Gardening Articles: Flowers :: Perennials

Blue Star (page 2 of 4)

by Rick Darke

Stars for the Garden: Our Top Choices

Though ideal for growing in pots and showy enough to be used as accents, many species are at their best in sweeps and masses. Until recently, only eastern blue star has been widely grown and available in this country, but renewed interest in our floral heritage is bringing out many new choices. The following are among our favorites.

Eastern blue star (A. tabernaemontana) is native to moist, partly sunny habitats in the eastern states. It is hardy to zone 3. Mature plants form upright mounds to 3 feet tall and across. It performs well in soils from arid sands to heavy clays, but it does best in moderately organic soils with average moisture. It withstands full sun but is also at home in light or partial shade, so it can be an effective addition to a deciduous woodland garden. Bloom period varies from late April to late June, depending upon individual seedlings. Some plants have a light, sweet fragrance.

Though the foliage reliably turns a pleasing light yellow in autumn, leaf width and foliage texture vary considerably causing botanists and horticulturists to disagree on whether this species should be divided into varieties. Leaves are typically 3 to 4 inches long and up to 1 inch wide.

Willow blue star (A. t. salicifolia, sometimes listed as A. salicifolia) is much like eastern blue star except its leaves are narrower, longer, and more tapered, giving a willowlike appearance. It blooms in late spring or early summer.

Dwarf blue star (A. montana) grows to 2 feet tall, with smaller leaves. Botanists don't recognize this species, but gardeners will find it listed for sale under this name. Dwarf blue star is probably best considered a horticultural variety of eastern blue star; however, its smaller stature makes this plant distinctive and valuable in the garden.

Threadleaf blue star (A. hubrichtii, sometimes misspelled as A. hubrectii or A. hubrictii), though little known, is the species we would choose above all others. This exceptional plant, native only to Arkansas and Oklahoma, was discovered in 1942 by Leslie Hubricht and named in his honor. Its threadlike leaves, less than 1/16 inch wide and up to 3 inches long, are numerous and closely spaced along the 2- to 3-foot-tall stems. Mature plants have more than 50 stems, forming a spreading billowy mass up to 4 feet wide.

For two to three weeks in May, multitudes of sky blue blossoms top the stems. Summer foliage is a rich medium green. Peak season for this species is autumn, when the stems and leaves turn a vibrant gold that lasts almost through October and November in my zone 6 Pennsylvania garden. By December, the leaves turn a dark honey brown and begin to drop. Late winter is the only time this plant is not showy.

Both Melinda and I place a premium on plants that thrive in our climate and soil (well-drained, unfertilized loam). We've gradually reduced the size of the lawn and replaced it with mixed borders of trees, shrubs, and perennials. Six years ago, we began a new border and chose threadleaf blue star as a medium-height ground cover, to be mixed with hyssop-leaved thoroughwort (Eupatorium hyssopifolium), Sedum 'Matrona', and Viburnum nudum 'Winterthur'. We planted over 100 threadleaf blue stars as year-old seedlings with only one or two stems each, spaced about 2 feet apart.

Today, each plant has 50 or more stems, and the planting forms a dramatic sweep of color, especially in autumn when it is a river of gold flowing around the burgundy tones of the sedum and viburnum. Our only maintenance chore is to cut the stems back annually, which we do in late February or March. Some garden references recommend partial shearing after bloom to reduce plant size and create a tighter, less billowy mass. We prefer the more natural appearance of unsheared plants. Through experimentation, we've learned that threadleaf blue star's fall color is most pronounced when it's planted in full sun. The plants also do well in as much as half a day of shade.

Threadleaf blue star has proved hardy to zone 4, yet is unfazed by the summer extremes of the southern states. In our garden, prolonged summer droughts are a challenge, yet our plantings have required virtually no supplemental watering to thrive. This species is adapted to a wide range of soils from sands to clays, and seems capable of thriving in both acidic and alkaline conditions.

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