Clivia robusta is probably one of the tallest members of the genus as it can grow to a height of 1.6 m in ideal conditions. It is a strong grower and thrives in swamp conditions. The flowers are pendulous and range from various shades of orange to yellow with green tips. The yellow flowering form has now been described as a new variety of C. robusta and is known as var. citrina.

Description
To the naked eye it is difficult to distinguish Clivia robusta from C. gardenii. C. robusta was described as a new species as a result of genetic analyses by Ran in New Zealand. C. robusta tends to be more robust with broader leaves than C.gardenii.

C. robusta has strap shaped, broad leaves which can reach 180mm in length. The habit is upright. Plants flower in late autumn to midwinter, producing pendulous flowers ranging from pale to dark orange with green tips. The peduncles or flower spikes are strong and hold the inflorescence above the foliage. The berries are round, green ripening to orange. Under ideal conditions, Clivia robusta is long-lived, produces buttress roots in very wet areas and can grow to a height of 1.6 m.

Conservation status
In nature this species is regarded as threatened because the natural populations are so scattered and isolated.

Distribution and habitat
Clivia robusta occurs in Pondoland, growing in marshes amongst forest species such as Syzygium cordatum, Erythrina caffra and Phoenix reclinata, in scattered isolated areas. This species is well suited to cultivation under ideal conditions. It is not frost tolerant and does best in high rainfall areas and light shade. Temperatures ranging from 5ºC to 32ºC would suit this species.

Derivation of name and historical aspects
The specific name robusta refers to the robust nature of the species. A visit a number of years ago to Kirstenbosch Botanic Garden by Dr Keith Hammett, a plant breeder from New Zealand, resulted in Graham Duncan giving him some seed of a Clivia gardenia collection which had been collected in Pondoland. This material was used to do genetic analyses which has resulted in the species C. robusta being described.

Ecology
Little is known about the pollinators of Clivia and studies are now being undertaken to discover what pollinates it. This species has adapted to growing in marshes by developing buttress roots. Seed is dispersed by birds..

Uses and cultural aspects
Traditional healers and Clivia enthusiasts remove large quantities of this species which threatens their survival in their natural habitat. Fortunately when plants are removed much of the root is left behind. These roots regenerate to form new young plants. The inhospitable marshy habitats do not prevent these collectors from removing plants. Traditional healers sell the stem of the plant for medicinal as well as magical purposes. This species is an ideal garden subject under suitable conditions

Growing Clivia robusta

Clivia robusta requires light shade, good drainage, regular feeding and watering to do well. This species is well suited to shady situations and marshy areas in the garden. Steep banks are also ideal as this helps to provide good drainage, particularly in heavy soils. The roots of the plant also help to stabilize the bank. Suitable companion plants are Scadoxus multiflorus subsp. Katharinae, Crinum moorei, Plectranthus spp, Stangeria eriopus, Asparagus densiflorus and Encephalartos villosus.

Before planting, prepare the area well by digging over and applying a generous quantity of well decomposed compost. The compost needs to be dug in. Plant the clivias half a metre apart as they are tall, strong growers. To maintain good quality plants and displays it is important to replant every five years. Thorough preparation of the site after lifting the C. robusta is essential. Dig over the area and then apply a liberal application of compost before replanting. It is also an opportunity at this time to divide the plants to increase the size of the planting if necessary.

Each year in the autumn, apply a generous layer of compost around the plants. They derive a lot of benefit from this as they are not deep rooting plants. In the summer an application of organic fertilizer can be broadcast around the root area of the plants. Alternatively, broadcast a layer of old manure around the root area.

Propagation of C. robusta is either from seed or division. As the berries start colouring, they can be harvested and all of the soft tissue should be removed. Before sowing, wash the seeds in a mild fungicide solution. The clean seeds can now be sown in a medium of milled pine bark by pressing them into the medium just below the surface. It is important to keep the bark moist at all times. This milled bark needs to be fairly fine when sowing seeds.

The seeds germinate within a month and after six months the seedlings should be transplanted into 15 cm pots, planting three to a pot to allow sufficient space for the plants to develop. Use a coarse growing medium of 12 mm bark must now be used.

Clivias are slow growers so it is important not to allow the young plants to stress as this slows down their growth. Stress is caused by lack of water, high light intensity, overheating, lack of food and poor drainage. Feed every two weeks with a general fertilizer at the recommended strength and replant the young plants at least once a year with fresh growing medium. All growing mediums deteriorate in time, become more compact, drainage becomes poor with the result that the roots start rotting because there is no longer any oxygen around the root area. So it is important to repot regularly until the plants are large enough to be planted in the garden.

Because of the environment in which clivias grow, slugs and snails are a problem particularly when the flower buds start appearing. Bait needs to be scattered around the plants to eliminate the slugs and snails. Other pests are mealybugs, amaryllis caterpillar, scale and snout beetle which all need to be eliminated by spraying with a suitable insecticide.

References and further reading

• Murray, B.G., Ran, Y., De Lange, P.J., Hammett, K.R.W., Truter, J.T. & Swanevelder, Z.H. 2004. A new species of Clivia (Amaryllidaceae) endemic to the Pondoland Centre of Endemism, South Africa. Botanical Journal of the Linnean Society 146: 369-374.
• Zwanevelder, Z.H., Forbes-Hardinge, A., Truter, J.T. & Van Wyk, A.E. 2006. A new variety of Clivia robusta (Amaryllidaceae). Bothalia 36: 66-68.
• Swanevelder, Z. H. 2003 Diversity and Population Structure of Clivia miniata Lindl (Amaryllidaceae). University of Pretoria. Pretoria.