Why choose native plants?
Is it because they belong in the Lowcountry? Azaleas and crape myrtles look like they belong and they’re not native. Is it because they’re not bothered by insects and disease? That’s totally not true. Is it because they’re beautiful? So is Chinese wisteria and it’s not native. In fact, it’s invasive.
Invasive plants may look harmless, even beautiful, but they can alter an ecosystem. Some invasives have been purposely introduced because they are fast-growing and pest-free, and that’s precisely why they’ve become a problem. Not all plants introduced from another continent, referred to as exotics, are invasive. But they’re not native.
What exactly is a native plant? The answer is nebulous. You could say that it’s a plant that’s been growing here a long time. Some people suggest it’s a plant that’s been growing here at least 500 years. That would be about the time Columbus sailed the ocean blue. It also would be enough time for plants to adapt to the climate and, just as importantly, allow other organisms to adapt to its presence.
Still, why choose a native plant? It was Douglas W. Tallamy’s book, "Bringing Nature Home," that convinced me why it’s important. Native plants are not immune to insects and disease; that fact, among others, is what makes native plants so valuable.
All plants, native and exotic, are the first trophic level in our ecosystem. They capture sunlight and convert it into chemical energy in the form of carbohydrates, sugars and starches. In order to pass this energy up the food chain, plants are consumed by herbaceous organisms. Insects are a critical link in this energy transfer. Pound for pound, they contain more protein than beef. As insects consume foliage, they are eaten by birds and other organisms. When we only have pest-free plants, those that don’t get consumed by insects, then a vast majority of the sun’s converted energy stays locked on the first trophic level.
Plants produce chemical compounds to ward off insects. The majority of insects are specialists that feed on a few hosts by producing digestive enzymes to break down certain plant toxins. However, the evolution of this ability takes more than a weekend, or even a few months to develop. It could be 500 years or longer.
Even noninvasive exotic plants are less likely to feed as many insects as natives. They will utilize sunlight, water and nutrients but limit the amount of energy shared with the rest of the ecosystem by hosting fewer insects. Consider this effect on birds. While birds eat berries, they rely almost exclusively on earthworms, caterpillars and various insects to feed their young. This highlights the importance of insect availability to birds during nesting and the presence of native plants in our landscape.
The bigger picture is native plants’ impact on biodiversity. The more organisms supported by an ecosystem’s flora, the more stable it becomes.
The South Carolina Native Plant Society supports the cultivation and use of native plants through plant sales and education. The SCNPS Lowcountry Chapter offers grants for school and community projects to facilitate its mission. The Trident Technical College Horticulture Program was the recipient of one of last year’s grants. Horticulture students used the funds to launch a floating wetland in a retaining pond on Thornley Campus.
Buoyant panels and native aquatic plants were acquired from Charleston Aquatics on Johns Island. Roots dangle in the water to absorb pollutants and excess nutrients that contribute to algal blooms. The floating wetland also supports pollinators and other wildlife.