University of Illinois Extension
Planning a new perennial garden? Plant for the whole garden ecosystem

 

[January 26, 2023] 

Welcome to winter. The days are short and cold, and if you enjoy plants, hopefully, you have a few indoors to boost your mood. However, there is already light on the horizon. Spring will be here before you know it, and now is a wonderful time to plan out your new perennial gardens.

The days of planting individual plants and surrounding them in a traditional sea of mulch or rock are numbered. Instead, a design paradigm described in the book “Planting in a Post-Wild World” by Thomas Rainer and Claudia West is one that gardeners are flocking to. The innovative approach incorporates the concept of functional layers that form a complex yet organized landscape that reflects nature.

“We need aesthetically beautiful gardens that perform multiple ecosystem services, and you cannot get that from most traditional landscapes," says Layne Knoche, University of Illinois Extension Outreach Associate and Landscape Designer. "This design method works. We have used it successfully and beautifully at the Red Oak Rain Garden on the campus of University of Illinois in Urbana-Champaign and I have even used it in my own gardens."

Design in Layers

Be aware of layers when designing perennial gardens. Each layer has a selection of plant species that perform a specific function. When designing, it’s best to focus on these three layers: Groundcover, structural, and seasonal.

The groundcover layer

This layer typically consists of low-growing, densely planted grasses, sedges, ferns, and forbs that form a “green mulch” that serves to shade out weeds. Depending on the species chosen, these may be planted in groups of 10 or more and planted as little as 12 inches apart. As they fill in and mature, they protect from soil erosion, provide habitat for overwintering pollinators, and much more.

The structural layer

This layer consists of trees, larger shrubs, tall forbs and grasses, or any other plant that has strong architectural forms. The plants in this layer form the “bones” of the garden that are visible year-round. Individual plants or small groupings – three or five, typically – are appropriate for this layer.

The seasonal layer

This layer features plant species that are visually dominant for a period. These are typically plants with showy blooms or textures. Larger groups and masses of plants in this layer can create stronger visual appeal.

Garden design tips

Keep “right plant, right place” in mind. Know your site’s sun, moisture, and soil conditions, and choose species appropriate for your conditions.
 

Plan for seasonality. Make sure to include some spring ephemerals, summer bloomers, fall color, and winter visual interest.

Order early. Determine the species you want to use as early as possible, especially if you plan on ordering plants from an online nursery. The ship-to-home method has become increasingly popular over the past several years, so the earlier you place your order, the more likely you are to have luck with the species you want.

Designing perennial gardens is a fantastic way to spend a snowy gray day and at University of Illinois Extension, we are here to help. We have a series of guides covering plant selections and planting plans, along with other useful information available at go.illinois.edu/RORGresources.

[Author: Layne Knoche, Visiting Extension Outreach Associate University of Illinois Extension]