If you are struggling to grow lawn under the shade of trees, then maybe it’s time to unleash a patch of woodland wildflowers.
Virginia bluebell, wood poppy, Jacob’s ladder, wild geranium, woolen britches, yellow violet, wild sweet William, roundleaf groundsel and columbine are all spring-blooming species that work well naturalized beneath the high branches of oak, sweet gum or black walnut trees.
Because many spring wildflowers go dormant by summer, mix in sensitive fern, Maidenhair fern or Ostrich fern to fill in gaps that appear midseason and provide structure. Shrubs, including smooth hydrangea, beautyberry and shrubby St. John’s wort are all shade tolerant and help provide year-round structure.
Summer and fall bloomers round out the season. They include purple coneflower, star coreopsis, downy skullcap, showy goldenrod, Ohio horsemint, sweet coneflower, American bellflower and eastern blazing star.
Don’t forget grasses and sedges. I recommend starting with a few woodland rye, bottlebrush grass, American beakgrain or river oats. Sedges such as palm, oak, star, Pennsylvania and cattail add a fine-textured contrast to the wildflowers. Remember that in nature, grasses and flowers are randomly mixed like a tossed salad. This approach will look terrific beneath the trees in your yard as well.
Prepping the area
Start your project in March by killing an area of turf grass about 200 square feet. If you are ambitious, double or triple this amount.
This can be done by pinning down a tarp or a piece of plastic for eight to 10 weeks in the shade of medium (40-plus feet) to large trees (60-plus feet), possibly circling the trunk of one. Then remove the covering, install your plants, lay 2 inches of ground leaf mulch on the bare soil, and water immediately. If it doesn’t rain, water weekly.
Finally, keep the weeds out. Remove lower tree branches to a height of 15 feet for medium trees and 25 feet for large trees to allow indirect side light to enter the garden.
Install plants 18 to 20 inches apart. This way, plants grow in thickly by the following season and work to crowd out some of the weeds.
To calculate the number of plants needed, there is a helpful plant calculator at classygroundcovers.com. Plant in a triangular pattern. For example, if your planting area is 200 square feet, and you are planting 18 inches apart, then you will need 103 plants total. At 20 inches apart, you will need 83 plants. If you are planting on a budget, consider buying plugs or small pots and plant 24 inches apart (58 plants).
The next year in April, look for new seedlings that will begin to appear and spread. You may expand the planting area outward to make it bigger or dig up and move seedlings to create new beds. This is what will unleash woodland wildflowers.
They will spread by themselves, especially if you rake up tree leaves in March so that new seedlings can germinate in April and grow in the bare spaces, unencumbered by a thick layer of leaves.
Don’t forget to trim spent foliage and stems to a height of 8 to 22 inches. Many species of native bees nest in dead stems. New plant growth in April will hide the stubble.
What are you waiting for? It’s time to unleash woodland wildflowers in a shaded space near you. What could be more fun and beneficial to human and wildlife health? Happy gardening!
Woodbury is the curator of the Whitmire Wildflower Garden at Shaw Nature Reserve in Gray Summit, Mo., and an adviser to the Missouri Prairie Foundation’s Grow Native! program.