Asters range from alpine kinds forming compact, 6-in. mounds to open-branching plants 6 ft. tall. Flowers come in white or shades of blue, red, pink, lavender, or purple, mostly with yellow centers; they bloom in late summer to early fall, except as noted. Taller asters are invaluable for abundant color in large borders or among shrubs. Large sprays are effective in arrangements. Compact dwarf or cushion types make tidy edgings, mounds of color in rock gardens, good container plants. For the common annual or China aster sold at nurseries, see Callistephus chinensis. For Stokes' aster, see Stokesia laevis. Recent botanical reclassification means new names for many garden asters, as you will see below.
True asters are adapted to most soils, but growth is most luxuriant in fertile soil. Few problems except for mildew on leaves in late fall. Seldom browsed by deer. Divide in late fall or early spring. Replant vigorous young divisions from outside of clump; discard old center.
A. alpinus. ALPINE ASTER. Zones US, MS; USDA 6-7. Native to Alps, Pyrenees. Mounding plant to 1 ft. high, 112 ft. wide. Leaves 5 in. long, mostly in basal tuft. Several stems grow from the leafy clump, each with one violet-blue flower 1122 in. across. Late spring to early summer bloom. Best in cold-winter areas. White and pink forms are uncommon.
A. amellus. ITALIAN ASTER. Native to Europe, western Asia. Sturdy, hairy plant grows about 2 ft. tall, 1 12 ft. wide. Branching stems bear yellow-centered violet flowers 2 in. across.
A. cordifolius. See Symphyotrichum cordifolium
A. divaricatus. See Eurybia divaricata
A. ericoides. See Symphyotrichum ericoides
A. xfrikartii. FRIKART ASTER. One of the finest, most useful and widely adapted perennials. Hybrid between Symphyotrichum amellus and A. thomsonii, a hairy-leafed, lilac-flowered, 3-ft.-tall species native to the Himalayas. Dark green leaves; abundant clear lavender to violet-blue single flowers about 212 in. across. Open growth to 2 ft. high and wide. Blooms early summer to fallalmost all year in mild-winter areas if spent flowers are removed regularly. May be short lived. 'Wonder of Staffa' and 'Mnch' are favorites, with blossoms in lavender-blue. 'Flora's Delight', to 112 ft. high, has gray-green foliage and abundant pale lilac flowers with large yellow centers.
A. laevis. See Symphyotrichum laeve
A. lateriflorus. See Symphyotrichum lateriflorum
A. novae-angliae. See Symphyotrichum novae-angliae
A. novi-belgii. See Symphyotrichum novi-belgii
A. oblongifolium. See Symphyotrichum oblongifolium
A. patens. See Symphyotrichum patens
A. pilosus pringlei (A. pringlei). See Symphyotrichum pilosum pringlei
A. tataricus. TATARIAN ASTER. US, MS, LS, CS; USDA 6-9. Native to Siberia, China, Japan. Not for small gardens, this giant grows to 57 ft. tall and 3 ft. wide, with 2-ft.-long leaves and sheaves of inch-wide blue flowers in flat clusters in fall. Can be invasive. Takes sun or shade. 'Jindai' grows 34 ft. tall.
A. tongolensis EAST INDIES ASTER. From China, Himalayas. Dark green leaves in basal tufts; clumps grow to 112 ft. high and 1 ft. wide. Each stem bears asingle lavender-blue, orange-centered, 2-in. flower in late spring to early summer. 'Napsbury' has dark blue blooms. 'Wartburg Star' forms a dense mound and has violet-blue flowers.
A. Wood's series. 'Wood's Light Blue' is a bushy plant with dark green leaves. It grows 1112 ft. high, 1122 ft. wide, but it can be severely cut back in early summer and will still flower well at only 6 in. high, bearing an abundance of medium blue, 1-in. blossoms late in the season. 'Wood's Purple', to barely 1 ft. high and wide, has deep purple blooms.