Cobaea scandens, known on its common name as Cathedral Bells or Cup and Saucer Vine is a perennial vine, often grown as annual because is too tender to survive frost in winter. It can grow up to 6 m tall and 2 m spread. In colder areas it may be grown in a large pot and kept outdoors in summer. It will behave as a perennial if you bring and keep it indoors over winter at about 7 Celsius degrees (45 F). If grown in a pot in a cool greenhouse or conservatory it needs good watering and protection against glasshouse red spider mite. In very mild winters it may survive and remain virtually evergreen, but is usually grown as an annual climber on a wall, fence or pergola. For a good development this vine will need a place in full sun and a moist but well-drained soil, with regular watering.
It is grown for its sweetly scented flowers. The cups are usually lavender, blue or white trumpets, surround by a saucer or collar of green. The flowers appear form mid summer to mid autumn. This plant has a tropical appearance because of its lush foliage and flowers with prominent stamens.
Propagate this vine by sowing seeds. Even if it will flower in the same year after sowing, it takes a while to start blooming, so it helps to start them early, in late winter or early spring. Sow seeds individually in small pots in seed compost, each seed set on its edge and thinly covered with more compost or perlite, at 18-24 Celsius degrees (65-75F). Keep soil damp but not wet, sealing in a polythene bag to retain moisture and put in a windowsill propagator. Germination takes from 21 days to a month.
When seedlings are large enough to handle they should be moved to larger pots. Give each of them a stake, so that the young stems have something around which to twine. Grow them on in cooler conditions, keeping them well watered. Harden them off for 10-15 days and plant them out in the garden when all danger of frost is past. Place them against a sturdy trellis or close to a south-facing wall or fence. For summer flowering indoors, transplant them into 20-23 cm pots, and keep the atmosphere fairly humid.
