Ornamental · Scrophulariaceae
Diascia
Diascia barberae
Cool-weather charmer that tumbles, trails, and keeps the color coming.
Full sun
Every 2–4 days
USDA 8–11
8–12 in · 20–30 cm
Overview
Diascia, better known as twinspur, hails from South Africa and grows low and spreading, making it a winner at the front of a border, tumbling over a container edge, or trailing from a hanging basket. Each small flower carries a pair of backward-pointing spurs, the quirk that earned the plant its common name, and the blooms gather in loose sprays of coral, pink, rose, and orange.
This is a cool-season bloomer that hits its stride in the mild weather of spring and fall. It flowers hardest when temperatures stay moderate and tends to slow or pause through the peak of summer heat, picking back up as things cool down. It is not frost-tolerant, so it leans on the gentler shoulders of the year.
Treat Diascia as a tender perennial grown as an annual. It only weathers winter outdoors in USDA zones 8 to 11; in colder spots, gardeners simply replant each spring or root cuttings in fall to keep a favorite going. Easygoing and quick to reward, it gives plenty of color for very little fuss.
Care
The short version: give Diascia full sun, soil that stays evenly moist but drains well, and a monthly feed through the growing season, and it will reward you with months of color. Water every 2 to 4 days so the roots never dry out, pinch and deadhead to keep it bushy and blooming, and shear it back if summer heat stalls the flowers. Grow it as an annual outside zones 8 to 11.
Light
Give Diascia full sun and it flowers its best, though it will happily take partial shade too. Where summers run hot, a little afternoon shade is a real help and keeps the plant comfortable. Skimp on light, though, and the bloom thins out while the stems stretch and flop, so aim for plenty of sun to keep growth tight and flowery.
Water
Keep the soil evenly moist and never let Diascia dry out, especially in pots and hanging baskets where roots bake faster. Plan on watering every 2 to 4 days, and step that up during hot stretches. Dry roots are the quickest way to shut down flowering, so consistent moisture is the secret to a long, steady show.
Soil
Diascia thrives in moderately fertile, organically rich soil that stays consistently moist yet drains freely. It is easygoing about pH, settling happily anywhere from 6.0 to 8.0, which spans slightly acidic to alkaline ground. Work in some organic matter and it will have everything it needs to spread and bloom.
Temperature
This is a cool-season plant at heart, comfortable across a range of 10°F to 90°F (-12°C to 32°C). It flowers most freely in the mild weather of spring and fall and slows through midsummer heat. Keep in mind it is not frost-tolerant, so protect or replace it when hard cold arrives.
Humidity
Diascia asks for nothing special on humidity and is content with ordinary outdoor air, with no target level to chase. What does pay off is good airflow around the plant: it keeps the foliage dry and makes the spot far less inviting to slugs and snails.
Feeding
Feed Diascia monthly through the growing season with a balanced, general-purpose fertilizer made for container and bedding plants. That steady, light diet fuels the constant flowering this plant is built for, so keep it on schedule and the blooms keep coming.
Pruning
A little grooming goes a long way here. Pinch young plants to push out side shoots and build a bushy shape, then deadhead spent flowers to keep new buds forming. When summer heat stalls the show, shear the whole plant back and it will reward you with a fresh flush of bloom in fall.
Size & spacing
Diascia stays low and spreading, reaching 8 to 12 inches (20 to 30 cm) tall and fanning out 12 to 18 inches (30 to 46 cm) wide at a moderate pace. That tidy, trailing habit makes it perfect for the front of a border or cascading over the edge of a container, so give each plant room to spill.
When to plant
Timing keeps Diascia on track, and it follows the rhythm of frost. Start seed indoors 6 to 8 weeks before your last spring frost, or sow outdoors a week or two before that date, then move plants out once frost danger has passed. From there it blooms from April right up to frost, carrying color across spring, summer, and into fall.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 6-8 weeks before the last spring frost; seed may also be sown outdoors 1-2 weeks before the last frost date
- Plant: After danger of frost has passed in spring
- Harvest: Spring through summer to fall (April to frost)
Hardiness
USDA hardiness zones: 8–11
Temperature: down to -12°C
Troubleshooting
Diascia is an easygoing grower, and the few hiccups it runs into are almost always cosmetic and quick to turn around. Here are the common ones and how to set them right.
Heat hits pause on the flowers
When the temperature climbs, Diascia often takes a break from blooming and the plant can look worn out. This is a seasonal pause, not a disease, and the foliage stays healthy through it. Shear the planting back and keep the roots moist, and a fresh round of flowers usually returns as the weather cools toward fall.
Fix:
- Shear the planting back to encourage a fresh flush of fall bloom
- Keep soil consistently moist during heat
Slugs and snails are grazing after dark
Tattered holes punched through the leaves and petals, trailed by a telltale silvery shine, point straight to snails and slugs. They do their feeding at night and after rain, so the damage often appears overnight. Pick them off in the evening, set out traps or baits, and clear away the damp debris where they shelter to keep the chewing in check.
Fix:
- Hand-pick snails and slugs in the evening
- Use traps or appropriate slug baits
Stretched stems are begging for sun and a pinch
Stems that shoot up tall with wide gaps between the leaves and only a scattering of flowers usually mean two things: the plant has not been pinched and it is reaching for more light. Pinch young growth to push out side branches, deadhead as you go, and shift container plants somewhere brighter. Full sun plus regular grooming turns a floppy plant into a dense, flower-packed mound.
Fix:
- Pinch young plants to promote branching
- Deadhead spent flowers regularly
- Move container plants to a sunnier location
Toxicity
Good news for animal lovers: Diascia is non-toxic across the board. It does not appear on the ASPCA toxic list, and no poisoning cases are on record, so it is safe to plant wherever pets, livestock, and people roam.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Cats can share the garden with Diascia worry-free. The plant is not on the ASPCA toxic list, and the worst a curious cat might face from a nibble is a brief, passing tummy upset from the roughage, which is true of almost any greenery.
Dogs None
Dogs are in the clear around Diascia. Nothing in the plant is toxic to them, and a stray mouthful would at most cause the mild, short-lived stomach grumble that any leafy snack can bring.
Horses Safe
Horses can graze near Diascia without trouble. It carries no known toxins for them and is safe to grow where they roam.
Rabbits Safe
Rabbits are perfectly safe around Diascia. The plant holds nothing harmful to them, so it can sit happily in a garden they visit.
Livestock Safe
Livestock such as goats, sheep, and cattle face no danger from Diascia. It is non-toxic and fine to grow where they pasture.
Birds Safe
Birds can visit Diascia freely. The plant is not toxic to them and poses no risk in spaces they share.
People Safe
People have nothing to fear from Diascia. It is not grown to be eaten, but a child who tastes a flower will come to no harm.
Varieties
Diascia comes in a fun range of named selections, each with its own twist on color, habit, or toughness. A few standouts worth seeking out:
Coral Canyon
A tougher selection that shrugs off conditions other diascias find hard, covering itself in sheets of coral-pink flowers for dependable garden performance.
Flirtation Orange
A go-to pick for beds and pots that swaps the familiar pink for warm orange blooms, bringing a brighter, sunnier glow to the planting.
Diamonte series
A compact, mounding line of hybrids bred to flower densely, making it a natural fit for containers and hanging baskets.
Darla Rose
A strong, fast grower picked for heavy flowering, loading its stems with bright rose-pink blooms all season.
How to propagate
Making more Diascia is genuinely easy, and there are two reliable routes to take. Start fresh plants from seed, or take cuttings to clone a hybrid you already love.
SeedEasy
Start indoors 6-8 weeks before the last frost, or sow outdoors 1-2 weeks before the last frost date · Several weeks to germinate and establish before blooming the same season
Growing Diascia from seed is a rewarding, beginner-friendly project. Sow indoors 6 to 8 weeks ahead of your last frost, or scatter seed in the ground a week or two before that date. Give the seedlings several weeks to sprout and settle in, and they will flower the very same season.
Stem cuttingsEasy
Take softwood cuttings during the active growing season in spring or summer · Roots in roughly 2-4 weeks under warm, moist conditions
Snip softwood cuttings while the plant is in active growth through spring or summer, and they root in about 2 to 4 weeks kept warm and moist. This is the smart move for carrying a named hybrid through a cold winter and keeping it true to type for next year.
Myths
Diascia is poisonous to cats and dogs, so keep it well away from pets.
Not so. Diascia does not appear on the ASPCA toxic list, no poisoning cases have been documented, and it is considered safe for pets. Plant it freely around the animals you love.
Diascia is a hardy perennial everywhere and will overwinter in any garden.
That holds true only in mild regions. Diascia survives winter outdoors in USDA zones 8 to 11; anywhere colder, grow it as an annual and replant each spring, or root cuttings in fall to carry a favorite over.