Aster
Deciduous Perennial

USDA Zones: 4 - 8
Light: sun - partial shade; avoid part shade in cooler regions of Zones 4 - 6 where it can promote mildew
Height:  1 to 5 feet
Width:  18 to 36 inches
Flower Colors: white plus rich shades of blue, pink, and red colors that complement autumn leaves beautifully
Bloom Time: late summer - fall
Special Features:
Attracts Butterflies
CutFlowers
Deer Resistant
Fall Color
Flowers
US Native/Wildflower
Companion Plants:
Sedum 'Autumn Joy.'

A staple of the fall garden, asters burst forth with their star-like flowers in late summer and autumn. Bloom colors include rich pinks, blues, purples, and ruby reds. They can soar to 5 feet, depending on the species, and are excellent for beds and borders as well as for cutting to bring indoors.

Several different species are available with varying hardiness, but all are grown in a similar way. Asters are highly susceptible to disfiguring powdery mildew, but with careful growing and selection of mildew-resistant varieties, this problem can be minimized.

Notable Varieties
Several types of asters are available, including the New York aster (Aster novae-angliae) and the New York aster (Aster novi-belgii). Michaelmas daisies are a cross between the two. All three types vary in height from 8 inches to 5 feet and grow well in Zones 4 to 8, doing best where it's cool and moist. The most mildew-resistant include 'Alma Potschke,' 'September Ruby,' and 'Purple Dome.'
Especially lovely and long-blooming is Frikart's aster (Aster x frikartii), which is lavender and grows to about 3 feet. It blooms from July through October and is hardy Zones 5 to 8.
Look for 'Monch' and 'Wonder of Staffa.'
Aster divaricatus is the most shade tolerant species and grows 1 to 2 feet tall.

Care
Garden soil should be moist and, ideally, rich in organic matter. When plants are a few inches tall or in late spring, cut back by half to promote better flowering and prevent flopping later on. Staking may also be needed for taller varieties. Water the soil, not the plant, to avoid mildew diseases.

Planting
Plant asters in full sun to prevent mildew, though partial afternoon shade in the South is helpful. Space plants 18 to 36 inches apart. Give plenty of room to promote good circulation and avoid mildew. Divide in spring every two years by replanting the most vigorous portions of the outside of the plant clump.

Pests and Diseases
Mildew the major problem, though rust and spittlebugs can also be a nuisance.