ANNA, Ill. — Native plants make or break food webs.
“About 90% of insect larvae are only going to eat plants which they have co-evolved,” said Erin Garrett, University of Illinois Extension energy and environmental stewardship educator serving Alexander, Johnson, Massac, Pulaski and Union counties.
“Insects are the next level of the food web above plants and they do a lot of hard work turning not so easy to digest plant material into much more easily digestible bites of food which is themselves for birds and amphibians to gobble up,” said Garrett during a webinar hosted by the U of I Extension.
However, Garrett said, not all native plants are created equal.
“Only about 5% of our native plants will provide 75% of the caterpillar food,” she said.
Research shows that woody plants like trees and shrubs support the highest diversity of caterpillars, Garrett said.
“Oaks can support over 500 species of caterpillars across North America,” Garrett said.
“One of the most important roles of plants in a shade garden is they provide a safe haven for caterpillars to pupate under trees, so caterpillars are going to drop from trees and rely on leaf litter or ground cover to complete their lifecycle,” she said. “A lawn is not the safest place for them to do that, but native plants under trees provide undisturbed habitat for caterpillars.”
For the ecological goal of gardens, not only do native plants provide habitat for insects, birds or wildlife, as well as food, the garden can also aid in water filtration.
“And some plants are really great at storing nutrients and releasing them later in the year,” Garrett said. “It’s not just about the direct impact. It’s also about providing good habitat and building up the ecosystem services.”
Garrett encourages gardeners to create gardens that mimic what they see in nature, with different layers of plants structured around each other.
The three categories include structural plants such as trees and shrubs, ground cover plantings with sedges, ferns and grasses and seasonal plants which include wildflowers and ephemerals.
Native plants can be planted by seeds, bare roots or plugs.
“Seeds are the least expensive and least reliable way to start native plants because many species are difficult to start from seed,” Garrett said. “Bare roots and plugs are a much faster way to start a garden.”
Plants will thrive in different amounts of shade. Light shade is an area that receives three to five hours of direct sunlight in the summertime, partial shade is two hours of direct sun or shaded for more than half a day and full shade is less than one hour of direct sun.
Garrett identified several plants for gardeners to consider in their shade gardens starting with structural plants.
“Redbud is a small tree that grows 12 to 30 feet tall and is a very popular landscape tree because of the flowers that emerge in the spring,” she said. “The flowers are followed with heart-shaped leaves and seed pods that support 22 species of caterpillars.”
Flowering dogwood does well in partial shade to full sun and the flowers are replaced by green foliage.
“The leaves have a pointed tip and it is very stunning foliage that supports over 100 species of caterpillars,” Garrett said.
Serviceberry does well on loam, sandy or rocky soils and it will flower before it puts out leaves.
“This tree supports 91 species of caterpillars and the fruit is eaten by birds including the Baltimore oriole,” Garrett said.
For shrubs, Garrett said, spicebush grows 6 to 8 feet tall and is not preferred by deer.
“It has beautiful yellow flowers, the leaves turn yellow in the fall and it produces bright red berries,” she said.
Winterberry holly is a popular landscape plant and there are separate male and female plants.
“Buy at least two of them so you will have the chance of having berries,” Garrett aid. “This shrub supports 41 species of caterpillars and it is pollinated by bees.”
Since seasonal plants die back to the ground in the summertime, Garrett said, gardeners should intersperse them with groundcover plants and other wildflowers that retain their foliage throughout the season.
“Spring beauty is one of the first ephemerals to start blooming and they prefer light to full shade, but I have them growing in my lawn in full sun,” she said. “The foliage will die back by the middle of summer, but they are a really important source of food for early foraging insects.”
The blooming window is short for bloodroot. The flowers of this plant emerge with a small leaf wrapped underneath the flower and after the flower blooms the leaves continue to grow and can get to at least 6 inches across.
“Bloodroot is deer resistant because it has toxic, reddish juice inside the stems and roots,” Garrett said. “The seeds have an oil body on them that is very nutritious and delicious for ants so they eat the oil body and discard the seeds which plants the Bloodroot in a new spot.”
White and yellow trout lily plants spread overtime to form colonies; however, patience is required.
“It takes a minimum of seven years for them to mature enough to flower,” Garrett said. “They are mature enough to flower when they develop two leaves.”
The wildflower blue cohosh produces unique green flowers that will be replaced by blue berries.
“The berries are not edible to humans, but birds will eat them and spread the seeds,” Garrett said.
Blue-stemmed goldenrod has arching stems and clusters of flowers. These plants prefer partial to full sun and they will bloom from August to October.
“They are deer resistant and can support 112 species of caterpillars,” Garrett said. “The plants are visited by wasps and flies, as well, and the seeds can be eaten by some birds.”
Solomon’s seal can grow in any light from full sun to full shade and it arches to the side with flowers that dangle under the arched leaves.
“This plant spreads to form colonies and the leaves will turn a golden color in the fall,” Garrett said.
“If you’re looking for an alternative to hostas, ferns are a great choice,” she said. “The Christmas fern is one of my favorites because it stays green year around and it is deer resistant.”
Gardeners often overlook sedges which are a really great option for ground cover.
“There are a huge number of different sedges available,” Garrett said. “Pennsylvania sedge does well in drier soil and it can spread 3 to 8 inches per year so it can be divided.”
When gardeners add native plants, Garrett said, it does not mean they have to rip out all the plants they currently have growing.
“You can make an impact and provide ecosystem services and habitat by retaining some of your existing plants and adding natives,” she said.