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Wednesday, April 1, 2009 06:47 pm

Some ‘tried and true” blue perennials for your garden

Rozanne geranium

It’s time to begin thinking about adding new plants to our gardens. One of my favorite colors is blue. Unfortunately there are only a handful of blue-flowered perennials.

Recently I had the privilege of attending a program given by Richard Hawke, plant evaluation manager at Chicago Botanic Garden. Richard does comparative evaluation of herbaceous perennials to determine the best garden plants for the Upper Midwest and areas with similar climatic conditions. The herbaceous plants under evaluation are grown outdoors in side-by-side trials for a minimum of four years. Plants are monitored regularly to assess their ornamental traits, cultural adaptability to the soil and environmental conditions of the test site, disease and pest problems and winter injury.

Here are a few of the cool blue flower selections that have been found by Chicago Botanic Gardens to be “Tried and True Proven Perennials.” You can take comfort in knowing that these plants should perform great in a central Illinois garden and provide many years of color and interest in the garden.

“Starlite Prairieblues™” false indigo, Batpisia xbicolor ‘Starlite’, has periwinkle blue flowers in mid to late spring. This plant performs best in full sun and grows three to four feet tall and wide. This robust plant is adorned with blue-green leaves during the summer.

“Twilite Prairieblues™” false indigo, Baptisia xvariicolor “Twilite,” has smoky violet flowers in mid-May to mid-June. This back-of-the-garden plant grows four to five feet tall by five feet wide. This full-sun plant has a shrublike habit.

An early season bloomer is lungwort, Pulmanaria. “Diana Clare” produces violet-blue flowers that open rosy pink in mid-April to late May. This partial-shade to full-shade plant grows one foot tall and two feet wide. While many lungwort plants fizzle during the summer, “Diana Clare” leaves retain a sliver green color.

Rozanne geranium, Geranium “Gerwat,” was selected as the 2008 Perennial Plant of the Year. This could be due in part to its long blooming period. Violet-blue flowers begin in early June and continue to October. This full-sun plant grows 18 inches tall and 26 inches wide.

There are several noteworthy catmints, Nepeta racemosa. Yes, catmint, not catnip. Catmint is a full-sun plant that needs a well-drained soil. Many cultivars are adaptable to hot, dry conditions. “Walker’s Low” was selected as the 2007 Perennial Plant of the Year. Plants grow three feet tall and wide and produce clusters of blue flowers from mid-May to late September. Flower clusters can be as long as 12 inches. “Six Hills Giant” is another great full-season bloomer. Lavender blue flowers appear from early June to October on three-feet-tall by four-feet-wide plants. “Blue Ice” is a great dwarf selection growing to only one foot tall by three feet wide. The name may seem a little misleading as this cultivar produces pale lavender to white flowers. Again, another full season of blooms from early May to early September.

“Raydon’s Favorite” aromatic aster, Symphyotrichum oblongifolium “Raydon’s Favorite,” is a good substitute for New England asters. This end-of-season bloomer produces dark lavender blue flowers in September and October. This plant is not only drought tolerant but also powdery mildew resistant. This full-sun plant grows three feet tall by five feet wide. “October Skies” produces a similar plant with medium lavender blue flowers.

Add a little interest to the fall garden with “Carousel” little bluestem, Schizachyrium scoparium “Carousel.” Little bluestem is a native grass. This compact selection grows three feet tall and wide. Performs best in full sun and will tolerate drought conditions. Blue-green leaves with streaks of pink become a mix of cooper, pink and mahogany in the fall.

Results of plant evaluations are posted on Chicago Botanic Garden plant evaluation notes. Visit their Web site at http://www.chicagobotanic.org/research/plant_evaluation/index.php#notes.

This spring, consider adding one of these Tried and True Perennials to your garden.

Jennifer Fishburn is horticulture educator with the Sangamon-Menard Unit of the University of Illinois Extension. Contact her at fishburn@illinois.edu.

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