By Jim Affolter, Director of Research at the University of Georgia’s State Botanical Garden
If you visited the Mimsie Lanier Center for Native Plant Studies at the State Botanical Garden of Georgia in Athens two summers ago, you might have come upon the strange sight of a young man waving a leaf-blower in the air with great concentration. The leaf blower was actually working in reverse – acting like a vacuum – sucking up whatever invisible particles were populating the air around these lovely native wildflowers. You might have thought the conservation staff were going to unusual lengths to keep our wildflower displays clean; after all, most gardeners tolerate some dirt and dust on their plants. As it turns out, this wasn’t obsessive-compulsive gardening, it was science.
The young man wielding the leaf-blower was University of Georgia horticulture graduate student JC Poythress, and he wasn’t after dust or pollen, he was collecting insects. For his Master’s thesis, JC was interested in the role that native plants play in supporting healthy and diverse populations of native insects. Abundant and diverse insect populations support more birds, amphibians, and small mammals.
JC designed a field experiment to address the following question: Are native plants typically sold by commercial nurseries and retail outlets (i.e., named varieties representing a single genotype –all plants are genetically identical– like Coreopsis ‘Tequila Sunrise’) equally as effective as local, wild-type plants (as genetically similar as brothers and sisters) in providing food for native herbivorous insects? Are propagated clones of native plants, as opposed to more genetically diverse plants propagated from seed, limiting the ability of these plants to support healthy insect communities in home gardens?
JC’s experiment included five native plant species (grown from seeds he collected in the wild) along with a commercially available cultivar of each of these same species. The cultivars were Amsonia ‘Blue Ice’, Coreopsis ‘Tequila Sunrise,’ Monarda fistulosa ‘Claire Grace,’ Oenothera ‘Cold Crick,’ and Schizachyrium scoparium ‘Prairie Blues.’ During the summer of 2014, he collected insects from the plants in each 2 X 2 square meter plot using a leaf blower that had been modified to act as a vacuum. JC had the unenviable task of tediously separating the tiny insects from the plant material collected on a cloth filter inside the tube of the leaf blower and sorting them for identification.
When he compared the insect communities collected from plants grown from wild-collected seed to those on the corresponding commercial cultivars, JC found that in every case the species composition of the two insect communities was statistically distinct. In other words, certain hemipteran species (including aphids and leafhoppers) predominated on the cultivar while a different assemblage of hemipteran species characterized the plants grown from wild-collected seed. He also demonstrated differences in the total number of insects between seed-propagated species and commercial cultivars, but these differences were not consistently in the same direction; sometimes cultivars had more insects and other times the wild-collected species had more.
Yes, that is a lot of science. What are the practical take-away messages? JC concluded that the best way to encourage diverse and abundant insect populations in your home landscape is to increase the number of different native plant species that you grow, whether they are true species or named varieties. So keep the birds in your neighborhood well fed by adding a diversity of native plant species to your landscape to support a smorgasbord of insects!
Looking to add native plants to your garden? Come to the native plant sale at the State Botanical Garden of Georgia at the University of Georgia October 6, 7, 8, and 13, 14, 15, where we can help you choose from dozens of different plant species. More info at botgarden.uga.edu, firstname.lastname@example.org, or 706-542-1244.