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Genus Asters for the Garden

Aster is a large genus of herbaceous perennials and are members of the family that bear their name, Asteraceae, that also includes daisy, sunflower, and lettuce.  The genus includes weeds as well as outstanding garden plants that are valued for their summer and fall bloom.  Plants grow from creeping rhizomes and range in height from 6″ to 8′.  The leaves are alternate, undivided, and narrow.  The daisy-like flowers heads are carried singly or in cluster and consist of ray flowers surrounding a center of disc flowers that are usually yellow.  The ray flowers may be purple, lavender, pink, rose, red, or white.  The common name and genus name, Aster, comes from the Greek word aster meaning star and refers to the shape of the flower heads.

Asters thrive in enriched fertile soil on the dry side, but are susceptible to powdery mildew if too dry.  Tall and medium asters may need staking but this need can be reduced in the case of the latter by pinching one or twice in the spring.  The species can easily be propagated from seed but most of the garden asters are hybrids and must be propagated by division in early spring or fall.  Division every few years is necessary to maintain vigor with the exception of A. amellus which should be left undisturbed for 2-3 years.  Plants can also be propagated by terminal cuttings in spring or early summer.  In addition to powdery mildew, asters are susceptible to aster wilt, caused by a fungus that attacks their roots.  Asters that suffer this disease must be propagated by terminal stem cuttings.    Some asters are more susceptible to these fungi than others but applications of a fungicide starting in the beginning of July reduces the problem.  The late bloom time of asters make them especially valuable for late summer and fall when most other plants are no longer blooming or look shabby.  Low growing asters are good in rock gardens , front of a border, and containers; taller asters are suitable for the middle or back of back of the border.

 

Asters recommended for the garden:

Alpine Aster (A. alpinus) 

Low mounding plant with solitary flowers

Height: 6-23″

Leaves: 1.5-2″ long

Flowers: 2″ wide; purple with yellow center

Bloom Time: Summer

Hardiness: Zones 2-7

Outstanding Selections: 

‘Albus ‘(pure white flowers)

‘Dark Beauty’ (dark blue/purple flowers)

‘Happy End’ (rose-pink flowers)

 

Italian Aster (A. amellus)

Species rarely seen because of superiority of cultivars

Height: 2-2.5′

Leaves: Entire, sessile, hairy, 5′ long

Flowers: 2 1/2″ wide; purple rays with yellow center; single or in dense corymbs

Bloom Time:Early fall

Hardiness: Zones 5-8

Outstanding Selections:

‘Pink Zenith’ (deep pink flowers, compact plants 2′ tall)

‘Rudolph’ (violet flowers; 2-3′ tall)

‘Sonia’ (pink flowers; 1-2′ tall)

 

White Wood Aster (A. divaricatus)

Native from Maine to Georgia; cascading branches; tolerates some shade

Height: 1-2′

Leaves: 3′ long ; heart shaped

Flowers: Loose clusters of 3/4″ starry white flowers on wiry black stems

Bloom Time: Summer

Hardiness:  Zones 4-8

 

Heather Aster (A. ericoides)

Native from Maine to Minnesota south to Florida

Height: 1-3′

Leaves: Basal leaves hairy, spatulate, up to 3″ long

Flowers: 1/2″ white to blue

Bloom Time: Fall

Hardiness: Zones 3-8

Outstanding Selection: ‘Cinderella’ (white flowers with reddish centers; 2.5′ tall)

 

Frikart’s Aster (A. x frikartii)

Bushy mound of much-branched stems with loose habit; one of the best asters for the garden

Height: 2-3′

Leaves: 1-2.5″ long; fuzzy

Flowers: 2.5″ lavender-blue

Bloom Time: Mid-summer through fall

Hardiness: Zones 5-8

Outstanding Selections: 

‘Monch’ (deep blue flowers)

‘Wonder of Staffa’ (lavender-blue flowers; begins blooming earlier than ‘Monch’)

 

Smooth aster (A. laevis)

Height: 2-3.5′

Leaves: Blue-green, heart shaped basal leaves 3-5″ long

Flowers: 1″ pale lavender blue

Bloom Time: Fall

Hardiness: Zones 2-7

 

Calico Aster (A. lateriflorus)

Bushy; native to eastern and central US

Height: 2-4′

Leaves: 4-6″

Flowers: Tiny white flowers concentrated on one side of the branch

Bloom Time: Fall

Hardiness: Zones 3-8

Outstanding Selections: ‘Horizontalis’ (more compact; burgundy-red foliage; flowers with reddish discs)

 

Stiff Aster (A. liniarifolius)

Neat clumps; native to eastern and central US

Height: 1-2′

Leaves: Rough , linear, 1-1.5″ long

Flowers: Lavender pink to violet 3/4-1′ in terminal cor7mbs

Bloom Time: Late summer to early fall

Hardiness: Zones 3-8

 

Bigleaf Aster (A. macrophyllus)

Woodland aster; tolerates some shade and drought; native to northern parts of the eastern and central United States, and down the  Appalachian Mountains to Georgia

Height: 1-2.5′

Leaves: 6-8″, heart-shaped, coarsely toothed

Flowers:1′ wide white to pale-blue flowers in flat clusters

Bloom Time: Late summer through fall

Hardiness:  Zones 3-7

 

New England Aster/Michaelmas Daisy (A. novi-angliae)

Native to eastern and central US; species rarely seen because cultivars so superior

Height: 3-6′

Leaves: 3-5″

Flowers: 2″ wide purple with bright-yellow centers

Bloom Time: Late summer to fall

Hardiness: Zones 3-8

Outstanding Selections: 

‘Alma Potschke’ (deep slamon-pink flowers, dense,  3′ tall)

‘Harrington Pink’ (pale slamon-pink flowers, 3-5′ tall)

‘Hella Lacy’ (royal purple flowers; 3-4′ tall)

‘Purple Dome’ (royal purple flowers; 3′ tall)

‘September Ruby’ (ruby-red flowers, floppy, 3-5′ tall

 

New York Aster/Michaelmas Daisy (A. novi-belgii)

Native to northeastern US; species weedy but cultivars good garden plants

Height: 1-6′

Leaves: 4-7″, smooth, lanceolate

Flowers:1-1.5″ wide blue with yellow disc in densely packed clusters

Bloom Time: Late summer to fall

Hardiness: Zones 3-8

Outstanding Selections: 

‘Professor Kippenburg’ (semi double lavender blue flowers; 1′ tall)

‘Marie Ballard’ (double powder-blue flowers; 4′ tall)

‘Booningdale White’ (semidouble to double white flowers; 3.5-4′ tall)

‘Jenny’ (cerise flowers, 10-15″ tall)

 

Tartarian Aster (A. tataricus)

Tallest of off the asters and late blooming

Height: 5-8′

Leaves: 1-2′ long

Flowers: Rounded clusters of of 1.25″ pale-blue to lavender flowers

Bloom Time: Fall

Hardiness: Zones 2-8

 

Thompson’s Aster (A. thomsonii)

Bushy, long blooming plants

Height:  1-3′

Leaves: Hairy, gray-green leaves 3-4″ long

Flowers:1-2″ wide lilac-blue flowers

Bloom Time: Late summer into fall

Hardiness: Zones 5-9

Outstanding Selections: ‘Nana’ (compact dwarf less than 2′ tall)

 

East Indies Aster (A. tongolensis)

Mat forming; good for ground cover or as edger

Height:1-1.5′

Leaves: dark green, 3-4″ long

Flowers: Solitary blue to violet flowers with orange or yellow disk on leafless stems

Bloom Time: Summer

Hardiness: Zones5-8

Outstanding Selections: 

‘Berggartemn’ (2-3″ wide violet blue flowers)

‘Napsburg’ (blue flowers)