Everything You Need to Know to Grow Aster Flowers

Perennial asters are tough, hardy plants that provide beautiful fall color. Asters are easier to grow than mums are and more likely to survive the winter, even when planted in full bloom in the fall. There are many varieties of asters that will suit any sunny garden, from formal to naturalized.

Perennial asters grow around the world, in all kinds of climates, and there are many North American native species. Recently the North American species of aster were reclassified and actually taken out of the aster family. We won't worry about the taxonomic mess here; we will simply refer to them as asters. Aster comes from the Greek word for star, and asters may seem as numerous as stars sparkling across a dry meadow. They are an important source of late-summer and fall food for butterflies and bees.

Native asters are often tall and gangly; they have struggled up through tall grass and weeds to the sunlight. They throw their froth of small, daisylike flowers out above the brush and sprinkle them through the weeds. Cultivated varieties of aster are more compact and have a mounding habit. I happen to like the way the native asters wind their way through other plants and allow the asters in my borders to behave the same way.

Asters have thick, woody stems and long, narrow leaves. Almost all asters are upright plants; there are some that hug the ground and one that is a climbing vine. Aster flowers are small, about an inch across. They come in all shades of blue, purple, white, pink and red. While the centers are often yellow, there are no yellow or orange perennial asters yet. Asters begin blooming in late summer and usually continue blooming until a hard freeze kills them.

Growing asters
There are perennial asters hardy from Zones 3 to 9. Asters tolerate a wide range of soils. They will do well in dry areas but will also do fine in well-watered sites, although they may be more prone to powdery mildew, a fungal disease. Most asters prefer full sun; some will tolerate light shade. Unless your soil is extremely poor, native species of asters do not need fertilization. Some of the cultivated varieties may bloom heavier if they are fertilized in the early spring with a timed-release fertilizer for flowers.

You can start asters from seed but most gardeners will want to start with plants. If you start with seeds, you can sow the seed where you want the plants to grow or, for best results, you can start the seed indoors six to eight weeks before your last frost and transplant outside.

Asters form large clumps and need to be divided every three years or so. Simply dig up the clump in the early spring and separate it into two or three parts, which you will then re plant. Space asters from a foot to three feet apart, depending on variety.

If you want dense, rounded clumps and abundant flowers, pinch your aster plant back by about six inches at the beginning of July. Don't cut back after July 15 though. If you don't pinch back your asters they will be taller and the display will be airy and lighter. In the fall, after a hard freeze has killed the plants, they may be cut off to ground level.

Some people choose to move wild aster plants into the garden. Take only plants from your own property or from areas where you have permission to dig the plants. Individual plants have different growth habits, so choose carefully. It might be best to choose the plant in the fall when it is in bloom, mark the plant, and return in the spring to transplant it, as they seem to establish better when moved in the spring.

Choosing varieties
The native New England Aster has lovely blue-purple flowers. Cultivated varieties of this native include Purple Dome, a deeper purple flower on a rounded, compact plant, and Alma Potschke with rosy pink flowers. White Wood Aster is a native species that has loads of tiny white flowers with purple centers. It will tolerate light shade. The native climbing aster, Carolina Aster, is hardy only to Zone 7. It has light-pink flowers with a light, pleasant scent. Other asters include Lady in Black, which has deep-purple foliage and hundreds of tiny white daisies with pink centers; October Skies, a bright-blue-flowered plant only 18 inches high and excellent as a groundcover, and Alert, a dwarf aster with red flowers. Silky Aster is a native that has silvery-gray leaves and rose-violet flowers. Wonder of Staffa has lavender flowers that begin in late June and keep blooming until frost. Pink Star is a two-foot mound smothered with small, soft-pink flowers. Nanus is a tiny plant, 12 inches, with shiny green leaves and sky-blue flowers.

Using asters
Asters are excellent for fall color in borders. Native species are wonderful for naturalized gardens and attract butterflies and bees. Some aster varieties make a colorful groundcover for sunny, dry areas. Compact varieties are excellent for fall containers. Asters make good, long-lasting cut flowers and also dry well.

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