While the plant grows best in full sun, it does not do well in extreme heat. Therefore, in hot climates, or during the peak of the summer, the plants should be located in some shade, even if that curtails their bloom somewhat. If you grow diascia in containers, move the container to a protected spot.
Light
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.
Soil
Diascia prefers a slightly acidic soil pH between 6.0 and 6.5. The soil should be fertile and well-drained.
Water
Diascia needs regular water, but it doesn’t like to sit in wet soil. If growing it in a container, make sure there are adequate 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 is in the forecast, they will last even longer.
Fertilizer
A slow-release fertilizer works best. However, don’t fertilize more frequently than directed on the label, or you’ll get leggy plants.
Types of Diascia (Twinspur)
The genus Diascia comprises 70 species, both annuals and perennials. Different varieties of diascia range from about 6 to 12 inches tall and 18 inches wide. Be sure to check the specific plant description for size specs before purchasing to ensure you have enough space in your designated planting spot. Popular varieties include:
Diascia barberae ‘Blackthorn Apricot’ with soft pink flowersDiascia ‘Picadilly’, a hybrid with large white flowersDiascia ‘Flirtation Orange’ with soft orange flowersDiascia integerrima ‘Coral Canyon’ with salmon-pink flowersDiascia personata, a species with pink flowers that gets up to 4 feet tall
Pruning
Diascia does not require deadheading but if your plants start to look leggy or spent, shear them back by half and they will soon start blooming all over again.
Propagating Diascia
Diascia can be propagated from cuttings. It you live in a climate where the plant’s life cycle will naturally end with a strong fall frost, the best time to propagate it is in the spring so you take full advantage of the entire growing season:
Growing Diascia 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. Note that seed collected from any hybrid diascia won’t grow true from seed.
Potting and Repotting
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. To ensure good drainage, use containers with large drainage holes and well-draining potting mix. As diascia is mostly grown as an annual container plant, repotting won’t be necessary.
Overwintering
In USDA zones 9 through 11, the plant can survive the winter as a short-lived perennial whereas in cooler climates, it is grown as an annual and cannot be overwintered.
Common Pests & Plant Diseases
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.
How to Get Diascia to Bloom
If your diascia does not bloom, or blooms poorly, it could be lack of sunlight or lack of fertilizer. Apply a fertilizer high in phosphorus to encourage blooming.
Common Problems with Diascia
The plants are relatively care-free and do not have any particular issues.
