Overview and Description:

Cobaea scandens is a conversation starter. The flowers have a unique shape that merits both the common names of 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 a 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 calyces remain at the base of the flower and become the saucer.
• Leaves: Bright green, oblong leaves - and plenty of them.

Botanical Name:

Cobaea scandens (Pronounced ko-BEE-uh SKAN-dens)

Common Names:

Cup and Saucer Vine, Cathedral Bells, Monastery Vine
Hardiness Zones:

USDA Hardiness Zones 9 - 10. Cobaea is usually grown as an annual vine.

Exposure

This vine really needs full sun, to bloom well.
Mature Plant Size:

20'+ (h) x 12 - 36" (w) Once Cobaea takes off, it goes. With good growing conditions, vines can easily grow longer than 20 feet.

Bloom Period

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.
Design Suggestions:

The sprawling vines can engulf nearby plants.

Use Cobaea 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 vines as companions.

Growing Tips:

Soil:Cobaea scandens is not particular about soil pH. It does not need a rich soil, although some organic matter will keep it growing and blooming without additional fertilizer.

Planting: You will rarely find seedlings of Cobaea. 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 - 8 weeks before your last frost.

Since the vines will get entangled, I recommend starting 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 -4 weeks.

When planting, tuck the 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 a warm soil (70 - 75 F.) Heat mats or placing the seed trays on top of the refrigerator will accomplish this.

Maintenance:

Young Cobaea 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 its size, you can pinch the stems when they reach the top of your support or eye level. This will encourage branching and bud setting.
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 & Problems:

Cobaea 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.