Chasmanthe - Planting, Growing and Caring

Botany and description

The Chasmanthes belong to the Iridaceae family, like Irises, Gladioli, but especially Crocosmias (Montbretias), to which they are botanically quite similar. The genus Chasmanthe includes only 3 species, all native to South Africa: Chasmanthe aethiopica, Chasmanthe bicolor and Chasmanthe floribunda. The species Chasmanthe floribunda is the most commonly cultivated in our gardens. This species is nicknamed “African Flag“.

The genus name Chasmanthe comes from Greek: from “chasme” (gaping) and “anthos” (flower).

The storage organ is not a bulb, but a corm. A corm is an underground part of the stem that has swollen and serves as a nutrient storage organ. A corm looks quite like a bulb, so Chasmanthes are classified in the garden as “bulb plants”. The corm of Chasmanthes is destroyed at -5°C.

The foliage is deciduous and forms a large clump of linear, erect green leaves. The foliage dries up in late spring or early summer and disappears completely by late summer. The plant then enters its dormant phase, thus escaping the summer drought. The foliage will only re-emerge in autumn.

Flowering occurs in spring (March-April) and features tall flower spikes over a metre high. These spikes are adorned with tubular flowers arranged in two rows and zigzagging on either side of the stem. The flowers are red, orange or yellow depending on the variety (see section: our most beautiful varieties). On each flower, the very long upper petal releases long stamens with purple anthers.

In our regions, the flowers are pollinated by insects, but this is not the case in South Africa. In their natural range, the flowers are pollinated by a beautiful songbird, the Orange-breasted Sunbird (Anthobaphes violacea). This brightly coloured little bird has a very fine curved beak, which allows it to reach the nectar of the flowers and, in the process, pollinate them.

Once pollinated, the flowers give way to capsules containing seeds that can self-sow under favourable conditions. In fact, the species Chasmanthe floribunda has naturalised in southern Australia.

Chasmanthe floribunda

Our most beautiful varieties

[product sku=”15542″ blog_description=”Chasmanthe floribunda is a plant of South African origin. It forms a beautiful dense and upright clump from which sturdy flowering stems adorned with orange flowers emerge.” template=”listing1″ /]

[product sku=”15543″ blog_description=”Chasmanthe floribunda var. Duckittii is a lovely yellow-flowered form of the type species.” template=”listing1″ /]

[product sku=”15544″ blog_description=”Chasmanthe floribunda ‘Saturnus’ is an unusual South African cormous plant with autumn and winter foliage, featuring early spring flowering in fiery tones, though sensitive to frost.” template=”listing1″ /]

Planting chasmanthes

Where to plant?

Chasmanthes should only be planted in the ground in mild climates: in Mediterranean regions or along the southern part of the Atlantic coast. Elsewhere, they should only be grown in pots or in a cold greenhouse. The corms of chasmanthes are destroyed at temperatures below -5°C.

Chasmanthes prefer full sun or partial shade and a light, fresh, but well-drained soil.

When to plant?

Chasmanthes are best planted in October or April.

How to plant?

In the ground, in mild climates:

• Loosen the soil to a depth of about 10 centimetres;
• Add well-rotted compost, sand or even some gravel to lighten the soil and improve drainage;
• Plant the corms (bulbs) at a depth of 9 cm, spacing them at 5 corms per square metre;
• Cover with mulch in winter to protect the corms from severe frosts.

Note: outside Mediterranean regions, chasmanthes can also be grown like gladioli: plant them after the last frosts and lift the corms in autumn to store them in a cool, dry place. Your chasmanthes will then flower in summer.

In pots

• Choose a terracotta pot, with a drainage hole at the bottom;
• Fill it with a light substrate such as compost for Mediterranean plants;
• Plant the corms (bulbs) at a depth of 10 cm;
• Overwinter the pot in a bright, cool place, but protected from frost.

Maintenance

In the ground in mild climates (-5°C)

The plant requires little maintenance. It is drought-resistant, but the soil should remain moist during the growing season. If the soil is very dry, don’t hesitate to water for a beautiful flowering.

You can remove the faded flowers after flowering, in May.

Chasmanthe floribunda and Chasmanthe floribunda ‘Duckittii’ with yellow flowers

In the ground in other climates

You’ll need to overwinter the bulbs (as with gladioli or dahlias) in a dry, frost-free place, but not too warm.

In pots

You must bring the pot indoors in winter to a bright, frost-free location. Do not water during the dormant period. Repotting every autumn is necessary.

Diseases and Pests

Aphids may occasionally attack Chasmanthes.

→ Follow Virginie’s expert advice to prevent or control an aphid infestation.

Propagation

By sowing

If the plant is happy, you may see spontaneous seedlings appear.

Otherwise, harvest your seeds in June-July (in this case, avoid cutting the flower spikes in May, obviously). Sow them in autumn under shelter in a very well-draining substrate (half sowing compost and half river sand) at a temperature of 20°C. Keep the substrate moist until the plant germinates. In spring, when frost is no longer a concern, you can plant them out in the ground. However, you’ll need to wait 2 years for the plant to flower.

By dividing offsets

Dividing offsets can be done in March. Dig up the stump and collect the new corms around the mother plant. It’s best to leave each group of corms intact rather than separating them: the older ones can then serve as a nutrient reserve to encourage the growth of younger corms. Replant the groups of young corms elsewhere in the garden and water them.

Association

It may seem challenging to pair Chasmanthe floribunda, as these plants bring such a strong presence to the garden with the size and colour of their flowers. Nevertheless, we’ll attempt to combine them with other plants that enjoy sunshine, fresh but well-drained soil, and which flower in March-April. The ideal is to stick to warm tones with a touch of contrasting whimsy: blue!

Let’s start with a few Chasmanthe floribunda ‘Saturnus’, with their bright orange flowers. To complement this unusually coloured spring flowering, we’ll rely on reliable bulb varieties with orange flowers: Tulipa fosteriana ‘Orange Emperor’ and Crocus chrysanthus ‘Orange Monarch’.

For contrast, we’ll try a Peruvian Squill (Scilla peruviana), a tender bulbous flower native to the Mediterranean basin (despite its name), which produces a stunning flowering in the form of a broad, flattened cone, in ultramarine to vivid violet-blue.

→ Discover more ideas for pairing with chasmanthes in our advice guide!

Chasmanthe floribunda ‘Saturnus’, Tulipa fosteriana ‘Orange Emperor’, Scilla peruviana and Crocus chrysanthus ‘Orange Monarch’