What is a keystone plant? Keystone species have a disproportionately large effect on the abundance and diversity of other species, like insects, in an ecosystem. Without keystone plants, the local food web may fall apart. Keystone plants affect many species of animals, but pollinators and birds are my primary focus.
Insect scientist E. O. Wilson called insects, “the little things that run the world.” They provide many essential ecological roles that make it possible for humans to survive. Pollination of 87 percent of all the plants on the planet is a free service that insects provide. Can you picture a world where insects have been poisoned or habitat destroyed, and 87 percent of the world’s plants are gone? Insects also provide much of the planet’s pest control.
In North America we have driven three species of bumble bees to extinction (there are only 46 species). In Europe one third of grasshoppers, crickets and katydids are facing extinction. Flying insects in Germany have declined by 79 percent since 1989, and 46 species of butterflies and moths have disappeared completely. Globally insect abundance has been reduced by 45 percent since 1974. We can do our small, but important part to alleviate this problem by planting keystone plants in our yards.
Native narrow-leaf sunflowers. Photo by Donna Legare
Native sunflowers, goldenrods, asters, and blueberries are among the best keystone species that support pollinators. There are many species of goldenrod available to plant – wreath, wand, sweet and downy. Wreath goldenrod is even tolerant of shade and grows to only 2 feet with multiple stems – especially useful in the landscape with beautiful sprays of yellow flowers. Native asters on the market include blue wood aster, Elliott’s, Georgia, New England, and silk grass aster. Blueberries can include hybrids with large, sweet berries or the unique natives such as deerberry, highbush, Elliott’s and sparkleberry.
As striking as the October blooming native sunflowers are, be aware that they spread by both seed and runners and can overwhelm an area. In our yard, we try to contain them to the edges of the property so that we have room for other wildflowers. Narrowleaf sunflower does not get as tall as swamp sunflower, which can grow to eight feet. Blossoms are numerous and about two inches across.
The above species are great for specialist pollinators, like the southeastern blueberry bee, but the multitude of generalist pollinators will appreciate them also.
In North America, butterfly and moth caterpillars are the mainstay of most bird diets, especially when rearing their young, according to scientist Doug Tallamy, author of Nature’s Best Hope. Why focus on caterpillars? It is estimated that there are over 14,000 species of caterpillars. There are even more beetles (25,000 species) but caterpillars are easier to catch, soft, high in proteins and fats, juicy and easier for baby birds to swallow.
Photo: This white oak will grow to be a large shade tree and provide abundant insects for birds to eat. Photo by Vanessa Crisler
A family of 4-5 baby chickadees are fed 350-570 caterpillars a day by their parents. Over the nesting period of around sixteen days the parents deliver 6000 to 9000 caterpillars. The parents seldom fly more than 160 feet from the nest, finding these caterpillars primarily in trees.
All trees are not the same when it comes to hosting caterpillars. The best trees are considered the keystone species for bird abundance and diversity. In our region if you only have room for one more tree, let it be an oak. Since live oak, water oak and laurel oak are common here, I suggest planting a white oak or swamp chestnut oak for diversity. Oaks can harbor 390 species of caterpillars in North Florida which you will seldom see, but the birds will find them.
Other keystone species are black cherry (250), Chickasaw, flatwoods or American plum (250), river birch (172) maples (171), hickory (191) and pines (171). There are many others as well. Numbers of caterpillar species hosted for trees are listed by zip code on the National Wildlife Federation’s Plant Finder (see information box).
White oak in its autumn glory along with fringe tree in foreground. Photo by Vanessa Crisler
Shrubs, grasses, wildflowers and even weeds all host caterpillars, but trees are the best. Remember, regardless of what you plant for birds or pollinators, in most cases it should be native. American insects to a huge extent live only on American native plants. Many non-native flowering perennials are useful too because they produce nectar or pollen and are beautiful in the garden; just be sure that they are not invasive. Also, you can work keystone plants in around some of your established non-native plants like azaleas and camellias. The whole landscape does not need to be native.
Generally non-native trees such as crape myrtle, Chinese fringe tree or ginkgo, though pretty and not invasive, support zero to 3 species of caterpillars in North America and take up space that could be used for an American tree. Think of native trees as bird feeders.
Tallamy says if each American homeowner converted half of their yard to productive native plants, it would collectively restore 20 million acres to a semblance of a functioning ecosystem. How big is 20 million acres? It is bigger than thirteen of the country’s largest national parks combined! Tallamy would call it Homegrown National Park. Let us all do our part in providing for pollinators, birds, and healthy ecosystems.
Enjoy the bees and birds in your yard.
Information Box
www.nwf.org/nativeplantfinder - you can type in your zip code and find the keystone species for your area
www.audubon.org/plantsforbirds
www.apalachee.org – click on the Doug Tallamy presentation and then click Restoring the Little Things that Run the World to hear Tallamy explain it all. Also click on the Rob Williams Yard Tour for a local video on how to get started in Tallahassee.