Ornamental · Polemoniaceae
Cup-and-saucer Vine
Cobaea scandens
Offer it full sun and a tall, sturdy support, and this easygoing fast climber will dress a wall in bell-shaped flowers by late summer.
Full sun
Every 3–7 days
75–120 days
USDA 9–11
Overview
Cup-and-saucer vine takes its sweet name straight from the flower, where a deep bell of a cup rests on a wide, leafy green saucer of a calyx. The blooms open a soft creamy green and slowly ripen to a rich violet-purple, so one plant can show you both colors at the same time. It hails from the highlands of Mexico, which is the simple reason gardeners in cooler places treat it as a tender plant rather than a year-round perennial.
The thing that will win you over is its speed. Sown from seed in late winter, it can climb 10 to 20 feet or more in one season, reaching out to grab whatever it can with the branched tendrils at the tips of its leaves. Give it a fence, an arbor, or a tall trellis and it will happily cover the whole thing by late summer.
Once it is settled and climbing, it asks very little of you, so first-timers can breathe easy. The few things it really wants are a strong support, full sun, and a light touch with feeding, because rich soil and heavy nitrogen will leave you with leaves and little else. Strike that gentle balance and it rewards you with flowers from summer until the first frost.
Care
The short version: give it full sun, a tall sturdy support, and steady, even moisture in fertile but not over-rich soil, and keep a light hand on the nitrogen so it pours its energy into flowers rather than leaves.
Light
Give this vine full sun for the most generous flowering, though a little afternoon shade won't trouble it. A spot against a warm, sunny wall suits it beautifully, since that gentle extra heat encourages both the climbing and the blooming.
Water
Keep the soil evenly moist all through the growing season and water on a regular rhythm while the vine is putting on growth. Try not to let it dry out fully in hot weather, but do make sure the ground drains freely, because it won't be happy sitting in soggy soil.
Soil
It settles in happily in loam, sand, or clay as long as the drainage is good, anywhere across a pH of 5.5 to 7.5. Reach for fertile ground rather than heavily enriched soil, since too much richness tips it toward leaves at the cost of flowers.
Temperature
The vine copes with a wide range, roughly 25°F to 90°F (-4°C to 32°C), yet it simply can't stand a hard frost. Treat it as tender and wait to move it outdoors until the cold has well and truly gone.
Humidity
Everyday outdoor humidity is plenty, so there's no number you need to chase here. What matters more is air moving through the foliage, which gently keeps in check the sap-sucking pests this vine tends to draw.
Feeding
Feed once a month through spring and summer with a balanced or lower-nitrogen liquid feed. Stay easy on the nitrogen, because too much grows a lush, leafy plant that flowers poorly, which is exactly the opposite of the show you are after.
Pruning
Grown as an annual, it hardly needs any pruning at all. Pinch the young tips to coax it into branching, and tie the stems onto their support as they rise. Where it lives on as an evergreen, cut it back in late winter to tidy its shape and clear away any diseased growth.
Repotting
Pot your seedlings up as they grow, then settle them outside once the frost has passed. For a container plant, move it to a roomier pot when the roots fill the old one or begin to creep out through the drainage holes.
Size & spacing
This is a big, generous climber that can reach 10 to 20 feet (3 to 6 m) in a single season with a spread of 3 to 6 feet (91 to 183 cm). Give it that much room and a support tall enough to carry it, and it will thank you for it.
When to plant
This is a heat-lover, and a cold snap is the only thing that ends it, so timing is on your side once you know the rhythm. Start your seed indoors in late winter, set the young plants out only after the cold has truly gone and the soil has warmed, and you will be rewarded with flowers from summer all the way to the first frost.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Start seed indoors about 8-10 weeks before last frost; sow seeds on edge and keep warm (about 68-72 degrees F), germinating in roughly 14 days.
- Plant: Transplant out after all danger of frost has passed and soil is warm.
- Harvest: Blooms summer into fall until frost; flowers open creamy-green and age to deep violet-purple, each cup sitting on a leafy green calyx saucer.
Hardiness
USDA hardiness zones: 9–11
Temperature: down to -7°C
Troubleshooting
Almost everything that goes sideways with this vine is gentle and forgiving to fix, so there is no need to fret. The common ones are a plant that pours itself into leaves instead of flowers, small sap-sucking pests on the leaf undersides, and stems left with nothing to climb. Find the picture below that matches yours and step in early.
Lots of healthy leaves but the flowers are slow to come
If your vine is green and thriving but shy on buds, take heart, because this is one of the easiest things to put right. The usual reason is too much nitrogen, which coaxes the plant into leaves instead of blooms, and a cool or shady spot can slow it further. Ease off the nitrogen, give it full sun beside a warm wall, and start your seed a little earlier next time so it has a longer, kinder season.
Fix:
- Reduce nitrogen and switch to a balanced or lower-nitrogen fertilizer
- Site in full sun against a warm wall or trellis
- Start seed earlier indoors (8-10 weeks before last frost) to lengthen the growing season
The vine sprawls or tangles instead of climbing
Don't worry if your plant is flopping over rather than reaching upward, since it simply hasn't found anything to hold. This climber grips with branched tendrils at the tips of its leaves, and without a tall, sturdy anchor those fast stems wander along the ground or lean on their neighbors. Set up a strong trellis, fence, arbor, or wall before planting, then gently guide and loosely tie the young stems until the tendrils take charge on their own.
Fix:
- Install a tall sturdy trellis, fence, arbor, or wall before or at planting
- Guide and loosely tie young stems onto the support until tendrils take hold
Curled or speckled leaves, maybe with a hint of webbing
Leaves that curl, speckle, or yellow usually mean small sap-sucking visitors have moved in, and they are easy enough to send packing. Turn a leaf over and look for soft aphids, tiny spider mites with their telltale webbing, or whiteflies that scatter into the air when you brush past. A firm spray of water knocks most of them off, and a follow-up with insecticidal soap or horticultural oil on the undersides takes care of the rest.
Fix:
- Spray off pests with a strong jet of water
- Apply insecticidal soap or horticultural oil, covering leaf undersides
- Repeat treatment and improve air circulation
Toxicity
Here is some reassuring news for homes with pets and little ones: cup-and-saucer vine is not toxic. It is absent from the ASPCA's poison lists, and no poisoning has ever turned up in animals or people, so you can let it cover a fence or arbor and rest easy. It is a plant grown for its beauty, never for the table.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
You can grow this happily around cats. A curious nibble might leave a cat with a passing tummy upset, as any strange leaf can, but nothing in this vine holds a toxin that could truly harm them.
Dogs None
Dogs are perfectly fine near this plant. A chewed stem or leaf won't put a dog in harm's way, though gulping a big mouthful of any greenery can leave the stomach a little loose for a while.
Horses Safe
Horses are safe with this vine, and there is nothing on record to suggest the foliage would trouble a grazing horse that helps itself to a taste.
Rabbits Safe
Rabbits can share a garden with this climber and come to no harm, since none of its parts carry a toxin that would bother them.
Livestock Safe
It sits easy around grazing stock, with no poisoning ever reported in cattle, goats, or sheep, so you can rest comfortably with it nearby.
Birds Safe
Birds are safe with it too, whether they are pets or visitors to the garden, because the leaves and flowers hold nothing flagged as toxic to them.
People Safe
People have nothing to fear from it, and a child who picks up a stray leaf or flower is in no danger, though this is a vine grown for its beauty rather than the dinner plate.
No special handling required; wash hands after gardening as a general practice.
Varieties
The plain species drifts from green to purple as its flowers mature, but a handful of named selections hold steady on a single color. These are the ones well worth getting to know.
'Alba'
A gentle white form whose cups hold their soft creamy-white shade instead of deepening to the usual violet-purple.
'Key Lime'
A cheerful pick whose flowers stay a fresh green to chartreuse lime rather than turning purple as they age.
'Royal Plum'
A lovely choice for anyone drawn to drama, carrying the richest, deepest purple flowers the vine has to give.
How to propagate
You can grow cup-and-saucer vine from seed when you want plenty of plants, or turn to cuttings whenever you would like to hold on to one particular color.
SeedEasy
Start indoors 8-10 weeks before last frost; transplant out after frost. · Germinates in about 14 days at 68-72 degrees F; can be slow to start, then grows rapidly.
Seed is the friendliest way to raise this vine, and most gardeners do exactly that. Sow each seed on edge in a warm tray, around 68°F to 72°F (20°C to 22°C), and begin 8 to 10 weeks before your last frost. Be patient through the roughly 14 days it takes to sprout, because once those seedlings get going they grow quickly, so wait until the frost has fully passed before settling them outdoors.
Stem cuttingsModerate
Spring or summer during active growth · Several weeks to root
If you have fallen for a particular color, taking softwood cuttings in spring or summer while the vine is growing strong is the surest way to keep it, since seed won't always carry the shade through. Give the cuttings several weeks to settle their roots, and they will be ready to plant on before you know it.
Myths
A tropical-looking vine like this is surely tricky and slow for a beginner.
Those showy bell flowers can look like a lot to take on, but you can relax, because this vine is genuinely easy and races up from seed, climbing 10 to 20 feet or more in just one season. If your winters are cold, simply treat it as a warm-season annual and enjoy starting a fresh plant each spring.