As August slides toward September, the heat tends to ease up and many gardens improve in appearance. Some plants will put on a second flush of bloom, annuals that faded in the heat perk up, and the fall flowers—especially asters—add rich, bright color.
Because they give the garden a boost at the end of the season, asters are one of the most popular perennials in the Midwest. They are hardy, sun-loving plants that come in a variety of sizes and colors. All have star-shaped flowers that resemble daisies, but are botanically related to sunflowers.
Care is easy. Asters like a sunny site but will grow in part shade, too. They perform best when provided adequate moisture and grown in well-drained soil. A light application of compost or another organic fertilizer in spring will keep them growing well, but you do not want to over-fertilize or asters will get leggy and bloom less. Like their fall-blooming comrades the chrysanthemums, asters will get a bushier shape and bloom more if they are pinched back in early summer.
Most asters grow 2 to 4 feet tall and 36 inches wide, but height varies depending on the variety. Tartarian asters, for example, can grow up to 8 feet tall. Most of the taller varieties benefit from staking, although some gardeners may prefer not to bother, and I’ve always thought a flopping aster, seeming to swoon under the weight of its blooms, adds a dramatic touch to the fall garden.
Among the more widely available varieties, ‘Purple Dome’, a compact, deep purple variety, ‘Alma Potschke’, a taller variety with rose-red flowers, and ‘Hella Lacy’, with its bright lavender petals and yellow center, are reliable and lovely. For dry areas or rock gardens, you could also try heath aster, which has needle-like foliage and smaller flowers. ‘White Snow’ is a white variety and ‘Blue Star’ has pale blue and yellow flowers.
The only drawback to asters is that the stems sometimes turn brown before the flower has bloomed. Giving the plants adequate moisture helps, and if you don’t like the appearance, you can always keep the asters toward the rear of your flower bed so the stems are hidden.