Cup and Saucer Vine (Cobaea scandens) is a conversation starter. The flowers have a unique shape that merits both the common names: Cup and saucer vine and Cathedral bells. The purple flowers also have an unusual color palette that is unexpectedly muted, especially when you consider the size and shape of the flowers. But this is a vigorous vine and hard to ignore in the landscape. Although Cobaea takes awhile to start blooming, the vine itself will quickly make itself at home and create a screen or cover.
- Flowers: The cup-shaped flowers are pale green as they start to open, but quickly turn purple or white, as they fill out. The opening buds have a somewhat unpleasant scent, but the fully opened flowers develop a floral-honey fragrance. The green calyx remains at the base of the flower and becomes the saucer.
- Leaves: Bright green, oblong leaves and plenty of them.
Cobaea scandens (Pronounced ko-BEE-uh SKAN-dens)
Cup and saucer vine, Cathedral bells, Monastery vine
Cobaea is only perennial in USDA Hardiness Zones 9 through 10. Cup and saucer vines are usually grown as an annual vine.
This vine needs full sun to bloom well.
Mature Plant Size
Cup and Saucer is a vigorous vine, easily growing at least 20 ft. (h) x 1 to 3 ft. (w). Once Cobaea takes off, it goes. With good growing conditions, vines can easily grow longer than 20 feet.
You'll get a lot of vine growth, early in the season. Flowers don't usually come along until mid to late summer, but they'll continue into the fall.
The sprawling vines can engulf nearby plants. Use cup and saucer vine when you want a solid cover, to screen a fence, wall, or ugly view. You can grow it in containers, but you'll need a large one, and it will need to be weighted, to hold the weight of the vine and whatever support you include for it.
If you'd like color earlier in the season, you can plant other annual flowering vines as companions.
Cup and saucer vine is not particular about soil pH. It does not need rich soil, although some organic matter will keep it growing and blooming without additional fertilizer.
You will rarely find seedlings of a cup and saucer vine. The vines grow too quickly and become very tangled. You can direct seed after all danger of frost or get a head start by starting seeds indoors, 6 to 8 weeks before your last frost.
Since the vines will get entangled, you should start them in separate pots. You will also find it helpful to insert a twiggy trellis immediately, to keep them under control.
The seeds are large, flat and tough. Soaking them in water the night before planting seems to help speed germination. Germination can be erratic, but you should see sprouts within 2 to 4 weeks.
When planting, tuck the flat seeds into the soil vertically, with the longest edge facing down, and barely cover with soil. Don't worry too much about positioning the seeds perfectly, but placing them flat and covering them with soil can cause them to rot.
They also prefer warm soil (70 to 75 degrees F.) If starting indoors, heat mats or placing the seed trays on top of the refrigerator will accomplish this.
Young cup and saucer vine plants are sensitive to the cold. Give them some protection if the temperature dips.
Start training your vines early and they'll take it from there. If you would like to control their size, you can pinch the stems when they reach the top of your support or eye level. This will encourage branching and bud set.
Keep the vines watered regularly, but don't let the soil remain wet. Go easy on the fertilizer, or you will get a lot of vine growth and few flowers. If necessary, side dress with compost in mid-summer.
There is no need to deadhead the flowers or trim the vines.
Pests and Problems
Cup and saucer vine can attract aphids, especially when the plants are young and succulent. Frequent blasts of water or a couple of treatments of insecticidal soap should control them.
Older plants can fall prey to spider mites, especially during dry weather. Again, hosing down the plants will help control the pests.