How to Sow
Although they can tolerate a wide range of soil conditions, most asters want full sun and rich, well-drained, evenly moist soil. Some cultivars can grow in light shade. Give aster plants plenty of room to provide good air circulation and to prevent powdery mildew. Other than needing a little pinching and staking, asters are easy to grow and require little maintenance in the garden.
How to Grow
Feed plants in the spring by topdressing with compost or well-rotted manure. You can also pinch out stem tips in the spring and again in early summer to encourage branching, more flowers, and less staking due to the shorter, sturdier growth pinched plants produce. Dont pinch after June 15 (July 1 from Zone 7 south) or you will remove the emerging flower buds. Tall asters should be staked early, in spring or very early summer. Mulch asters to keep moisture in the soil, and deadhead regularly or cut the stems back immediately after flowering to prevent cultivars from self-Sowing. Most asters will need dividing every two or three years.
Harvesting
Asters are great in perennial borders, meadows, and wild gardens designed for late-season color. They combine well with solidago, sedum, monks-hoods and ornamental grasses. For lovely cut flowers, cut aster stems when about three-quarters of the flowers have opened. Split the stems under water if they are woody to encourage water uptake.