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Live Oak in MacIntosh, FL - Photo Credit: Pam Schmitt
Although most native plants are a valuable addition to the landscape, there is a category of native plants that is most crucial - these are the 'keystones".
A “keystone” is the center part of an arch. Without it, the arch will crumble. Likewise, the food web will fall apart without keystone plants. Putting it together: keystone plants are the native plants that are deemed essential for upholding the food web.
Caterpillars transfer more energy from plants to animals than any other insect. This is why it's important to plant for both the larval and adult stages of pollinators. The caterpillars that don’t turn into butterflies or moths become food for birds (whose populations are sharply declining due in part to a lack of food).
So, will caterpillars destroy all our plants? If your plant is destroyed by feeding caterpillars, that means those caterpillars don’t have a natural predator to keep their population in check. We need to support both native caterpillars and their native predators by growing the keystone plants that are necessary for their continued survival.
The second reason for planting keystone plants is to support pollen specialists. There are some bees that are generalists - they visit a variety of plants and are not picky. But many of our native bees specialize in the flowers they’ll land on. These specialist bees have adapted over time to perfectly pick up the unique pollen granules of their specific plants.
So, planting for generalist bees only benefits them, but planting for specialist bees benefits both them and the generalists. We need both in order to sustain the food web, so adding keystone plants to your pollinator garden will help ensure that specialist bees are not eliminated from the system.
The National Wildlife Federation has developed helpful handouts for each region of the U.S. that identify the keystone plant genera and the number of caterpillar species and pollen specialists that those plants support.
National Wildlife Federation's Keystone Plants by Ecoregion.
For Florida trees, the number one keystone plant genus is Quercus (live oak), since it hosts 395 caterpillar species! Other keystone tree genera are Prunus (black cherry), Acer (red maple), Pinus (slash pine), Ulmus (American elm), and Fraxinus (white ash).
For shrubs, the winning keystone genera is Salix (coastal plain willow), which hosts 190 caterpillar species. Other important keystone genera are Vaccinium (blueberry), Rubus ( blackberry), and Baccharis (saltbush).
Finally, there are several keystone perennials to add to your flower garden. First is Solidago (sweet goldenrod), which hosts 82 caterpillars and supports four pollinator specialists. Other flowering keystone perennials include Helianthus (sunflower), Coreopsis (tickseed), Heterotheca (camphorweed), Rudbeckia (black-eyed Susan), Chrysopsis (Maryland golden-aster), and Verbesina (frostweed).
Look for keystone plants at nurseries that carry native plants. By incorporating some of these plants into your landscape, you can do your part in sustaining our declining insect and bird populations.
Plus, you’ll get to enjoy the beauty of Florida’s native flora.
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