This dainty member of the protea family is threatened with extinction as its habitat disappears.

Mention of the name protea, conjures images of sturdy bushes with large, spectacular flower heads. Plants making up the genus Diastella are of the protea family, but far from being robust they form delicate shrublets and groundcovers with the most charming clusters of flowers.

The name 'Diastella' is derived from the Greek word diastellein, which means 'to separate'. This refers to the soft, silky flower segments that are joined at the base, but are otherwise free. The flowers are crowded into small 10-12mm diameter heads that resemble little silky-puffs. The effect is that of a single flower, but they are in fact aggregates of many flowers.

Diastella proteoides occurs on the Cape Flats from Tokai near Constantia eastwards to Eerste River and Paarl and northwards to Mamre just beyond the town of Atlantis. A quick glance at the map will reveal that most of this land has been developed for housing and farming. This plant was once abundant on the Cape Flats, but most of its southern populations have been destroyed. Small remnant populations remain near Tokai. The plant carries a status of 'vulnerable' in the Red data book and is likely to be upgraded to endangered status as land is developed north of Cape Town.

Diastella proteoides is a low growing, sprawling shrublet with long lax branches forming mats up to 3m in diameter. It has the tendency to grow up through the branches of other shrubs to a height of 0.5m, whereas normally it is lower growing. Fine linear leaves radiate from thin hairy stems that are characteristically red in colour. The small flower heads, 10mm in diameter, form at the ends of the branches. Each flower head has an attractive rosette of pointed pink star-like, hairy bracts. The little flowers aggregate in puff-like clusters from the bracts. Flowers are produced erratically throughout the year, but mainly from July to February.

This plant grows in deep, well-drained, sandy, acid soils that are poor in nutrients. It grows in full sunlight, but can be closely accompanied and partially shaded by other shrubs. The Mediterranean climate normally provides plenty of winter rain and dry summers. The habitat is also characterised by fresh to strong winds, which help to keep the foliage dry and the humidity down. This is important to know, as this plant is susceptible to the normal range of protea fungal infections that are encouraged by wet and warm conditions.

It usually produces a single small seed in each flower head, which drops to the ground when mature. These are either taken underground by ants or eaten by rodents. Seeds normally germinate in autumn after fire. Germination is much encouraged after the mature vegetation is burnt away. A burning cycle with long enough gaps to allow re-growth and adequate seed production is a necessary part of the growth cycle.

Growing Diastella proteoides

Diastella proteoides is mostly propagated from heel or tip cuttings taken in spring or autumn. The cuttings are treated with a rooting hormone used for encouraging root development of semi-hardwood cuttings. Cuttings are placed in shallow trays or preferably compartmentalised propagation trays and placed on heated benches and under mist or fog. A typical rooting medium would include equal parts milled pine bark and polystyrene pellets. Rooting is not as easy as with pincushions, but between 30 - 50% success has been achieved. Rooted cuttings are planted and grown in a sandy well-drained acid, potting medium. Regular feeding with an organic seaweed based fertiliser is recommended.

This plant has seldom been grown from seed, as it is very time consuming to collect the seed. If seed were sown it should be dusted with a fungicide to counter pre-emergence damping off and sown in late summer or autumn.

Diastella proteiodes has proved difficult to grow and sustain in a healthy condition at Kirstenbosch. This is probably because it prefers drier conditions than are the norm in the nursery or the gardens. The plant suffers from a wide range of fungal infections and therefore the cost of keeping it healthy through intervention with fungicides is prohibitive. Ex situ conservation in nurseries is therefore not a viable and sustainable option.

Conservation

In situ conservation, which is in its natural habitat, is the best option for this species. Near Cape Town, the population in the Tokai forest is very important, as it is the last viable population in the southern distribution. The heritage area at Plattekloof near Monte Vista is also important as it forms corridors of natural flora that can be preserved providing that the land is properly managed. Preservation of populations north of Cape Town has become more important with the ever-increasing pressure for land.

Ex-situ conservation in nurseries and Botanic Gardens has been mentioned as not sustainable. The only alternative is to gather a percentage of seed and put it into long storage in the Millenium Seed Bank at Wisley, which is under the jurisdiction of the Kew Botanic Garden. This will serve as an insurance against possible extinction.

References

• Adamson, R.S. & Salter, T.M. 1950. Flora of the Cape Peninsula. Juta&Co: Cape Town and Johannesburg.
• Goldblatt, P. & Manning, J. 2000. Cape Plants, A Conspectus of the Cape Flora of South Africa. Strelitzia 9. Publ. Jointly by NBI & Missouri Botanic Garden.
• Rebelo, T. 1995. SASOL Proteas, a field guide to the Proteas of Southern Africa. Fernwood Press: Cape Town.
• Vogts, M. 1982. South Africa's Proteaceae. Know them and grow them. Struik: Cape Town.

Anthony Hitchcock
Kirstenbosch National Botanical Garden
June2002