Cup and saucer vine (Cobaea scandens) is a perennial climber native to subtropic regions of Mexico. It features thin, lightweight leaves and purple flowers that resemble the shape of a cup or bell, hence the unique name. This vine is a vigorous, rapid grower that can reach up to 30 or 40 feet in its natural environment.
Start seeds indoors in the winter, then move the seedlings outdoors after the final frost in spring. Although cup and saucer vine takes awhile to start blooming, its foliage will quickly create a screen, grow over an arbor, or cover an unsightly fence.
The plant has plentiful bright green leaves that are oblong in shape. The cup-shaped flowers are pale green as they start to open, but then turn purple or white as they mature. The buds have a somewhat unpleasant scent, but once fully opened, the flowers develop a floral-honey fragrance.
|Botanical Name||Cobaea scandens|
|Common Names||Cup and saucer vine, cathedral bells|
|Plant Type||Perennial vine (typically grown as an annual)|
|Mature Size||10–20 ft. long, 3–6 ft. wide|
|Sun Exposure||Full sun|
|Soil Type||Moist but well-drained|
|Soil pH||Neutral to acidic|
|Bloom Time||Spring, summer|
|Flower Color||Green, maturing to purple|
|Hardiness Zones||9–11 (USDA)|
Cup and Saucer Vine Care
Cup and saucer vine grows so quickly that it's usually started from seed rather than from nursery plants. Direct-sow seeds in the garden in spring after all danger of frost has passed, or get a head start on your seasonal garden by starting seeds indoors six to eight weeks before your last frost in spring.
The blooms on the cup and saucer vines are primarily pollinated by bats when the plant is grown south of USDA hardiness zone 7. These flying mammals are generally harmless (and are helpful for controlling insects), but if the idea of bats flitting around your garden disturbs you, you might want to avoid this plant.
Keep in mind that this sprawling vine can easily engulf nearby plants. So, start training young and pliable vines to grow up a structure or on a trellis and they'll take it from there. To control the size of the plant, pinch off the stems when they reach the top of your support (or to your eye level)—this will encourage branching and bud set. There is no need to deadhead the flowers.
You can grow this vine in a container, but the container must be large and heavy enough to support the weight of the vine as well as any other support structure you include for it to climb on.
Cup and saucer vines need full sun to bloom well. If you live in an especially hot climate, your vines can probably tolerate a bit of afternoon shade, but you should still aim for at least six to eight hours of sunlight each day.
While your cup and saucer vine is not particular about soil pH or soil type, it does need a well-draining soil to thrive. Additionally, mixing in some organic matter into your soil will keep your plant growing strong and blooming without the addition of fertilizers.
During the plant's growing season, it will need to be watered regularly—the soil should be allowed to drain but not dry out completely in between waterings. To master this balance, test the top few inches of soil with your finger—if it's dry, it's time to water. You can dramatically decrease your watering cadence to once a month or so during the winter months.
Temperature and Humidity
As a summer annual, cup and saucer vine grows well in just about any growing zone. If grown as a perennial, it will be reliably hardy in USDA hardiness zones 10 and 11, but might die off in zone 9.
If direct-sowing seeds outdoors, be aware that young cup and saucer vine plants are sensitive to the cold, so give them some extra protection if the temperature dips below 50 degrees Fahrenheit.
Go easy on the fertilizer, or you will encourage too much vine growth and few flowers. If necessary, side-dress with compost in mid-summer for an extra boost of nutrition.
Grow Cup and Saucer Vine From Seed
Cup and saucer vine will readily self-seed, and the seedlings can be transplanted into other locations if you wish to spread your vines about. The seeds can also be collected for planting wherever you choose. They're large, flat, and tough, so soaking them in water the night before planting helps accelerate germination. Germination can be erratic, but you should see sprouts within two to four weeks. Because the vines become entangled, you should start them in separate pots filled with ordinary potting mix. You might also find it helpful to insert a trellis immediately into the pots to keep the vines under control right from the start.
Common Pests and Diseases
Cup and saucer vine can attract aphids, especially when the plants are young and succulent. Frequent blasts of water or a few treatments of insecticidal soap should control them. Older plants can also fall prey to spider mites, especially during dry weather.