[Ebook Việt Hoá] The Instant Guide to Healthy Houseplants: Callistephus chinensis (China aster)

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This beautiful flower can be grown either indoors as a potted plant or outdoors for long-lasting cut flowers, providing the right cultivated variety (cultivar) is selected. The dwarf ‘Pinocchio’ is best for pots, while the medium-sized ‘Milady’ is good for both pots and cuttings. Its main requirements are plenty of sunshine (though it will stand shade for part of the day), a fairly rich soil and a constant supply of moisture when flowering. Outdoors it will survive light frosts; indoors it needs a cool, airy location. It has an unfortunate susceptibility to wilt disease; but if grown in pasteurized loam or soilless media, this should not be a problem indoors. 

Light 

Needs good light at all times, with full sun for most of the day if possible. 

Temperature 

Germinate seed at 55-60°F (13-1 6°C). Once potted, plants do best at a maximum of 60°F (16°C)

Water 

Keep soil barely moist during germination and for seedlings. Young plants should be watered twice a week. Water copiously during bud stage and flowering. 

Humidity 

Cool, airy situation is best. In hot weather (over 70°F, 21°C), spray early or late in the day. 

Feeding 

Begin feeding 3 weeks after potting, using diluted liquid feed at manufacturer’s recommended strength. Feed weekly until flowering is finished . 

Soil 

Use seed potting soil (or all-purpose potting soil) for germination. Pot into loam-based or soilless potting media Always use pasteurized, not garden,soil. 

After flowering

Flowers can be cut for vases, but plants will not flower again. Discard after flowering is finished. 

Propagation 

Sow seed in early spring; cover with 1/5 inch (3 mm) of soil. Cover with plastic bag pulled taut so it does not touch soil; remove bag when first signs of growth show. Give full light after 5 days and thin out 2 inches (5 cm) apart 14 days after sowing. 

What Goes Wrong 

• Plant does not thrive: Needs feeding. Feed with di- luted liquid houseplant food weekly, as asters need rich soil. 
• Plant droops in sunshine: Too dry. Always keep soil moist, particularly when in flower, but avoid water logging. 
• Flower stems weak or do not appear: Temperatures too high or not enough light. Check conditions. Move plant to a light location with temperature about 60°F (16°C). If seedlings collapse, indicates pythium disease from unpasteurized soil or container. Destroy seedlings. 
• Tiny wingless insects on plant: Greenfly. Spray with pyrethrum-based insecticide and re-peat at weekly intervals until plants are clean. 
• Gray mold on stems and buds: Botrytis. Plant is particularly susceptible if damaged, as when flowers are cut. Spray with benomyl and keep room well ventilated. 
• Leaves curl under and become twisted:  Plum aphid. Usually affects plants grown outdoors, but can infest potted plants. Tiny in- sects can be seen on underside of leaves. Spray with insecticidal soap, malathion if outdoors. 
• Plant yellows from base; dark streaks present, leaves droopy: Aster wilt. No cure; destroy plant. Choose varieties marked WR (wilt reSistant). If leaves turn yellow with dark veining,  roots may be rotted due to  waterlogging. Maintain good drainage.
• Powdery deposit on leaves and stems, yellow foliage on established plants: Powdery mildew, which is very common. Spray with dinocap (karathane) at manufacturer’s recommended strength. 
• Leaves have dark green or yellow marks: Viral disease. No cure, but plant may flower if disease is mild. Spread by greenfly, so spray other plants as a precaution. Severely infested plants should be discarded. 
• Leaves turn pale or look faded, Undersides have brown patches: Rust disease. Spray with cop- per-based fungicide.