Cup and saucer vine- Cobaea scandens

Cobaea scandens

If you like interesting heirloom plants Cup and Saucer vine should be in your garden. Another common name is Cathedral Bells. This vigorous vine is native to Mexico and is grown in most of the US as an annual vine, although it is a perennial in planting zones 9 and above.  It is also grown in heated greenhouses and sunrooms as a fall and winter blooming vine often used as a screen or “curtains”.  It is perennial and evergreen inside or in planting zones 9 and higher.
If you need something covered Cup and Saucer vine may be the plant you are looking for. It’s equally good on a trellis or chain link fence and will also climb into trees and shrubs if you let it.  If you live in colder zones say zone 7 and lower you’ll probably want to start plants inside 2 months before your last spring frost to get maximum coverage before first fall frost.  But this vine grows quickly and branches out to cover a large area.  It can easily grow 10-15 feet in just the summer.  In warm areas or inside the vine can eventually cover 40-70 feet of space.
Cobaea scandens has compound leaves, consisting of 4-6 oval leaflets.  It climbs by tendrils that are often forked and have a hook at the end.  It grows upright as a seedling until it finds suitable support then will branch to cover a wider area.  Stems are a reddish purple color when young.
The flowers of Cup and Saucer vine are said to look like a teacup in a saucer but I find that quite imaginative.  The flower starts with odd looking 5 sided pale green buds which then opens and shows off the frilly inner cup like flower. The cup has a light center spot, markings along the petals pointing to the nectar in the center, darker veins and long protruding clusters of stamens. When it first opens the flower cup is pale greenish white, over a few days it darkens to pale purple and then becomes deep purple after the flower loses its pollen.  The flowers are said to have a light sweet scent, although I have never noticed it.
The color change in the flowers makes sense because in its native habitat Cobaea scandens is pollinated by bats.  White or light colors are more easily found in the dark, even by bats.  When the flower no longer needs pollination it turns dark, and hopefully the bats will leave it alone and concentrate on plants that still need pollination.
Flowers are about 2 inches wide and begin blooming in late summer.  They will continue blooming until frost outside.  People who grow the plant inside say it will continue blooming well into winter.  There is a variety of Cup and Saucer vine that stays white that is sometimes offered in catalogs but I find the color changing variety more interesting.
If flowers get pollinated a round seed capsule develops in the center of the “saucer”.  Inside are numerous flat seeds with “wings” that help distribute them.  Because seed pods sometimes form in areas outside the range of pollinating bats night flying moths or other insects may also pollinate the plant.
Growing Cup and Saucer vine
Cup and Saucer vine prefers full sun.  I have had the plants do well in light shade also.  Inside it would need the brightest conditions possible.  It’s not fussy about soil.  In areas colder than zone 9 it’s generally grown outside as an annual.  In planting zones 6 and lower you will probably want to start the seeds inside about 2 months before your last spring frost because it takes a long time to begin blooming.
Plants are seldom available so you’ll probably have to start Cup and Saucer vine from seed.  Soak the hard seeds overnight and then either plant where you want them to grow or in pots inside.  Most catalogs recommend you plant the seeds on their sides.  Germination can take 10-30 days.  Keep seedlings in a warm area with very strong light.  Transplant outside after all danger of frost has passed.  Make the plant will have something to climb on.
Outside in reasonably good soil you won’t need much fertilization.  I work in some granular slow release fertilizer at transplanting time. If you grow it inside it will need regular fertilization from late spring through its bloom period.  The plant does better if watered during dry spells, evenly moist soil produces the most growth. Disease and insect problems are rare outside. 
The toxicity of Cup and Saucer plant is a bit confusing.  It’s listed in the FDA Poison Plants data base but not on most other poisonous plants lists.  I have heard reports that chickens can eat it without problems.  There’s no edible uses listed for the plant that I can find and only one herbal use, a tea made from leaves is used as a cough remedy in its native range.  I would suggest not eating the plant.
If you like unusual heirloom flowers and enjoy vines, the Cup and Saucer vine should be in your garden next year.

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