<em>Diascia</em>: to sow, to plant, to grow

Description and botany

Diascia or Twinspur is a perennial plant native to South Africa belonging to family Scrophulariaceae, like snapdragon. Genus comprises about 50 perennial species of which most are tender and therefore usually grown as annuals in our climates. Among species most common in gardens is Diascia barberae, which has given rise to many cultivars; Diascia fetcaniensis is one of hardiest species in genus, Diascia personata one of tallest, while Diascia cordata is a spreading species.

Many hybrids have been created such as Diascia grandiflora or very floriferous selections like diascias “Genta”.

Habit varies according to species and cultivars: erect, more or less creeping or spreading, semi-trailing to trailing. Multiple cultivars and regular introduction of new varieties extend forms and uses.

Smallest Diascia varieties do not exceed 0.15 to 0.30 m in height, while tallest form erect clumps 0.6 to 1 m high with up to 50 cm spread.

Although growth is rapid, Diascia is a short-lived perennial that needs to be multiplied to persist in gardens in mild climates.

All form a small compact bush, very ramified with foliage deciduous to semi-evergreen depending on climate. Stems often very supple bear small opposite leaves, lanceolate 1–4 cm long, ovate, heart-shaped (cordate) or narrow, with margins more or less dentate, arranged at base of stems. Leaves are sometimes covered with fine velvety hairs and of medium to dark green colour.

This delicate vegetation is overtaken by a shimmering cloud of small flowers. In bloom from spring through first frosts, Diascia is remarkable for long, very floriferous display and for wide palette of colours, continually enriched by new varieties.

Stems, erect, semi-erect or prostrate, end in spikes of light terminal clusters composed of slightly tubular flowers with 5 fused rounded petals, lower petal very wide, upper two extended into two characteristic spurs of Diascia flower. They resemble snapdragon flowers and occur in all shades of pink, from pale pink to salmon-pink, including peach, apricot, white, as well as fiery orange and cherry red. Their throat is often subtly enhanced by small contrasting halo.

This tireless flowering attracts large numbers of pollinating insects until frosts.

Diascia is a tender perennial that dislikes frost (hardy to about -8°C) and is most often grown as an annual; hardiest diascias can survive in warmest areas. Easy to cultivate in non-scorching sun in any good humus-rich garden soil, fresh and well-drained.

While annual Diascia brightens window boxes and hanging baskets and is a staple of container culture, its excellent performance also allows planting in ground, in borders, along paths or in rockeries.

Main species and varieties

Most popular

Our favourite Diascias

Diascia fetcaniensis

One of the hardiest in the genus! A creeping and vigorous species prized for its abundant, long flowering. A young plant to try in not-too-cold areas in hanging baskets as well as rockeries.

• Flowering time July to December
• Height at maturity 30 cm

See the product sheet

Diascia barberae Blackthorn Apricot

A profusion of small salmon-pink flowers. Very attractive in rockeries, low borders, or trailing casually over low walls.

• Flowering time July to December
• Height at maturity 30 cm

See the product sheet

Diascia Breezee Plus Pink

A pretty annual variety, semi-trailing, flowering from June to October. Ideal for hanging baskets, window boxes or containers.

• Flowering time July to November
• Height at maturity 20 cm

See the product sheet

Diascia Breezee Plus Orange

A compact, bushy variety with large papaya-orange flowers. Unmissable in hanging baskets and planters, it is also splendid in rockeries or borders to add an exotic touch!

• Flowering time July to December
• Height at maturity 25 cm

See the product sheet

Diascia Breezee Plus White

A very floriferous variety that fits everywhere with its pretty pure-white flowering! In borders, hanging baskets and window boxes, it features in all romantic compositions!

• Flowering time June to November
• Height at maturity 25 cm

See the product sheet

Diascia personata

A diascia like no other! Probably one of the hardiest and the largest! Guaranteed impact in your perennial beds or large herbaceous borders.

• Flowering time July to December
• Height at maturity 90 cm

See the product sheet

Diascia barberae Rose Queen Seeds - Twinspur

A low-growing perennial, not very hardy, which flowers profusely all summer until the first frosts. Easy to sow in hanging baskets, planters, rockeries and low borders.

• Flowering time June to November
• Height at maturity 30 cm

See the product sheet

Planting

Where to plant Diascia?

Diascia is a South African perennial of limited hardiness! This plant, which dislikes severe cold and will not withstand temperatures below -8°C to -10°C for hardiest varieties (such as D. personata and D. fetcaniensis), is usually grown as an annual in open ground or in pots in our climate. However, it can survive mild winters in warmest areas of the country, in perfectly drained soil and where frosts are fairly short-lived.

Because of its relatively low hardiness, outside mild-climate regions it is preferable to grow it in a pot and store in an unheated room or greenhouse, protected from frost in winter, then bring out during the growing season.

Diascia needs very sunny but not scorchingly hot exposure to flower abundantly. In southern parts of the country it will tolerate partial shade. Plant in a sheltered spot, protected from wind. It prefers fairly cool, light, rich, well-drained soil. A good humus-bearing, consistently moist soil will make it very happy! It dislikes very dry soils and stagnant moisture.

Versatile, depending on habit — upright, trailing or prostrate — it forms colourful clumps in all kinds of naturalistic or romantic gardens, in beds, in borders, to edge a path, in hanging baskets and window boxes or as groundcover on a slope, in rockeries or trailing casually over low walls. Also a good conservatory or patio plant.

When to plant Diascia?

Plant our young Diascia plug plants in open ground or in pots once frosts have finished for good, in April–May depending on region. Meanwhile, you can pre-cultivate them in pots to hasten growth, in a warm bright place (conservatory, greenhouse, cold frame…) at a temperature above 14°C before placing outside.

How to plant Diascia?

In open ground

Plant about 5 to 6 plug plants of Diascia per m², alone or mixed with other species. Space plants 30 to 40 cm apart in all directions. It thrives in rich, well-drained, organic soil.

• Soak buckets for 1 hour before planting
• Dig a hole 2 to 3 times larger than plug plant rootball
• Add gravel or clay pebbles to bottom of planting hole for good drainage
• Mix excavated soil with some potting compost and coarse sand
• Place plug plant in centre of hole, without burying the collar
• Draw soil up around the roots
• Firm down
• Water

Take advantage of our advice to succeed in planting annuals from plug plants

How to plant Diascia in a pot or hanging basket

Diascia is the perfect annual to provide long-lasting colour in hanging baskets and window boxes! Plant in a rich, well-drained mixture of geranium-type potting compost, alone or mixed with other annuals. All tips for planting window boxes and hanging baskets with annuals from plug plants are on our blog!

• Choose container at least 15 cm in diameter. In mixed plantings, space plants 15 to 20 cm apart
• Soak plug plants well before planting
• Line bottom of container with gravel or clay pebbles
• Plant in potting compost, optionally add some river sand
• Fill in and firm down
• Water without waterlogging, then again as soon as surface of soil dries
• Feed regularly and place in sun

When and how to sow Diascia seeds?

Sow diascia seeds in spring in March-April under cold frame at 16°C, if outside temperatures are still below about 15°C. Choose the diascia seeds from our nursery.

In seed tray

• Sow on surface of good seed compost
• Keep warm between 18 and 20°C 
• Cover seeds lightly to 1.5 mm depth with compost
• Water regularly with fine spray; germination usually takes 14 to 21 days
• When young plants have formed 2 or 3 leaves, pot on into buckets
• In mid-May, after any risk of frost has passed, plant them out into ground, in pots or window boxes

In open ground 

• Sow diascia seeds directly, well spaced in furrows, in soil enriched with leaf mould, after last frosts, generally in May
• Cover with thin layer of substrate
• Firm down
• Water and keep soil moist until germination
• Thin to 10–15 cm

Follow our tips to succeed with sowing annual seeds!

Care and maintenance

Le Dascia fait partie de ces annuals très floriferous qui réclament peu de soins pourvu que la soil reste parfaitement drainée et assez fraîche en été.

To flower abundantly, it needs regular watering, especially during prolonged drought: water every two days but without waterlogging the soil, so that it never dries out completely. Water supplies must not be excessive because the plant is sensitive to excess moisture, which causes basal rot.

Mulch to retain moisture around the base with dry leaves, flax shavings and reduce watering.

For potted specimens, add liquid fertiliser for flowering plants to the water every 15 days throughout growth.

Regularly remove dead leaves and faded flowers to encourage new flowers.

In spring, pinch the stems to encourage the plant to branch.

In regions with mild winters, cut back clumps to ground level after flowering then spread a generous dry mulch around the base of the plant to protect it from frost.

In cold regions from November, lift plants grown in open ground and store pots as conservatory plants in a cool frost-free room to bring them out again next spring.

During winter, reduce watering.

Almost never affected by disease, Diascia is insensitive to diseases; it is only threatened by slugs and snails that love its young shoots: discover our tips to combat their attacks!

Propagation

Le Diascia is a short-lived tender perennial (3 years) that is worth preserving, because although it survives mild winters in open ground, young plants raised from cuttings taken in summer will be more vigorous. So consider taking cuttings or dividing clumps of suckering species (Diascia fetcaniensis). Sowing is also easy to do (follow our advice above!)

How to take cuttings of Diascia?

Cuttings are easy to take in spring or in June from semi-woody stems.

• Take 10 cm long stem tips without flowers
• Remove lower leaves and trim each stem back below a node
• Plant into buckets filled with potting compost and sand
• Keep moist but avoid waterlogging substrate until rooting
• Place cuttings in light in a cold greenhouse over winter
• The following spring, plant them in open ground or into pots in May after last frosts

Dividing clumps of Diascia

• In autumn or in spring, use a spade to gently separate clump divisions that include roots and a few leaves
• Replant immediately in garden or in pots
• Water to encourage root establishment

Associate

Flexible, spreading habit, narrow and airy silhouette, bushy or trailing habit of Dascia allows numerous uses and combinations. With colours alternately soft and pastel or bright and vibrant, it adapts to every desire, in open ground or in hanging baskets, in all natural or naturalistic gardens or romantic ones! Essential in wildflower beds, in cottage gardens and pink gardens, to which its cloud-like flowering adds lightness, charm and poetry.

An example of a planting combination in a bed: Persicaria amplexicaulis (‘Fat Domino’, ‘Taurus’, ‘Blackfield’…), Salvia ‘Wendy’s Wish’, Cosmos (a mix of ‘Sonata Carmin’ and ‘Sonata Rose Clair’ will be most effective), Diascia (‘Breeze Blue Pastel’ for example) and, in the background, flowering spikes of Stipa gigantea and a yellow haze of Solidago altissima

Very easy to combine, in pots mix it with other annuals such as Surfinia petunias, lobelias, morning glories and Impatiens.

At front of a bed or on an edge, use it mixed with other low-growing plants such as Nemesia, lithodora, snow-in-summer, aubrietas.

Cultivars with pastel flowering are ideal to enliven borders when planted alongside grey- or electric-blue-foliaged plants such as nepetas, cultivars of Helichrysum petiolare, small fescues, hostas or artemisias.

Within a summer bed, plant it in colourful touches among other soft-stemmed plants such as dwarf dahlias, dianthus, fuchsias or verbenas. It will make an impact in a large bed alongside summer-flowering perennials and cottage perennials such as agastaches, asters, penstemons, echinaceas, hardy geraniums or phlox, within which it will intertwine beautifully.

Another example of a combination: Diascia, Verbena rigida ‘Polaris’, Scaevola and Surfinia

It will appreciate the company of other annual flowers such as cleomes, cosmos, cornflowers and love-in-a-mist.

Paired with ivy geraniums and pelargoniums, it will hide bare base of a pink or mauve rose or of a clematis throughout the summer.