Unless you're "into" gardening, and especially gardening for wildlife and to preserve biodiversity (as opposed to gardening for aesthetics alone), you're probably not aware of the plethora of gardening groups across Facebook and elsewhere. You're also probably not aware of the drama these groups can foster when it comes to discussions of native vs. non-native plants, of cultivars, and of aggressive vs. invasive plants.
All Greek to you? Let's delve into that a little. What do these words mean in the context of gardening for the planet?
Native: Native plants are ones that evolved naturally in an area—for us, that's plants that evolved naturally in North America—before us humans came along and introduced plants we thought were pretty or more hardy from other places. Natives don't require special fertilizers or gallons of extra water because they already evolved to grow in our local soil and weather conditions, and because they coevolved with wildlife, they alone can provide the food and shelter wildlife need. Just like how humans can eat blueberries but not holly berries, many wildlife can only eat the leaves of Butterfly Weed, for example, and not Butterfly Bush.
"Research shows that using native plants is the best way to create a haven for pollinators like native bees and butterflies and even to attract beneficial insects that will help the rest of your garden. Why? Over millennia, native insects and native plants have co-evolved and reached an intricate balance. Many insects can only eat the plants they co-evolved with."
"Conventional landscapes featuring large lawns and showy alien flowers are often sustained with high levels of fossil fuel use, fertilizers, pesticides, and supplemental water."
Non-native: Plants that did not naturally evolve in an area but were introduced, either unwittingly or intentionally, by human interference, e.g., European settlers brought dandelion seeds to North America in the mid-1600s and planted them, after which they spread across the U.S. to become the ubiquitous but cheerful "weed" we know today. Here's a paper in the American Journal of Botany on accidental plant introductions, as well.
Cultivar: Plant varieties that have been selectively bred to have specific characteristics, e.g., to be smaller or shorter than their original counterparts or to have double petals.
Aggressive: Plants that are native to the area but spread aggressively and may displace other native plants in fragile ecosystems. Because they are native, they should not be classified as invasive, but in some cases, gardeners might choose to be cautious about planting a native but aggressive plant species.
Invasive: Plants that are non-native to the area and whose introduction causes or is likely to cause environmental harm by outcompeting and replacing native plants and disrupting food webs. Here is a list of invasive plant species in Maryland.
"Invasive species can change the food web in an ecosystem by destroying or replacing native food sources. The invasive species may provide little to no food value for wildlife. Invasive species can also alter the abundance or diversity of species that are important habitat for native wildlife. Additionally, some invasive species are capable of changing the conditions in an ecosystem, such as changing soil chemistry or the intensity of wildfires."
"To be invasive, a species must adapt to the new area easily. It must reproduce quickly. It must harm property, the economy, or the native plants and animals of the region."
There's probably a perfect way to garden with all straight species natives to preserve biodiversity, but most people don't have the time, resources, energy, knowledge, access to native plants or even desire to be perfect. I myself have a few non-native (but not known to be invasive) plants in my own garden just because I like them.
But it's important to note that while non-native plants aren't evil, they always have the potential to wreak havoc on biodiversity, and many are known to actively do so. Most importantly, a non-native plant is always going to be taking the place of a native plant.
How bad are invasive plants? Just read about Japanese knotweed, which one man cited in his suicide note, or this article about how Heavenly Bamboo kills birds. Check out how an entire state (Delaware) has banned the commercial traffic of invasive plants. These are just a few examples of how important it is for us to prioritize native plants in our landscapes.
"All the birds had intact Nandina berries in their crops. There was hemorrhaging in the heart, lungs, trachea, abdominal cavity and other organs. ... Yet homeowners and commercial landscapers are still planting this toxic species without constraint."
That's why things can get a little dramatic in gardening groups when people talk about plants. And that's what happened when I posted the graphic above, featuring photos of both a Heavenly Bamboo (Nandina domestica) and a Heavenly Bamboo cultivar, Nandina domestica "Gulfstream," as well as four native cultivar suggestions (male and female dwarf Inkberries, dwarf Highbush Blueberry, and dwarf Virginia Sweetspire) as replacements.
What was the drama? Heavenly Bamboo is actively harmful. The smaller Heavenly Bamboo cultivar is perhaps not as actively harmful because it's been cultivated to have no berries, so some thought it shouldn't have been included as "the worst," but we just can't say for sure long-term. In the words of Jurassic Park: Life finds a way. The "berry-less" cultivar has been known to grow berries and is favored by landscaping companies, so I included it as "the worst" along with the larger version of the plant.
What was the secondary drama? I included four native cultivar suggestions that were, in my opinion, closest to the look that people who would typically plant Nandina domestica, especially the smaller cultivar, desire. But planting a pure native (a "straight species") is almost always going to be better for the wildlife who use it than planting a native cultivar. Native straight species are often more attractive to pollinators than their native cultivars. My reasoning is that based on the research, a native cultivar is still better than a non-native anything.
Confused? Basically, native straight species > native cultivar > non-native noninvasive > non-native cultivar of an invasive (cultivated to have the potential be less harmful, e.g., to be sterile so it doesn't spread via seeds) > invasive. Clear as mud!
Because we are pushing up against this confusion, as well as decades of blissful ignorance about just how harmful a seemingly harmless non-native plant can get and big-box stores selling whatever looks good to consumers make a buck ... it's easiest just to try our best, to choose native and native cultivars as often as we can, and to not let perfect be the enemy of good.
Yet there are a few non-native plants—ones that unthinking landscapers plant again and again because they're cheap and available and because consumers don't know the difference—that could be easily swapped with native alternatives. This brings me to our This Plant is the Worst series, which starts with Heavenly Bamboo (Nandina domestica).
Some of the non-native plants I'll feature in the coming months are just "meh." We can consider these plants statues: adding something aesthetically while doing practically nothing to help the environment. Other plants, like Heavenly Bamboo or Butterfly Bush, are genuinely harmful, as in toxic to birds or insects or highly invasive. Each month, I'll target one of these "meh" or "the worst" plants and offer native alternatives that I consider similar in size, function, look and hardiness.