Ornamental · Scrophulariaceae
Diascia
Diascia barberae
Loose sprays of tiny spurred blooms on a low, spreading mound.
Full sun
Every 2–4 days
USDA 8–11
8–12 in · 20–30 cm
Overview
Up close, Diascia reads as a low, spreading mat of soft foliage sprinkled with small flowers in coral, pink, rose, and orange. Each bloom is a little spurred face, and behind it sits a pair of backward-pointing spurs that gave the plant its common name, twinspur. The flowers ride on loose, airy sprays rather than tight clusters, so the whole plant has an open, drifting look.
The habit stays close to the ground and tumbles outward, which is why you see it at the front of a border, spilling over the rim of a container, or trailing from a hanging basket. It is a tender perennial grown as an annual: it lives through winter outdoors only in USDA zones 8 to 11, and in colder gardens you replant it each spring or root cuttings to keep one going.
This is a cool-season bloomer at heart. It flowers hardest in the mild stretches of spring and fall, then slows or pauses when summer turns hot, picking back up as the weather eases. It reaches 8 to 12 inches (20 to 30 cm) tall and spreads 12 to 18 inches (30 to 46 cm) wide at a moderate pace, and it is not frost-tolerant.
Care
The short version: give Diascia full sun, soil that stays evenly moist but drains well, and a monthly feeding through the growing season, and it answers with loose sprays of small spurred flowers. Keep the roots from drying out, water every 2 to 4 days and more in heat, and pinch young stems plus deadhead the spent blooms to hold a dense, flowering habit. When summer heat stalls the show, shear it back for a fresh fall flush.
Light
Give Diascia full sun for the heaviest run of small spurred flowers. It will take partial shade, and in hot-summer regions a little afternoon shade actually helps the plant hold up. Push it too far into shade, though, and the bloom thins out while the stems stretch and flop loose.
Water
Keep the soil evenly moist and never bone-dry, since dry roots shut the flowering down. Plan on water every 2 to 4 days, and more often in heat or when the plant sits in a pot or hanging basket where the soil dries fast. Containers and baskets need the closest eye, as their roots run out of moisture first.
Soil
Set Diascia in moderately fertile, organically rich ground that holds moisture yet drains freely so the roots never sit waterlogged. It is easygoing about pH, taking anything from slightly acidic to alkaline across the 6.0 to 8.0 range.
Temperature
Diascia handles a wide band, roughly 10°F to 90°F (-12°C to 32°C). It does its best flowering in the mild ends of the season and slows in real heat, and it is not frost-tolerant, so cold snaps cut it short in gardens outside its hardy zones.
Humidity
Ordinary outdoor humidity suits it, with no target level to chase. What matters more is airflow: good air circulation keeps the soft foliage dry, which in turn discourages the slugs and snails that like to chew the leaves.
Feeding
Feed monthly through the growing season with a balanced, general-purpose fertilizer made for container and bedding plants. Steady, light feeding keeps the spreading mound producing fresh sprays of bloom without pushing soft, floppy growth.
Pruning
Pinch the young stems early to force branching and a fuller, denser plant, and deadhead the faded flowers to keep new ones coming. When summer heat stalls the bloom, shear the whole plant back to spark a fresh flush of flowers as fall arrives.
Size & spacing
Expect a low mound about 8 to 12 inches (20 to 30 cm) tall that spreads 12 to 18 inches (30 to 46 cm) wide at a moderate rate. Give each plant room to fill that spread so the stems can tumble over a container edge or knit into a low ribbon at the front of a border.
When to plant
Diascia runs on the cool ends of the season, so the timing follows the frost. Start seed indoors ahead of spring, set plants out once the cold has passed, and watch the small spurred flowers open from spring, through the heat-slowed midsummer, 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
Most trouble with Diascia is cosmetic and easy to read on the plant itself: a heat-stalled flush, chewed soft leaves, or stems that have stretched thin. Each one shows in the foliage or the bloom and clears up with a simple fix.
Flower sprays thin out as the heat climbs
When midsummer turns hot, the loose sprays that once carried open coral and pink blooms go quiet, and the plant coasts on its soft, spreading foliage instead. The leaves and stems stay green and firm, so the empty look is just a heat pause, not rot or disease. Shear the spent growth back and keep the roots moist, and a fresh crop of spurred flowers 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
Torn edges and silvery streaks across the foliage
Look closely and you find the soft leaves punched with ragged holes, their margins gnawed, and the small spurred blooms nibbled at the edges. A silvery, glistening trail laced over the leaf surface gives away the culprit: snails and slugs that climb the low, spreading stems after dark or after rain. Pick them off in the evening, set traps or bait, and clear the damp debris they shelter under to keep the foliage clean.
Fix:
- Hand-pick snails and slugs in the evening
- Use traps or appropriate slug baits
Stems stretch tall and bare between leaves
Instead of a low, dense cushion, the stems run up thin and stretched, with wide bare gaps between the leaves and only scattered spurred flowers along their length. Too little pinching early on and too little sun leave the plant reaching and loose. Pinch the young growth to force side branches, deadhead the faded blooms, and shift container plants into brighter light to rebuild a tight, flower-packed habit.
Fix:
- Pinch young plants to promote branching
- Deadhead spent flowers regularly
- Move container plants to a sunnier location
Toxicity
Diascia is non-toxic across the board. It does not appear on the ASPCA toxic list, and there are no records of it poisoning cats, dogs, horses, rabbits, grazing livestock, or birds. It is not grown to be eaten, but a child who tastes a spurred flower comes to no harm.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
A cat that bites a soft leaf or a spurred bloom takes no harm from the plant itself. The worst you might see is a brief, passing bout of stomach upset from the roughage, the same mild reaction most green foliage can cause, and nothing tied to anything in Diascia.
Dogs None
A dog can nose into a basket and chew the trailing stems without danger. If a large mouthful of leaves goes down, expect at most a short, mild tummy grumble from the plant fiber, not poisoning, since there is nothing harmful in the foliage or flowers.
Horses Safe
Diascia is safe around horses. A horse that grazes the low, spreading growth meets no toxin in the leaves, stems, or coral and pink blooms.
Rabbits Safe
Rabbits can nibble the soft foliage freely. The leaves and small spurred flowers carry nothing toxic, so a curious rabbit comes to no harm.
Livestock Safe
Goats, sheep, and cattle can browse the plant without risk. None of the foliage or flowers holds anything poisonous to grazing livestock.
Birds Safe
Birds are in no danger near the loose sprays of bloom. Nothing in the leaves, stems, or spurred flowers poses a threat to them.
People Safe
Diascia is not grown to be eaten, but it is safe for people. A child who tastes a small spurred flower comes to no harm, since the plant holds no toxins.
Varieties
The named selections trade mostly on flower color and how heavily they bloom. From sheets of coral-pink to warm orange to bright rose, each one keeps the small spurred flowers and low, spreading shape while pushing one trait further.
Coral Canyon
A hardier selection that covers itself in sheets of coral-pink bloom and stands up to tougher garden conditions than most.
Flirtation Orange
A bedding and container favorite that swaps the usual pink for warm orange flowers glowing across its loose sprays.
Diamonte series
A compact, mounding group of hybrids that flower densely, packing the small spurred blooms tight in pots and hanging baskets.
Darla Rose
A vigorous grower picked for heavy flowering, throwing up bright rose-pink blooms in quantity.
How to propagate
You can build more plants two easy ways: sow seed for a fresh batch, or take soft stem cuttings to copy a hybrid exactly. Both are simple, and cuttings double as the trick for carrying a favorite color through a cold winter.
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
Seed is the simplest route. Sow it indoors 6 to 8 weeks ahead of your last frost, or scatter it outdoors a week or two before that date, and give it several weeks to sprout and settle in. Seedlings reach blooming size and open their first spurred flowers in the 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 soft, growing stem tips through spring or summer while the plant is actively pushing growth. Kept warm and moist, they strike roots in about 2 to 4 weeks. This is the surest way to carry a named hybrid through a cold winter and keep it true to its parent's flower color.
Myths
Diascia is poisonous to cats and dogs, so keep it well away from pets.
This is false. The plant does not appear on the ASPCA toxic list, no poisoning cases are on record, and you can set it among cats and dogs freely with no worry.
Diascia is a hardy perennial that overwinters in any garden, year after year.
Not so. It only lives through winter outdoors in USDA zones 8 to 11. Where it gets colder, treat it as an annual and replant each spring, or root cuttings to carry a plant over.