We caught up with local botanist Lisa Calfee one Saturday to learn more about native and invasive plants. We chatted in her backyard, which is overflowing with plant, insect, and animal life, so she could keep an eye on her chickens and the neighborhood’s new predator—a juvenile bald eagle.
We started at the very beginning.
What, exactly, is an invasive plant?
People will refer to an invasive plant as any plant somebody doesn’t want. They use it interchangeably with weed, but that’s not the legal definition. The legal definition has two components: 1) It has to be introduced to a different region of the world than where its historical range was (historical meaning pre-European settlement) and 2) it has to be able to reproduce by itself in the wild.
Here in Nashville, a lot of our invasives are Chinese or European. We’re at the same latitude and the weather, humidity, and soil conditions are quite similar, as indicated by the presence of temperate forests.
What are some of our most notorious invasive plants here in Nashville?
Privet, bush honeysuckle, tree of heaven, empress tree, and Japanese honeysuckle are among the worst ones. Japanese stiltgrass (Microstegium), wintercreeper (Euonymous fortunei), English ivy, and periwinkle are also a problem here. Most of these species were introduced for ornamental purposes. A lot of people want something green in the winter or pretty flowers early in spring, so they imported these plants. Kudzu is also another, very noticeable, invasive plant, especially around Knoxville, Atlanta, and Chattanooga.
Kudzo’s a great example of why invasive plants are such a problem for our ecosystem. They have an unfair advantage in that they have fewer natural predators, so they can spread rapidly. Native plants can’t compete, and we see biodiversity diminish as invasives spread.
I want to point out that just because an introduced plant isn’t bad in 2017 doesn’t mean it won’t be the worst thing in 20 years. It’s a shifting target. So even if it’s not invasive now, that doesn’t mean it won’t be invasive later.
I saw Sarah Stein, author of Noah’s Garden: Restoring the Ecology of Our Own Backyards, speak 25 years ago, and she said it can take 60 to 100 years for a plant to be introduced, become established, and then become invasive, meaning rampant overproduction.
Invasive plant photos are public domain, liscenced under CC0 1.0
Would you draw a distinction, then, between plants that are non-native and plants that are invasive?
I do. Some people don’t. I think it’s much worse to plant a known invasive than it is to plant one that may be a problem in 40 years, but I don’t think you should plant a non-native unless it has very direct human benefits like the tomato or watermelon or some herbs.
Take the Bradford pear for example, a tree introduced for flowers. Bradford pears were widely planted in the 1980’s and 1990’s. All the new subdivisions would plant it because it transplants readily, grows quickly, has good fall color, has pretty flowers, and it doesn’t have the messy fruits that people would get annoyed with. Now, thirty years later, you see it colonizing old fields along the roads. That was unheard of twenty years ago because their fruits were sterile.
Wow. So it can change, and it can change pretty fast.
How did you start learning about invasive plants? What was your introduction to this topic, and why do you care?
I took my first botany course my last semester of college. The course was Field Botany, where we learned basic plant taxonomy. Mid-semester the professor took us to a native plant nursery called Sunlight Gardens outside of Knoxville. Prior to that, I was oblivious to native, introduced, and invasive species, but the owner (Meredith Clebsch) gave a little talk and BAM! I was hooked.
How did that change your educational course, the way you lived your life, and some of your interests?
My undergraduate degree was in zoology. I’ve always loved animals. I’ve always loved the natural world. I’ve always loved plants, but really, animals were my first interest.
That botany class was profound in many ways. I met my husband there, and I found something I was really, really passionate about. I got my first job out of college working for TVA surveying the understory of forests throughout North Carolina.
I was still planning an animal focus for grad school, but my first semester I took a course called Endangered Species Management and Conservation of Biodiversity. It was student-taught, and other students picked topics like the Florida panther and the spotted owl. Those were species I cared about too, but I kept hearing again and again that the problem with every single one of them was habitat. What is habitat? Primarily, plants.
I proposed to the student I was working with that we talk about the importance of plant biodiversity and the protections afforded plants under the Endangered Species Act. Researching for the project made me realize that if I wanted to affect change, I had to start by changing the way people interact with the land. That semester, I jumped ship and moved over to plant sciences. (to be continued)
Be sure to check in next month as we hear more from Lisa about how her passion for native plants and habitat creation has guided how she cares for her West Nashville yard. She’ll also share a few practical tips for removing invasives and restoring habitat in your place.
Lisa Calfee formerly taught botany and biology at Vanderbilt, Queens University, University of North Carolina (Charlotte), and Central Piedmont Community College. Prior to working in academics she worked for Habitat Assessment and Restoration Program and Bartlett Tree Service, both in Charlotte. Upon moving to Nashville, Lisa helped her husband open a small animal veterinary referral and emergency practice. She has a B.S. in Zoology and Biology and a M.S. in Plant Sciences from University of Tennessee, Knoxville. Her Ph.D. is in Horticulture from Virginia Tech. Currently Lisa serves on the Board of Trustees for the Tennessee chapter of the Nature Conservancy and spends most of her time homeschooling her son.