Diascia, sometimes called twinspur, is a delicate, frothy type of plant. Some varieties will spill over pots, and others tend to grow more upright. It's a relative of the snapdragon and comprises about 70 different species in South Africa, where it is a native. The varieties of diascia you see popping up at garden centers have been bred rather recently. They’re coming out with new colors and better bloomers every year.
Diascia is quickly becoming a popular plant, especially for use in containers and hanging baskets. It is reliably hardy in USDA plant hardiness zones 9 through 11. Some varieties may be hardy down to zone 7; however, Diascia generally is a short-lived, tender perennial plant that is usually grown as an annual flower.
|Plant Type||Annual flower|
|Mature Size||6 to 12 inches tall and 18 inches wide|
|Sun Exposure||Full sun to partial sun|
|Soil Type||Fertile, well-drained|
|Soil pH||6.0 to 6.5|
|Bloom Time||Spring and fall|
|Flower Color||Pink, white, coral, orange, red, plum|
|Hardiness Zones||9 to 11|
|Native Area||South Africa|
How to Grow Diascia Plants
Diascia has small, oval-shaped leaves that are dark green. Its flowers are small but profuse. Flower colors include pastels, vivid oranges and reds, and deep plums. A single long top petal makes it look like the flower is sticking out its tongue. Below this are two side petals with horn- or spur-like projections, which give diascia its common name of twinspur. Under these is one more petal that holds the sexual organs.
Diascia repeat blooms throughout the summer, although it performs best in the cool weather of spring and fall. If your plants start to look leggy or spent, shear them back by half and they will soon start blooming all over again. Different varieties of diascia range from about 6 to 12 inches tall and 18 inches wide. Be sure to check your specific plant's description for size specs before purchasing to ensure you have enough space in your designated planting spot.
You'll get the most blooms by keeping your diascia in full sun, but in really hot weather, the plant will do best when grown in partial shade, particularly afternoon shade.
Diascia prefers a slightly acidic soil pH. Something between 6.0 and 6.5 seems to be ideal. The soil should be fertile and well-drained.
Diascia needs regular water, but it doesn’t like to sit in wet soil. If growing in a container, make sure there are good drainage holes. As a general guide, water when the top 1 inch of soil or potting mix feels dry.
Temperature and Humidity
Diascia prefers cooler temperatures, and it flowers best in the spring and fall. If your plants start to fade in the heat, cut them back to a few inches and keep them watered. They will perk back up when it cools off.
Diascia is somewhat frost-tolerant and can be kept going well into the fall. If you’re willing to move your pots into the garage whenever a hard frost threatens, they will last even longer.
A time release fertilizer seems to work best. If you prefer to hand-fertilize, don’t overdo it or you’ll get leggy plants. Leggy plants can be pinched back, to keep them attractive and full.
Varieties of Diascia Plant
- Diascia barberae 'Blackthorn Apricot': Soft pink flowers; received the Royal Horticultural Society Award of Garden Merit (AGM)
- Diascia hybrid 'Dew Drops': Clear white with a yellow center, a Proven Winners plant
- Diascia hybrid ‘Flirtation Orange’: Another Proven Winners plant, with soft orange flowers
- Diascia integerrima 'Pink Adobe': A tall, soft pink diascia that is cold hardy to zone 5.
Growing Diascia in Containers
Diascia is a natural for containers. You can fill an entire container with one variety or use a single diascia as your spiller in a mixed container. Diascia also makes a lovely edging plant and will elegantly flop over sidewalks and walls or throughout rock gardens.
Growing From Seeds
It’s rare to find seed for diascia, but there are some out there. Start seeds indoors, about six to eight weeks before your last expected frost. In warm climates, diascia can also be direct seeded. The hybrid diascia won’t grow true from seed.
Diascia seed needs light to germinate, so just press the seed firmly on top of the soil; don’t cover it. It’s very important to keep the soil moist since there’s nothing insulating the seed. The seeds should germinate within two weeks.
While disease typically is not a concern for diascia, the wet environment that these plants like is also attractive to snails and slugs. You often find these slimy critters under the plant's foliage. The simplest way to mitigate the problem is to lift the plants off the ground. Otherwise, you can employ any number of standard remedies for snails and slugs to help keep them out of the area.