Garden Tips: Asters star in fall gardens

Marianne Ophardt, WSU Benton County ExtensionOctober 31, 2013 

My birthday is in September, and I like having sapphires as my birthstone, but as a young girl I was disappointed that asters were my official birth flower. To me, they lacked the beauty of roses, carnations or other birth flowers.

I'm happy to say that today's garden asters have changed my feelings. These fall flowering perennials bring color to the fading garden and are great companions to chrysanthemums.

The name aster is derived from the Greek word for "star," which is attributed to the centers of these small daisy-like flowers. In the language of flowers, asters supposedly symbolize love, faith, wisdom and color.

Asters are an easy-to-grow perennial that has few serious insect or disease problems. Like so many perennials, they grow best in full sun with a well-drained, loamy soil.

There are two main types of aster, along with a few minor types. The major types are New England and New York, and they look much the same. Both are winter hardy and native to eastern North America. They are not considered aggressive or invasive.

Depending on the cultivar, New England asters (Aster novae-angliae) tend to be taller, growing from 3 to 6 feet tall. They have thick, hairy stems and leaves. The hairs sometimes irritate the skin of some people. There are cultivars with red, blue-purple, violet, white or pink flowers produced above the leaves in late summer to early fall.

Because of their upright growth and height, stake or provide some type of support, especially considering our windy weather. To avoid staking the taller New England cultivars, pinch them back early in the growing season to encourage branching. Pinched plants will be shorter and bushier.

(Pinching back means using the thumb and forefinger fingernails to pinch off the tips of tender plant shoots. It is done to encourage branching below the shoot ends to make a plant more compact and to encourage more blooms.)

New York asters (Aster novae-belgii) are more popular and a bit shorter. Depending on the cultivar, they grow from 2 to 4 feet tall. Their stems are thinner and without the irritating hairs. Make sure to stake taller cultivars. There are many purple to blue cultivars, but there are also ones in white and pink. They tend to bloom fairly late, often around the end of September. They are sometimes referred to as the "Michaelmas daisy" because the Feast of St. Michael is observed Sept. 29.

While New York asters are generally more popular than the New England ones, there is a notable exception. A real star of the garden is the Purple Dome New England. Purple Dome is a compact, mounded plant that grows 18 inches tall and 36 inches wide. It is a true "purple dome" in the fall, covered with bright purple semi-double flowers.

Once planted, asters don't need much attention other than staking. If they grow well, they may need dividing every couple of years. If so, divide them in the spring.

Problems to watch for include powdery mildew and aphids.

-- Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.

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