lilac-purple flowers in profuse bunches.
With an appearance reminiscent of grapes and a marvelous fragrance, Wisteria makes for a showstopper in the Charleston garden, and in fact many homeowners boast a magnificent display on a garden wall, trellis, or even as a shrub.
But make no mistake: controlling Wisteria is no small chore and, unless you know what you’re getting in to, can be a nightmare.
Left unchecked, Wisteria of the Chinese (Wisteria sinensis) and Japanese (Wisteria floribunda) species will inflict havoc – their woody vines growing incredibly fast, attaching themselves to anything and everything, rapidly extending to seemingly any height. They will pull down fences, smother shrubs, collapse entire trees, even latch on to and damage your home.
This aggressively invasive plant in the wild has proven to be especially problematic, its thick vines curling around native shrubs and trees, blanketing everything in a thick canopy of leaves. Existing plants invaded by Wisteria are often killed in the process, destroying habitats for native animal species.
May the odds be ever in your favor, as this is going to take time, muscle, and chemicals.
The base of these vines can be huge and in the worst cases have completely inundated tall trees.
You must pull the vines out of the trees and shrubs – I recommend starting by killing the vine first since it becomes more brittle once dried out.
Completely cut through the base of the vine with shears or a saw, and immediately paint the stub with the strongest systemic herbicide you can find (like concentrated glyphosate – wear protective equipment). If you are adverse to using such herbicides just know that the vine will absolutely grow back, stronger than ever – but with years of persistence you may eventually succeed in starving the root system. Best of luck.
Native Alternatives to Wisteria
There is a species of Wisteria native to the wetlands of the southeast United States – American Wisteria (Wisteria frutescens) – that has a similar appearance to its cousins but is not quite as aggressive. This Wisteria tends to form shrubs or even small trees, although it can still be a fast climbing vine – just not nearly to the extent of sinensis or floribunda. Its flower bunches are smaller than those of its Asian cousins, and blooms in summer rather than spring, showing its lovely flowers in June and July.
Other native blooming vines to consider:
- Carolina Jessamine (Gelsemium sempervirens)
- Coral Honeysuckle (Lonicera sempervirens)
- Crossvine (Bignonia capreolata)
- Trumpet Creeper (Campsis radicans)
- Star Jasmine (Trachelospermum jasminoides)
Perhaps my personal most hated plant, the Bradford Pear Tree has been a favorite of home builders, corporate landscapers, city streetscapers, and the unsuspecting homeowner.
Cultivated in the 1960s, the Bradford cultivar of the Pear Tree (Pyrus calleryana ‘Bradford’) was marveled as the perfect ornamental tree, growing to a handsome shape with a flush of lovely white blooms in early spring.
However, the marvels of science are not always positive.
The love affair with the Bradford Pear becomes quite soured for those tasked with caring for them – rather than flourishing for decades like similar ornamental trees, they have proven to exhibit a remarkably weak branch structure, with limbs succumbing to severe, sometimes fatal, damage from even mild to moderate storms.
Featured in strip malls and parking lots across the United States, they often fail after only 15 to 20 years, much less than their native counterparts. They fare no better in the yards of homes in Charleston.
The worst offense of the Bradford Pear, though, is due to its genetics. It was cultivated by the Department of Agriculture to be sterile – so, controllable – but that is not at all how the story panned out.
By the late 1990s, Bradford Pear trees began to bear fruit, spreading like wildfire into forests. Worse still, the Bradford Pear in bloom will cross-pollinate with every other cultivar of the Pyrus calleryana species in the wild, creating Frankenstein hybrids that in turn invade the landscape and crowd out native trees. It’s been deemed the kudzu of trees.
Controlling Bradford Pear
There is only one solution, and you will have the full support of the S.C. Forestry Commission in doing so: cut them down, every last one.
Native Alternatives to Bradford Pear
- Flowering Dogwood (Cornus florida)
- Eastern Redbud (Cercis canadensis)
- Red Maple (Acer rubrum)
- Hawthorn (Crataegus spp.)
- Fringetree (Chionanthus virginicus)
Yes, the handsome ivy leaves found everywhere from bouquets to ground covers is in fact an invasive non-native that will crawl onto anything. Still widely available in garden shops, English Ivy (Hedera helix) will not only take over that garden bed, its vines will climb trees and structures and choke other plants of sunlight, eventually destroying them.
The woody vines embed themselves into tree trunks and are very difficult to remove completely, often leaving scars in the tree bark. The vine is equally happy to grow into the mortar of brickwork, and absolutely causes damage to your home in the process.
Adding insult to injury, English Ivy is known to harbor bacterial leaf scorch (Xylella fastidiosa), a plant pathogen which afflicts a number of our precious native trees including oaks, maples, and elms.
Controlling English Ivy
Pull it out. Uproot the vine when the soil is moist, and be sure to get all of it – this may require multiple visits. Eliminating English Ivy from trees is more difficult; you can tear the vines from the tree bark, but only to the height you can access – anything above that is just going to stay there until it eventually loosens, often hanging loose for years until someone with Tarzan skills shows up to finish the job.
If the infestation is extensive, bring out the big guns – cut what you can and paint the remaining vegetative portions with a systemic herbicide (like concentrated glyphosate – wear protective equipment).
Native Alternatives to English Ivy
- Virginia Creeper (Parthenocissus quinquefolia)
- Wild Ginger (Asarum canadense)
- Allegheny Spurge (Pachysandra procumbens)
- Galax (Galax aphylla)
- Green and Gold (Chrysogonum virginianum)
Invasive Plants Booklet from Clemson Cooperative Extension
Native Plant Alternatives from South Carolina Native Plant Society