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 friends 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 – often relegated to roadsides rather than gardens – 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 our Lowcountry.
Let’s take a look at the worst offenders.
Wisteria
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 marvelously sweet 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: Wisteria is an aggressive species and controlling it is no small chore.
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.
Existing plants invaded by Wisteria are often smothered in the process, destroying habitats for many native plant and animal species.
Controlling Wisteria
May the odds be ever in your favor, as this is going to take time, muscle, and ultimately some unpleasant 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 are comfortable with.
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, but invasive Wisteria must be eliminated.
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 later in summer rather than spring, showing its lovely flowers in June and July.
Other native blooming vines to consider:
- Carolina Jessamine * (Gelsemium sempervirens)
* The state flower of South Carolina - Coral Honeysuckle (Lonicera sempervirens)
- Cross-Vine (Bignonia capreolata)
- American Wisteria (Wisteria frutescens)
- Confederate Jasmine (Trachelospermum jasminoides)
(very common but not native)
Bradford Pear Tree
The Bradford Pear Tree has long been a favorite of landscapers, home builders, and urban arborists since its cultivation in the 1960s by scientists at the US Department of Agriculture.
Marveled as an ideal ornamental tree, the Bradford cultivar matures into a handsome lollipop appearance of medium height, perfect for street trees. With a flush of lovely white blooms in early spring and vibrantly colored leaves in the autumn, the easy-to-grow Bradford Pear spread like wildfire in neighborhoods and along sidewalks across the United States.
After three decades of success, the love affair with the Bradford Pear by the 1990s began to sour into an ecological catastrophe. This non-native cultivar was intended to be sterile so as to be controllable, however the grafting process produced viable seeds and also cross-pollination with other invasive varieties Pyrus calleryana in the wild.
The resulting thickets of thorny, rapidly growing, smelly hybrids have displaced countless native plants and must be mowed down every year.
A further disappointment came for those tasked with caring for these trees – rather than flourishing for decades like similar ornamental trees, they have proven to exhibit a remarkably weak branch structure. During even mild storms the branches of the Bradford Pear can succumb to severe damage from splitting.
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. As such, the Bradford Pear has been deemed the kudzu of trees.
Controlling the Bradford Pear Tree
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.
Clemson University offers a Bradford Pear Bounty in which you can cut down the invasive specimens in exchange for up to five native young trees.
Update 2021: Beginning in 2024, the sale of Bradford Pear Trees will be illegal in the State of South Carolina.
Alternatives to Bradford Pear Tree
I love white flowers on spring blooming trees, and there are plenty of alternatives to Bradford Pear – many that are also native to South Carolina:
Other native blooming vines to consider:
- Flowering Dogwood (Lonicera sempervirens)
- Eastern Redbud (Cercis canadensis)
- Red Maple (Acer rubrum)
- Hawthorn (Crataegus spp.)
- American Fringe Tree (Chionanthus virginicus)
English Ivy
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)
Excellent Resources
Invasive Plants Booklet from Clemson Cooperative Extension
Native Plant Alternatives from South Carolina Native Plant Society