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

Description and botany

Diascia, or diascie, is a perennial native to South Africa belonging to family Scrophulariaceae, like snapdragon. The genus comprises about 50 perennial species, most of which are tender and therefore usually grown as annuals in our climates. Among the species most commonly seen in gardens is Diascia barberae, which has given rise to many cultivars; Diascia fetcaniensis is one of the hardiest species of the genus, Diascia personata is one of the tallest and Diascia cordata is a mat-forming species.

Many hybrids have been created, such as Diascia grandiflora, and very floriferous selections such as the diascias ‘Genta’.

Habit varies according to species and cultivars; erect, more or less creeping or spreading, semi-trailing even trailing. The numerous cultivars and the regular introduction of new varieties increase the range of forms and uses.

The smallest Diascia varieties do not exceed 0.15–0.30 m in height, while the tallest form erect clumps 0.60–1 m high with up to 50 cm spreading.

Although growth is rapid, Diascia is a short-lived perennial that needs to be propagated to maintain in garden in mild climates.

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

This delicate foliage is hidden beneath a quivering cloud of small flowers. In flower from spring to first frosts, Diascia is remarkable both for its long, very generous flowering and for its wide palette of colours, constantly enriched by creation of new varieties.

The stems, erect, semi-erect or prostrate, end in spikes of light terminal clusters composed of slightly tubular flowers with five rounded fused petals, the lower petal being very broad and the two upper ones extended by two spurs characteristic of the diascia flower. They evoke snapdragon flowers and come in every shade of pink, from soft pink to salmon pink, through peach, apricot, white, fiery orange and cherry-red. Their throat is often subtly highlighted by a small halo of contrasting colour.

This tireless flowering attracts many pollinating insects until the frosts.

Diascia is a tender perennial sensitive to frost (hardy to around -8°C) and is most often grown as an annual, although the hardiest diascias can survive in the warmest regions. It is easy to cultivate in sun, in any good humus-bearing, fresh, well-drained garden soil, provided exposure is not scorching.

While annual Diascia brightens window boxes and hanging baskets and is a must for container growing, its excellent performance also allows planting in ground, in borders, along paths or in rock gardens.

Main species and varieties

Most popular

Our favourite Diascias

Diascia fetcaniensis

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

• 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 rock gardens, low borders, or casually trailing 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 in hanging baskets, planters 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 tubs, it is also splendid in rock gardens or borders, bringing 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 anywhere with its pretty pure-white flowers! In borders, hanging baskets and planters, it enhances all romantic arrangements!

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

See the product sheet

Diascia personata

A Diascia unlike any other! Probably one of the hardiest and tallest! 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, flowering abundantly all summer until the frosts. Easy to sow in hanging baskets, tubs, rock gardens and low borders.

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

See the product sheet

Planting

Where to plant Diascia?

The Diascia is a perennial from South Africa that is not very hardy! This plant, which does not tolerate severe cold and does not survive temperatures below about -8°C to -10°C for hardiest species (such as D. personata and D. fetcaniensis), is usually grown as an annual in open ground or in containers under our climates. However, it can survive mild winters in the warmest parts of the country, in perfectly drained soil and when frost periods are short.

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

Diascia needs a very sunny but not scorching position to flower profusely. In the south it will tolerate partial shade. Plant in a sheltered spot out of the wind. It prefers a fairly cool, light, rich and well-drained soil. A good humus-bearing and consistently fresh soil will make it happy! It dislikes overly dry soils and stagnant moisture.

Versatile, depending on its habit — upright, trailing or prostrate — it forms colourful clumps in naturalistic or romantic gardens, in beds, in borders, to edge a path, in hanging baskets and window boxes or as groundcover on a bank, in borders, rockeries or trailing casually over walls. It is also a good plant for a conservatory or patio.

When to plant Diascia?

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

How to plant Diascia?

In open ground

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

• Soak buckets for 1 hour before planting
• Dig a hole 2 to 3 times larger than size of 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 at centre of hole, without burying collar
• Bring soil back around roots
• Firm down
• Water

Take advantage of our tips to successfully plant annuals from plug plants

How to plant a Diascia in a pot or hanging basket

The Diascia is the perfect annual to provide long-lasting flowers in hanging baskets and window boxes! Plant into a rich, well-draining potting mix such as geranium compost, alone or mixed with other annuals. All tips for planting window boxes and hanging baskets with annual plug plants are on our blog!

• Provide a container at least 15 cm in diameter. For mixed planting, space plants 15 to 20 cm apart.
• Soak plugs well before planting
• Line bottom of container with gravel or clay pebbles
• Plant into compost, optionally add some river sand
• Fill in and firm down
• Water without waterlogging then water again whenever surface dries
• Fertilise 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 depth of 1.5 mm with compost
• Water regularly with fine spray until germination, which generally takes 14 to 21 days
• When young plants have formed 2 or 3 leaves, pot them on into buckets
• Mid-May after all risk of frost, plant out in soil, into pots or window boxes

Outdoors 

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

Follow our tips to succeed with your annual seed sowings !

Maintenance and care

Dascia is one of those very floriferous annual plants that require little care provided soil remains perfectly drained and fairly cool in summer.

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. Watering should not be excessive as plant is sensitive to excess moisture, which causes crown rot.

Mulch to retain moisture around the base with dry leaves, flax shreds to limit watering.

For specimens in pots, add liquid fertiliser for flowering plants to watering, every two weeks throughout whole growth period.

Remove dead leaves and faded flowers regularly to encourage new flowers.

In spring, pinch stems to encourage plant to ramify.

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

In cold regions from November, lift plants from open ground and store pots like conservatory plants in a cool frost-free room to bring out again the following spring.

During winter, reduce watering.

Hardly ever diseased, Diascia is unaffected by diseases; only slugs and snails threaten it as they adore its young shoots: discover our tips for controlling them!

Propagation

Diascia is a short-lived frost-tender perennial (3 years) that benefits from being made more permanent: although it survives mild winters outdoors, young plants raised from cuttings taken in summer are more vigorous. So consider taking cuttings or dividing clumps of suckering species (Diascia fetcaniensis). Sowing is also easy (follow our advice above!)

How to take cuttings of Diascia?

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

• Take 10 cm-long non-flowering stem tips
• Remove lower leaves and cut each stem just below a node
• Plant in buckets filled with potting compost and sand
• Keep substrate moist but not waterlogged until rooting
• Keep cuttings in light in a cold greenhouse over winter
• Following spring, plant out in ground or into pots in May after last frosts

Dividing clumps of Diascia

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

Associate

Flexible, spreading habit, narrow, airy silhouette, bushy or trailing, the Dascia lends itself to numerous uses and combinations. With colours that range from soft pastels to vibrant hues, it adapts to every desire, in open ground or in hanging baskets, in all natural or naturalistic gardens or romantic gardens! It is indispensable in wildflower beds, in cottage gardens and in pink-themed gardens, to which its cloud-like flowering brings lightness, charm and poetry.

An example of a border combination: Persicaria amplexicaulis (‘Fat Domino’, ‘Taurus’, ‘Blackfield’…), Salvia ‘Wendy’s Wish’, Cosmos (a mix of ‘Sonata Carmin’ and ‘Sonata Rose Clair’ will be particularly effective), Diascia (‘Breeze Blue Pastel’, for example) and, in the background, flower stems 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 as an edging, use it mixed with other low-growing plants such as Nemesia, Lithodora, silver-leaved plants and aubrietas.

Cultivars with pastel flowering will be perfect for enlivening borders alongside grey- or electric-blue-foliaged plants such as nepetas, cultivars of Helichrysum petiolare, small fescues, hostas or wormwoods.

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

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

It will enjoy the company of other annuals such as cleomes, cosmos, cornflowers and Nigellas.

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