Description:
Perennial asters, sometimes called New England asters, have daisy-like flowers that bloom in shades of pink, rosy-lilac or deep purple. They come in a wide variety of sizes, with some less than 30 cm (1 foot) tall to others taller than 180 cm (6 feet) or more. Asters bloom in September and October and make a perfect addition to the fall garden bursting into bloom just when there seems to be a shortage of colour. Asters naturalize well and are a magnet that attracts butterflies into the garden. Good companion plants for asters are Joe-Pye weed (Eupatorium purpureum), goldenrod (Solidago), and stonecrop (Sedum). Asters also make excellent cut flowers for vases and arrangements.
How to Grow:
During the growing season asters can look a little weedy so it’s best to plant them among other perennials. In late June pinch the stems back by about half to prevent them from flopping over. This encourages a bushier plant with more blooms. You may have to stake taller varieties.
Light
Asters prefer full sun, but will tolerate light shade.
Temperature
Asters are hardy in zones 4 through 8.
Fertilizer
An all-purpose fertilizer applied once a month or a slow-release fertilizer may be used at planting time. Follow the label directions.
Watering Needs
Asters prefer moist but not wet soil. Though they will tolerate dry periods, they perform better when given water during dry periods.
Soil
Asters thrive in moist, rich soil that is well-drained.
Propagation
Asters are easily propagated by division. In fact, the plants are more robust if they are divided every two to three years. They should be divided in spring.
Asters can also be grown from seed. Sow the seed outdoors early in the season in a nursery bed and cover lightly with soil and water thoroughly. Move them to their permanent position the next season.
When to Grow
Though asters can be started from seed, purchasing transplants is the most practical method. Since most are grown and sold in pots, they can be planted any time during the season. You’ll find asters in the garden centres in both the spring and fall. However, in the spring the plants will not be in bloom. Around late summer, they begin to produce flowers and continue blooming until frost.
Tips:
Powdery mildew, a whitish growth that may appear on leaves from late June or July onwards, is the main problem with asters. Although unsightly, the disease usually does not cause lasting harm to the plants and the severity varies depending on the weather and even the cultivar. There are chemicals that can be applied to control the disease. If you opt for this route be sure to purchase the right product and follow the label directions.
Recommended Varieties:
- ‘Alma Potschke’ is an old favorite taller variety growing 1 metre or more (3 to 4 feet) tall with glowing salmon-pink blooms.
- Aster frikartii ‘Mönch’ is lavender-blue and grows 1 metre or more (3 to 4 feet) tall.
- ‘Purple Dome’ is lavender blue and grows a compact 45 cm (18 inches) tall.
- Aster laevis ‘Bluebird’ has single, violet blue flowers.
- Aster lateriflorus ‘Prince’ has unusual dusky plum-purple foliage and tiny white star-like flowers with a raspberry coloured eye.
- Aster oblongifolius ‘October Skies’ has blue flowers.