Diascia: plants, care & winter hardiness

With filigree flower tips and delicate colours, diascia transforms the garden and balcony into a blooming landscape. However, as fragile as the Diascia may seem, the spur is considered robust and quite easy to care for.

Twinspur (Diascia) brings an enchanting mood to the garden with its elegantly shaped flower. Planted in containers or hanging baskets, frost-sensitive Diascia delights as a perennial flowering patio and balcony ornamental. Everything you need to know about diascia, as well as planting, its care and winter hardiness, you will learn in this article.

Diascia: origin and characteristics

Also known as twinspur, it refers to the plant genus Diascia, which belongs to the figwort family (Scrophulariaceae). Diascia includes about 50 species native to southern Africa, where they are common in the wild. However, with the right frost protection or skilful overwintering, diascia can also be cultivated at our latitudes. In this country, Diascia hybrids are mainly used as balcony and container plants, although they can even thrive in beds in warmer climates.

Perennial herbaceous plant grows upright, creeping or overhanging in a broad, clumpy form. Here, the diascia plant can reach a height of between 15 to 50 cm. Diascia’s small, lanceolate or rounded to cordate leaves have a serrate marginal structure and are scattered on the stem. Often water beads exuded by the plant decorate its leaf surface. From the end of April until the first frosts of autumn, diascia steadily forms new, panicle-shaped, ray-shaped flowers during its blooming period. Characteristic of Diascia are its two nectar spurs. Depending on the variety and species, the flower colour varies from red or pink to orange, as well as white. Pollinated diascia flowers can subsequently develop seed pods. However, pollination is rarely successful in our country, because in its native country, diascia is pollinated by a specialised species of bees.

Diascia is often confused with Nemesia, which is also a member of the figwort family. However, since both species are non-poisonous, there is no danger in case of confusion. Similar close relatives are the snapdragon (Antirrhinum), the eyebright (Euphrasia officinalis), and the foxglove tree (Paulownia tomentosa) – once you have discovered the similarity in flowers, it is hard to miss.

Is diascia bee friendly? From the flower of diascia are two nectar spurs, which provide abundant food for specialised species of bees in southern Africa. With their elongated pairs of forelegs, these reach inside the spores. Their front legs are equipped with hairs like brushes, so they use them to collect and transfer both nectar and pollen. The nectar supply in the nectaries of the spores serves the brood of the bees as food and at the same time as building material for their nests. In Europe, this specialised bee species does not exist – our bee and butterfly species use diascia much less effectively because they lack the appropriate tools.

Species and variety diversity

There are about 50 Diascia species, all of which are known as diascia. Special varieties are also planted that have been bred from some popular Diascia species. Here we present the most beautiful diascia species and varieties:

The most popular species of diascia

• Diascia barberae: Diascia barberae grows about 15 – 25 cm high. Depending on the variety, it blooms between June and September in different colours that vary from white, salmon, pink to pinkish red. It thrives well in semi-shady to sunny locations. This species is only partly hardy and should be overwintered frost-free.

• Diascia elegans: The plant grows 20 – 30 cm high. Between June and September its pink or orange flowers bloom. It is only partly hardy and prefers sunny to full sun locations.

• Diascia personata: This very large diascia reaches a growth height of 50 – 100 cm. Its long blooming season extends from late spring into fall, when it produces pink flowers with a dark pink throat. The perennial can be planted in partial shade, sunny or full sun places. Diascia personata is well hardy.

• Diascia rigescens: Reaches a growth height of 20 – 30 cm. The species blooms pink or salmon between June and September in sunny to full sun locations. The plant is hardy only in mild conditions.

• Diascia vigilis: This species grows 20 – 30 cm high. During its short flowering period between June and August, it forms pink, orange or red flowers. It thrives especially in sunny locations. Also, this Diascia is only partly hardy and should be protected accordingly.

The most beautiful varieties

• ‘Blackthorn Apricot’: The perennial reaches a growth height of 20 – 30 cm. The flowers are salmon red in colour with a blooming period from early to late summer. It is only conditionally hardy and prefers full sun locations.
• ‘Elliots Variety’: ‘Elliots Variety’ grows 20 – 40 cm tall. It develops a light pink flower with a pink throat between early and late summer and is only winter hardy to a limited extent. Its location can be sunny to semi-shady.
• ‘Pink Queen’: This variety reaches a height of growth between 20 and 25 cm. It forms a pink flower from early to late summer and is moderately hardy. It grows well in sunny to semi-shady locations.

Planting diascia: location and method

Optimally, Diascia thrives in a full sun location, although it also grows well in partial shade. Diascia should not be exposed to extreme weather conditions such as heavy rain or wind, so it is recommended to place the plant in a sheltered place.

Diascia prefers a well water-retaining, nutrient-rich, yet well-drained substrate. Drainage is important to prevent root rot. Strongly humic loamy soils are ideally suited. The recommended soil for pot culture is a high quality potting soil such as our Plantura Organic All Purpose Compost. For the sake of the environment, this substrate is peat-free and moderately pre-fertilised according to the needs of diascia. Due to the high content of wood fibre, it has good drainage capacity. To prevent waterlogging, the bottom of the container should still be covered with a drainage layer of gravel or expanded clay.

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Diascia in a pot is ideally suited as a balcony plant. However, it can also be used as a bedding plant with its compact growth habit. However, disturbing factors such as waterlogging and high humidity are less easily controlled outdoors. Increased pathogens such as botrytris, phytium, or rhizoctonia can spread through these, leading to rot on the Diascia. Accordingly, it is recommended to cultivate diascia preferably in the tub, to better match the degree of humidity of soil and air.

In the pot, as well as in the bed, diascia is best planted in the spring, after the last frosts in May. Due to its clumpy growth habit, a planting distance of 20 to 30 cm is recommended in the open and a place at the edge of the bed. Depending on size, the pot should hold a maximum of 4 plants.

Alternatively, you can grow the seedlings yourself with purchased or your own diascia seeds:

• In February, press seeds into a pot with growing soil about 1 cm.
• Pour substrate and cover with cling film.
• Place on the windowsill at 20 °C and ventilate constantly and keep evenly moist.
• Pre-cultivate in sufficient light and not too warm for compact, beautiful young plants.
• Germination after 1 to 2 weeks.
• For the first leaf development repot young plants in a container.
• After repotting, remove several shoot tips to stimulate the formation of new side shoots and flower buds.
• Place young plants in beds or containers after the last spring frosts in May.

Tip: In areas with mild winters, seeds can be sown directly outdoors as early as late winter.

Diascia care

Diascia is quite an undemanding garden plant, so it requires little care.

Even though the perennial loves the sun, diascia should be watered regularly, even daily during intense heat. The soil must always be kept moist. Diascia tolerates only a slight drying. Water Diascia best in the morning and evening as close to the ground as possible. This is because it allows water to percolate quickly and be absorbed directly by the roots, minimising evaporation, especially on hot days.

The frugal Diascia only needs fertilising from time to time. 4 to 6 weeks after planting, you can fertilise them for the first time. If the plant was potted in our pre-fertilised Plantura Organic All Purpose Compost, it will not even be necessary to apply a fertiliser for the first time until after 2 months. From this time you may provide nutrients to the diascia every 2 weeks. A liquid fertiliser such as our Plantura Liquid Flower Food is ideal for this purpose. With its high nitrogen content, our organic fertiliser ensures healthy growth and flowering of Diascia and can be easily added to the watering water. However, for fertilising the diascia, the normal amount recommended by us should be halved.

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In order for the diascia plant to steadily produce new flowers, you can directly remove withered or dried flowers. Otherwise, Diascia puts more energy into seed formation and less into fresh flowers. Diseased plant parts should also be removed. If Diascia suddenly ceases to bloom, then it is recommended to cut back the entire twinspur plant by a third, so that it will soon unfold new flowers. Heavy pruning after the first flowering period in the fall promotes the development of new shoots.
It is also recommended to cut back the diascia plant before wintering. In this process, shoots potentially affected by pathogens are removed and further spread of the in the winter quarters or under the winter protection is contained.

Is diascia hardy?

Because Diascia is originally from warm Africa, it is not a sufficiently hardy balcony plant. Most species, including Diascia barberae, Diascia rigescens, Diascia vigilis or Diascia elegans, tolerate only low temperatures between + 1 and + 5 °C. Some species such as Diascia personata tolerate temperatures as low as – 10 °C. In our latitudes, diascia can overwinter outdoors in warm locations next to a house wall or hedge without further frost protection. The bedding and pot culture should be additionally covered with leaves or brushwood. Even before wintering perennial should be cut back to remove diseased shoots. In most locations, you should dig up diascia in the bed before winter and place it in a tub with sandy soil. The pot is then placed in a frost-free and bright place. Watering diascia in the winter should be regular, but not excessive. It is best to water the perennial as soon as the top layer of soil seems dry. Excessive humidity should be avoided at the overwintering site to prevent rot. To ensure that Diascia develops well in the new year, the plant should be cut back in the spring and repotted in new substrate.

Is Diascia poisonous?

Diascia species are not poisonous. Since there are no known incompatibilities or toxic effects, diascia can be touched by dogs, cats and humans without hesitation. However, since diascia is not a useful plant, consumption should still be avoided as a precaution.