If you really want to design a garden for greater plant diversity, there is no better place to focus your efforts than on the herbaceous layer. More so than other layers, the herbaceous layer is made up of more plant species that take up less room than larger trees and shrubs. A diverse garden provides different colors, fragrances, and food at different times of the year, which is pleasing to both gardeners and wildlife alike. So let’s dig a little deeper this week as we discuss the herbaceous layer.
Form and Function. The herbaceous layer is loosely made up of plants that grow anywhere from 8 inches to a few feet; however, plants like joe pye weed can reach heights of up to 6 feet or more. This layer also consists of perennial, biennial, and annual plants that dieback each fall and then return each spring, whether through underground roots or through re-seeding.
This part of the garden is where gardeners can really get creative and have a major impact on wildlife. Because of their generally smaller size, a greater number of plants can be grouped together. Although it may be tempting to plant as many different plant species in one spot, however, remember that it is also important to avoid an unmanageable number of varieties in any one location, particularly if those plants have different growth and maintenance requirements.
For example, black-eyed susans are relatively fast-growing and can be quite aggressive, so you would not pair them with a slow-growing plant such as cardinal flower. In a small bed all to itself or paired with established shrubs or grasses, however, black eyed susan can help to maintain a strong and attractive weed barrier. So although you should practice some restraint, do not be afraid to explore different combinations of planting schemes until you have your design the way you want it.
Perennials for sun. If you are looking for full-sun workhorses that attract pollinators, look for anise hyssop, bee balm, or native mint species. Anise hyssop, with its licorice-scented leaves flower in the dead heat of summer and continue through the fall. Its seeds and leaves may also be used in cooking. Of course, salvias are among some of the finest full sun selections you can find and they tolerate a wide variety of soil conditions. Try ‘Indigo Spires’, ‘Furman’s Red Autumn Sage’, or ‘Amistad’, plus nearly 900 more varietal selections
A member of the milkweed family, butterfly weed hosts up to 5-7 specialist insects at any given time, including the endangered monarch butterfly. Though a magnet for aphids later in the season, beneficial predators and parasites are attracted to these pests and will help control them for a time. Black eyed susan, purple coneflower, and lancleaf coreopsis are all also sturdy plants for full sun areas. Many Hibiscus species also are available that work well in full sun areas that have moist to wet soils.
Perennials for part shade. Coming in at 5-6 feet tall, joe pye weed is a sturdy addition to a garden that has moist to wet soils. Though it will do well in full sun, it does perform best with some afternoon shade. Green and gold is a mounding ground cover that has bright yellow flowers beginning in mid-spring and lasting through the summer and needs moist soils to really thrive. Heucheras are widely available and will look wonderful through the season, even in full shade areas.
Let there be ferns! In my honest opinion, I do not believe any shade garden is complete without ferns. There are many species available that can add drastically different elements to your garden. Christmas fern, for example, is a low-growing evergreen selection that has sleigh-shaped fronds, while Japanese painted fern has light green and purple fronds that add a wispy splash of color in the shade garden. Ostrich fern is a taller species that can reach heights of 3 to 4 feet, or more! Maiden hair fern that has tiny, gingko-shaped fronds.
For more information, visit ces.ncsu.edu where you can submit questions via the ‘Ask an Expert’ link, or contact your local Cooperative Extension center by phone: If you live in Pender County, call 910-259-1238; in New Hanover County, call 910-798-7660; in Brunswick County call 910-253-2610.
Sam Marshall is the horticulture agent with the North Carolina Cooperative Extension in Brunswick County. Contact him at firstname.lastname@example.org.