In addition to the ones that I grow (see Asters, Part I) in my USDA zone 7 garden, there are many other aster species and cultivars that can provide color in your garden.
Actually, although I think of asters as end of the season plants, some, like Aster alpinus, flower earlier in the season.
Aster alpinus (Alpine Aster)
Flowering in late spring or early summer, this small — six to twelve inch (15 – 30cm) tall native of the mountains of Europe, Asia and the western North America is a great plant for the front of the border or the rock garden. It is rated hardy from USDA zones 4 to 9, but does best where winters are cold. They prefer well-drained, alkaline soil and need sun.
Some of the species varieties are:
dolomiticus, found on the Balkan Peninsula gets eight inches (20 cm)tall and has foliage with fine hairs held flatly against it;
polycephalus, found in Switzerland has several flower heads on each stem with the terminal heads larger than the lateral ones;
speciosus, found in Central Asia, gets up to twenty inches (50.8cm) tall and has larger flower heads than the species of a dark violet color;
Wolfii, also native to Switzerland can get to one foot (30.4cm) or more in height and has blue flowers.
There are also several cultivars, some with semi-double flowers:
‘Albus’, of course, has white flowers;
‘Coeruleus’, which has blue flowers and gets ten inches (25cm) tall;
‘Roseus’ has pale rose flowers and is six inches (15cm)tall;
‘Rubra’ has rosy-purple flowers;
‘Superbus’ has larger and more showy heads of purple flowers;
‘Dark Beauty’ gets six to twelve inches (15 – 30.4cm) tall and has deep blue flowers;
‘Goliath’ gets fifteen inches tall and has soft blue flowers;
Happy End’ gets twelve inches tall and has semidouble lavender flowers.
This is another alpine aster, native to the Cascade Mountains of Oregon and Washington. It gets seven inches (17.8cm) tall when in flower. Hortus III lists one variety, Hayenii, said to have more slender stems with leaves reaching four inches long and native to Eastern Oregon and north east Nevada to western Wyoming and Montana. I have not run across any cultivation information, but have to assume from the native locations and gravel soil in the photographs that this is a definite alpine and would require scree conditions and cold winters.
Aster amellus (Italian Aster)
Aster amellus, native to central and south eastern Europe and western Asia, has a reputation for being temperamental and a bit tricky to grow. Unlike most asters, it cannot be moved or divided in fall and may sulk for a year until it is re-established. The flowers, which bloom in mid summer, are said to be fragrant. It will get between eighteen inches and two feet (45.7 – 60.9cm) tall and form a nice, bushy clump about eighteen inches (45.7 cm) in diameter. The leaves are rough and the lowest ones can get six inches (15cm) long. It is drought resistant and long-blooming, but may be better for the experienced gardener.
The variety bessarabicus is native to Bessarabia; reaches two feet (45.7cm) tall and has dull purple flowers.
This is a popular species in Europe and a number of cultivars have been named that may be a bit difficult to find in US nurseries.
Aster divaricatus (White Wood Aster)
This rather sprawling, rhizomatous aster has woody, twiggy almost black stems. It’s found in dry woods from Main to Georgia and west to Ohio. Unlike most asters, the leaves are large (the lower ones can be seven inches (17.8 cm) long, and heart-shaped. Although not as showy as some asters, this one is particularly valuable for shady gardens because it will bloom in heavy shade and tolerates dry shade — something we have a lot of if we garden under large trees! A. divaricatus will vary between one foot and two feet (30.5 – 60.9 cm) tall and about eighteen inches in diameter. It’s best to plant them in groups and allow them to flop. They are rated hardy from USDA zones 3 to 9.
Aster dumosus (Bushy Aster)
Native from Massachusetts to Florida and Louisiana, Aster dumosus flowers prolifically in light, well drained soil and a sunny location. It will degenerate rapidly in compacted or poorly drained soil. This is one that needs division almost every year to keep blooming well. It gets about three feet (1 meter) tall and is rated hardy to USDA zones 2 and 3. Numerous cultivars, some dwarf, have been developed, among them:
‘Lady in Blue’