The name of some types of aster was changed recently to symphyotrichum, but it seems likely these cottage-garden favourites will be fondly known as asters for some time to come. They give an exuberant display of colour in late summer and autumn for very little effort, and they come in so many shapes and sizes there’s a good choice for any size of garden. They’re often associated with the fungal disease powdery mildew, but the reality is that by choosing the right varieties, or by growing susceptible ones in the right conditions, the problem can largely be avoided. They are great for pollinators, too; attracting a diverse range that includes butterflies, and many different types of bee and hoverfly.
Which? Gardening magazine rated 24 commonly available varieties of perennial asters to find the best for our gardens. To discover our recommendations, subscribe online to Which? Gardening or call 029 2267 0000.
Caption: Perennial asters, such as 'Superstar', give wonderful late colour
Plant in spring in well-drained but moisture-retentive soil. Most asters do best in sun, but some will flower well in part shade, too. Water regularly until plants are well established. Mulch around the roots after planting.
Caption: Asters do best in well-drained but moisture retentive soil
CARING FOR YOUR PLANTS
Mulch in spring to retain soil moisture. Water plants as needed in the summer to stop the soil from drying out.
Divide clumps of New England and New York asters regularly to help keep them healthy. Either dig up the whole clump every two to five years, divide and replant the divisions, or dig out some of the outer shoots (with roots) of spreading varieties every year or two and replant elsewhere.
Caption: Divide asters to keep them healthy and create extra plants
Deadhead spent flowers to prevent self-seeding. When flowering finishes, stems should be cut down to ground level. Don’t compost diseased material.
Caption: Cut the plant back to ground level when flowering finishes
PESTS AND DISEASES
Powdery mildew causes a white, powdery coating on stems and leaves, and weakens plants. To help prevent it from taking hold, don’t let the soil dry out during the summer and don’t overcrowd asters with other plants. Cut out infected stems and spray susceptible varieties with a fungicide early in the season.
Verticlium wilt is a soil-borne fungus that can cause leaves to wilt and sections of the plant to die back. Unfortunately, there are no chemical controls to use against it, but plants might respond well to feeding in the following spring.