Photo by Jess Cole.
Trillium struggling to survive in the woods next to invasive Mondo grass and Ardesia that have invaded.
A topic that has come to overwhelm me lately is that of invasive plants. I see every day how they have reshaped my woods, overtaking and choking out my precious spring ephemerals such as trillium, mayapple, wild hydrangea, and jack-n-pulpit. The Chinese privet and tallow trees crowd out young swamp maples and silverbells in all my favorite swamp spots.
I constantly ponder potential solutions, all while trying to avoid getting lost in a spiral of dismay. There are so few avenues to stop the spread of these invasives, and to try to eradicate them is to commit to a laborious, expensive, ever-uphill battle
At what point, then, should we simply embrace invasive plants as part of the landscape? Unfortunately, most of them appear here to stay. Perhaps it is better that I reconsider how I see them. Understanding these plants' growth habits can help us make smarter planting choices and better conceive of how to utilize them to our benefit.
The first step is to be able to identify these problem plants—many of which are still sold in nurseries and considered landscape staples. Though I don’t believe there is much to be done for most of the invasive spread that has already occurred, there is power in where our dollars go, and we don’t need to further contribute to the problem by purchasing more of these troublesome plants.
I'll share some examples here, all of which have had a direct effect on my woods in St. Francisville, as well as on many of the properties I visit during my work. Consider before using your hard-earned cash on a plant that (1) will likely take over your intentional spaces and (2) you can just go dig up from elsewhere for free, likely helping out a friend and ecosystem while you are at it.
If you find yourself in possession of any of these plants, voluntarily or not, here are some things to consider about how they might be managed (or why they should be avoided) in a landscape.
[Read this next: "Beyond Natives—Eight exotics that belong in your garden"]
Nandina
Nandina is one of those old school landscape staples; I often find it in yards thirty-plus years old. Frankly, I cannot understand why—aside from its evergreen nature. Nandina has an odd leggy growth habit, it's incredibly hard to dig up or transfer, and many believe its highly cyanogenic leaves and berries pose a threat to wildlife that consumes them—especially the ravenous cedar waxwings come winter. A vigorous grower and reseeder, nandina can live in sun and shade, making it an apt candidate to escape into undesired spaces. One of the best bumper stickers I have seen proclaims “Gardeners Against Nandina,” across the city of Austin. I concur, on all levels.
Asian Jasmine
Asian jasmine is a wildly fast-spreading evergreen vine, commonly used in Southern Louisiana as a ground cover in shady areas, such as under the canopy of live oaks. This vine established itself in my woods, though it was never planted intentionally, long before I arrived to steward the land. It has not only taken over much of my forest floor, it climbs into the trees, spreading both vertically and horizontally. I should have stock in Ditch Witch for how often we have rented mini skid steers to eliminate Asian jasmine before installing new garden beds.
Like many plants on this list, these vines are only combated via physical removal or chemicals. I don’t believe in pumping chemicals into our natural spaces or gardens, so physical removal is the choice for me. This vine is so prevalent on my fragile, sandy St. Francisville hills that, since it has choked out everything else, I believe that it has made itself my best option for erosion control. Attempting to totally remove it would likely have negative side effects at this point.
At what point, then, should we simply embrace invasive plants as part of the landscape? Unfortunately, most of them appear here to stay. Perhaps it is better that I reconsider how I see them.
Crepe Myrtle
Here is one invasive on my list of nuisance plants that might come as a surprise to many. When I purchased the seven acres I call home, there was hardly any sun for which I could build my needed greenhouse. We ended up removing twelve crepe myrtles in the flattest area to construct the building. Immediately after, and ever since, the felling of those trees, crepe myrtle sprouts emerge from the root systems throughout my yard. My meadow became half crepe myrtle, shooting up through thick commercial greenhouse plastic, across the entire acre of space.
I find the smooth and twisting trunks and branches of these trees to be quite beautiful, so when we cut them down, we saved the best of the cuts in a pile to later make a cottage garden fence. We built that fence directly into the earth, no cement, after the branches had been sitting in a pile for over a year. Fast forward to another year, and an intense tornado totally removed my shady tree canopy, and wouldn’t you know, nearly every crepe myrtle post rooted and sent shoots from both the base and top of the poles. In addition, with all the new sun, crepe myrtles spread to every corner of my woods, vying for the new open space alongside the parasol and tallow tree. Alas, the twelve trees I removed reproduced to at least twenty. It’s a wild and almost comical scenario; you cannot deny their vigor, I suppose.
Though it’s true that these trees’ spring blooms are beautiful, the truth is that crepe myrtles offer virtually no wildlife benefit. Recent research on right-of-way trees in Baton Rouge found crepe myrtles at 40%, making them the most common single species tree in the state capital, followed by the live oak. What a shame to have a tree with little ecological value, as well as many a pest and disease problems, beat out all the more beneficial native trees.
[Read this next: "A Q&A with Rodrigo Diaz, Invasive Species Expert"]
Mondo Grass
This common, evergreen, Asiatic ground cover thrives in full sun or shade. It is fast growing and so damn dense that it seemingly can choke out any other nearby plant attempting germination. I inherited the mondo grass on my property. It intermingles with my sod areas, which is actually quite nice, as it responds well to mowing. But it has been a never-ending battle to remove its spread from my perennial beds and the understory of my woods. If the mondo grass is here to stay, I do suggest its use as an easy sod alternative to be kept at its natural height of up to eight inches, or mowed to the height you so wish.
Ardesia
The queen of invasive plants to Louisiana woods: everyone knows her and environmental groups spend a great amount of time attempting to control her. Ardesia is an extremely fast evergreen groundcover that thrives in shady conditions. The species Ardesia crenata is our top culprit here in South Louisiana, though all ardesias I have seen sold in nurseries I have also seen invade our woods. A common feature of many invasives is their ability to thrive in any local wild space, while staying evergreen. When many of our native plants go into dormancy, these guys and their swiftly spreading foliage shade out any light from above.
Bamboo
I have found few bamboo cultivars that are not invasive. Even “clumping” varieties often spread and choke out other plants with remarkable power.
Many are often surprised to find out we have a couple of native bamboo species here in the Gulf South—these too, historically, having a dense colonizing habit. These ecologically important species have suffered from how significantly our land has been altered. As an exotic invasive, bamboo is indeed set apart by its versatility: the ways one can utilize it as an infinite and cheap resource are endless, including as staking, building materials, cookware, furniture, paper, and even plastic alternatives. When approached with an open mind and resourceful mindset, much good can be done with bamboo.
