China Asters make some of the loveliest of all cut flowers. They really fill a vase, and they last for days and days. There are some tricks to growing healthy, productive plants, but great success can be had by following a couple of tried and true methods.
Season & Zone
Exposure: Full sun to light shade
Sow indoors 6-8 weeks before planting out, in peat pots or similar. Otherwise direct sow outdoors after the last frost date. Just cover the seeds. If starting indoors, provide bright light and a soil temperature of 10-15°C (65-70°F). China Aster seedlings are very susceptible to damping off, so provide good ventilation and only water from below.
Space or transplant 30-45cm (12-18″) apart. This spacing is key to success later in the season, so please follow the guidance. Do not pinch back young plants. Water regularly during dry spells. This plant is particularly sensitive to over-watering, and will not thrive if over-crowded, poorly ventilated, or situated close to a heat-reflecting surface. Mulch around the plants in summer to help keep the roots cool.
Callistephus is prone to a bacteria-like organism known as aster yellows. If yellow spots become an obvious problem, destroy any infected plant before the condition spreads to others. Practice strict garden rotation with China Asters: never plant them in the same spot year after year.