There is a seemingly unsolvable conundrum for the many gardeners among us who would like vertical interest and colour in summer without having to wait a year or two for shrubs or perennial climbers to develop sufficiently to flower well.
The simple answer is to sow the seed of annual climbers, which have the capacity to germinate, grow stupendously, flower generously and set seed within a few short months. They can be so imposing that they often transform the look of a garden - all for surprisingly little bother.
Annual climbers are, in fact, often perennials that are too tender to survive frost in winter; a favourite of many gardeners is the beautiful and fast-growing Cobaea scandens.
Cobaea scandens is an impressive climber and is one of the fastest-growing and most trouble-free vines you will ever grow. In its native Mexico it makes a woody, evergreen perennial. Here it grows 10ft or so over the summer and, from summer until the first frosts, produces very large and distinctive flowers that begin a greenish-white but turn to an inky purple with age.
The bell-shaped flowers are up to 5cm (2in) in diameter and have a ruff of bracts - hence its common names, cup and saucer plant or cathedral bells. The flowers are on longish stalks that hold them out in front of the leaves.
It will behave as a perennial if kept indoors in winter at about 7°C (45°F). In a very mild winter plants may survive and remain virtually evergreen,
Cobaea scandens will appeal to anyone who longs for something with panache and visual impact. It is extremely attractive when scrambling upward through trellis work, archways, over small buildings or old trees. It will also solve the problem, temporarily at least, of what to do with that bare wall and will fill the air with a very pleasant honey scent throughout the growing season.
The RHS has awarded Cobaea scandens the prestigious Award of Garden Merit (AGM).
Sowing: Sow indoors in January to March or sow in September to overwinter in a coldframe
They will flower 20 weeks from sowing and if grown in a greenhouse will flower for 8 months of the year.
Soak the seed for two hours in lukewarm water before sowing. Sow the seeds into individual small pots containing good quality seed compost. Sow 12mm (½in) deep, setting the large flat seeds on edge and sticking vertically into the soil, thinly cover with compost or perlite. Cover the pots with plastic or cling film to retain moisture and place on a windowsill or into a propagator.
The minimum temperature for germination is16°C (60°F) the ideal temperature is around 21°C (70°F). Make sure the compost is kept moist but not wet, watering from the base of the pot. Germination usually takes three weeks to four weeks.
Once germinated the seedlings should be moved to larger 12cm (5in) pots with stakes inserted so that the young stems have something around which to twine. Grow them on at a cooler temperature.
For conservatory or greenhouse plants pot on as the plants develop. For outdoor plants harden them off carefully and put the young plants out in the garden when the danger of frost is past
Grown plants against a sturdy trellis or close to a south-facing wall or fence on to which wires, netting or a frame has been attached. Plant 45cm (18in).
Cobaea does best in moist but well-drained soil, so water regularly in dry spells.
Cobaea scandens can be grown in a large pot (at least in diameter) in large cool greenhouse or conservatory, as long as suitable wires are provided for it to cling to. Any pot-grown Cobaea needs copious watering and protection against glasshouse red spider mite. They will overwinter provided that the temperature at night does not dip below 5°C.
Excellent for clambering up trellises, pagodas, walls and fences.
A native of tropical America including Mexico.
Cobaea scandens is pollinated by bats and at dusk - at about the time that bats would emerge - the flowers emit a scent that attracts them. The bats visit for nectar but as they probe the flower those protruding stamens dust their furry chests with pollen that they transport from plant to plant.
Charles Darwin was so impressed he studied Cobaea for his book The Movements and Habits of Climbing Plants (1875).
The genus Cobaea is named after Bernabé Cobo (1582-1657), a Jesuit missionary and naturalist.
Bernabé Cobo lived 61 years in Mexico and South America and much of what we know about the Inca civilization is all due to the writing of this one remarkable Spanish priest.
Arriving in Peru in 1599, he visited the former Inca capital, Cuzco, in 1609 and spent the rest of his life writing a 47 volume "History of the New World," which he completed in 1653. Cobo recorded much of the information we know about the Inca 100 years after the Spanish conquest; some of these are still in press after some four hundred or more years.
Father Cobo was beyond all doubt the ablest and most thorough student of nature and man in Spanish America during the seventeenth century. Yet, the first, and almost only, acknowledgement of his worth dates from the fourth year of the nineteenth century.
The distinguished Spanish botanist Cavanilles not only paid a handsome tribute of respect to the memory of Father Cobo in an address delivered at the Royal Botanical Gardens of Madrid, in 1804, but he gave the name of Cobæa to a genus of plants belonging to the Polemoniaceae family of Mexico, Cobæa scandens being its most striking representative.
The species name scandens simply means ‘climbing’.
The bell-shaped flowers have a ruff of bracts, hence the common names, Cup and Saucer Vine, Cathedral Bells or Monastery Bells
- Additional Information
Packet Size 20 Seeds Family Polemoniaceae Genus Cobaea Species scandens Common Name Cathedral Bells, Cup and Saucer Vine Hardiness Half Hardy Annual Flowers The flowers turn to an inky purple with age. Natural Flower Time Late summer to first frosts Height 8 to 10m (25 to 30ft) Spread 3m (9 to 10ft) Position Must have full sun Soil Well-drained/light, Chalky/alkaline Time to Sow Sow indoors in January to March or sow in September to overwinter in a coldframe Germination Usually takes three weeks to four weeks.