In the Garden:
Upper South
April, 2008
Regional Report

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Sedums are among the plants being evaluated at the Chicago Botanic Garden.

Choosing The Best

It's a very dangerous time of year. Maybe not for everyone, but it certainly is for me. Just going to the grocery can get me into trouble. The discount department and home building supply stores make me break out in a cold sweat. And an actual garden center, well, that's just beyond the pale. No matter how good my intentions to cut back on the number of new plants, they just seem to jump into my shopping cart all on their own.

Who could resist that tempting 'White Star' lithodora? Not that I knew what a lithodora was, but it certainly had gorgeous flowers. And, oh, how lovely, the fragrance of those various dianthus. How to choose among them? Bring them all home.

Of course, one of the logical ways to short-circuit this phenomena, at least until there's a Plant Shoppers Anonymous, is to have a plan, to know precisely what is needed for the garden and to know the most excellent varieties. When I am of sane and rational mind, one of my favorite places to start learning about the best possibilities is to look at the plants chosen by the Chicago Botanic Garden's Plant Evaluation Program.

Scientific Comparisons
The goal of the Plant Evaluation Program is to determine, through scientific evaluation, which plants are superior for gardens in the upper Midwest. While this is a zone or two colder than our region, I feel that their recommendations are very applicable to the Upper South region, even with climate change. Plants are rated on ornamental qualities, cultural adaptability, winter hardiness, and disease and pest resistance. The plants included in the evaluations are, for the most part, readily available in garden centers. (If you can't find them locally, use Plant Information Online (http://plantinfo.umn.edu/).

In the Plant Evaluation Program, perennials are evaluated for four years, while shrubs and vines go through 6 years of comparisons and 7 to 10 years for trees. Information on the top-performing plants are available as Plant Evaluation Notes in PDF format on their Web site (http://www.chicagobotanic.org/research/plant_evaluation/index.php). Because of the thorough and rigorous testing, only thirty evaluations are presently available, but these represent some of the better choices for gardens (and thirty more plants are under evaluation).

What I particularly like about these evaluations is they help me understand the pluses and minuses of the different varieties or species, their growing requirements, and how to best use them in the garden. What is also useful about the Evaluation Notes is that they not only provide information about the best varieties, but they also give detailed growing information. The major downside is the continual introduction of new cultivars, but by studying the Notes, it's easier to make good buying decisions.

A Few Highlights
The most recently released evaluation was of that beloved garden perennial, the Shasta daisy (Leucanthemum x superbum), with 'Amelia' and 'Becky' selected as the most outstanding cultivars. The report points out that although Shasta daisies are often short-lived perennials, these two varieties were consistently healthy with heavy flower production and robust growth throughout the evaluation period.

Catmints (Nepeta) are among the most handsome and dependable of garden perennials, bearing a profusion of lavender to purple flowers over a long period in summer. Altogether 22 of the 30 catmints were rated highly for heavy flower production, robust growth, and winter hardiness. 'Walker's Low', 'Joanna Reed', 'Six Hills Giant', and 'Select Blue' took top honors.

Contrary to popular opinion, goldenrod pollen is not the culprit for fall hay fever. That distinction goes to ragweed. So it's quite safe to use goldenrods in the garden, and they provide a long period of bright color in late summer. The Plant Evaluation Notes for goldenrod are quite helpful in describing the various species and cultivars and where in the garden they are best suited. Among the best are 'Baby Sun', 'Goldkind', 'Fireworks', and 'Golden Fleece'.

Whether or not plants jump into your shopping cart unbidden, reading about growing requirements and varieties, such as the Plant Evaluation Notes, before purchasing will increase your chances of success and save time and money.


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