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Plant Evaluation

The program evaluates herbaceous and woody plants in comparative trials, ultimately recommending the top performers to gardeners and the horticulture industry. A new trial of sneezeweeds (Helenium spp.) began in 2017, which features 39 species and cultivars that will be evaluated for four years. There are 19 comparative trials currently underway including Andropogon (bluestem), Asclepias (milkweed), Baptisia (false indigo), Chrysanthemum (hardy mum), Coreopsis (tickseed), Filipendula (meadowsweet), Hamamelis (witch hazel), Helenium (sneezeweed), Hibiscus (rose mallow), Hydrangea paniculata (panicle hydrangea), Hydrangea serrata (Japanese hydrangea), Lespedeza (bush clover), Molinia (purple moor grass), Perovskia (Russian age), Persicaria (smartweed), Potentilla (perennial cinquefoil), Salvia (hardy and non-hardy sage), and Schizachyrium (little bluestem). Issue #41 of Plant Evaluation Notes, "A Comparative Evaluation Study of Geum spp.", was published in January. Three reports on plant trials (Baptisia, Hibiscus and Vernonia) will be published in Fine Gardening this year; this collaboration continues to be popular with their readers and has been renewed for 2018.

About the Plant Evaluation Program

Field observation, years of experience, and a passion for plants—all blend together in the Plant Evaluation Program. This program is dedicated to the scientific study of perennials, annuals, vines, shrubs, and trees.

The Plant Evaluation Program, managed by Richard Hawke, is one of the largest and most diverse in the nation. It is also one of the few programs in the United States that formally evaluates perennials. The Plant Evaluation Program received the Award for Program Excellence from the American Public Garden Association in 2008.

Plant Evaluation

"So many plants have a premium price, and if they don't perform as expected, people get disenchanted," said Hawke, the plant evaluation manager. "You'll find what's hot and new in catalogs and magazines, but I'm all about the tried-and-true. We're here to tell the average gardener and the green industry how plants performed in our evaluations."

The goal of the program is to determine, through scientific evaluation, which plants are superior for gardens in the Upper Midwest. Plants are rated on ornamental qualities, cultural adaptability, winter hardiness, and disease and pest resistance. It is the intent of the program to study and recommend plants that are readily available in area nurseries. Study results are published and reported to both the professional industry and the gardening public.

The evaluation studies are conducted over a long-term period:

  • Four years for perennials
  • Six years for shrubs and vines
  • Seven to ten years for trees

"We observe and review them over a long period so we can say with fair certainty how the plant performs for us," Hawke said.

The fun part for Hawke is starting a trial with unfamiliar plants. Hawke is also involved in evaluating the potential for some popular ornamental plants, such as maiden grass (Miscanthus) and smartweed (Persicarial/Polygonum), to be invasive. This is a concern not only for home gardeners, but for forest preserves and other open spaces where invasive plants compete with native plants.

Two gardens at the Chicago Botanic Garden have served as the program’s home. The Lavin Evaluation Garden is a 2.5-acre site with uniform growing conditions, which include full sun and exposure to wind in all directions. The Pullman Evaluation Garden, which is the site of the Garden’s original test garden, was a landscaped garden for evaluating perennials, vines, shrubs, and small trees suitable for partially shaded conditions. (It has been closed to accommodate construction of new, expanded production greenhouses on the Kris Jarantoski Campus.)

Information on top-performing genera that have been previously evaluated in the program is available in Plant Evaluation Notes, available for download below or for order through the Plant Evaluation program. For a list of plants currently under evaluation in the program, click here.

Plant Evaluation Notes

plant evaluation program