The silver-edge pincushion is a large rounded shrub or small tree with broad green leaves giving it an appearance similar to Leucospermum conocarpodendron. It has beautiful golden orb-like flower heads and is one of the few calcium-loving members of the protea family.
Large ornamental rounded shrub or small tree with a single stout main trunk covered with thick corky bark. It bears bright orange pincushion flowers, usually in clusters of three. It is tree-like in stature, up to 4 m tall and between 3 and 6 m in diameter. It is clothed with attractive, light green, broadly oblong, glabrous (hairless) leaves which are toothed at the apex. The leaves are tightly packed and overlapping, giving the plant a bulky, leafy look.
Leucospermum patersonii flowers & foliage
Leucospermum patersonii flower head
The flower heads are bright orange to crimson and very showy. They are similar to, but a bit smaller than those of Leucospermum cordifolium. The flower heads are partly enclosed by the uppermost leaves. Flowers are produced from July to December.
Leucospermum patersonii is restricted to alkaline soils on limestone outcrops between Kleinmond and Cape Agulhas. Some of its habitat has been destroyed by urban expansion, development of cut flower farms and alien invasive plants, and it is locally extinct in Hermanus. It is not currently threatened and is listed as ‘Vulnerable', but climate change predictions indicate a significant population reduction by 2025.
Distribution and habitat
Leucospermum patersonii is limited to a small distribution range along the coastal strip between Kleinmond and Agulhas ranging from 50–300 m above sea level. It is restricted to alkaline (limestone) soils where it occurs, either in dense stands or scattered populations. Its habitat is cool and wet in winter and very windy and hot and dry in summer.
Derivation of name and historical aspects
The genus Leucospermum is named from the Greek, leukos, meaning white, and sperma, seed, referring to the white or light-coloured seeds of many species. The species is named after Mr. W. H. Paterson who collected it and sent it to the National Herbarium through Dr. R. Marloth.
The genus Leucospermum is a member of the protea family. It consists of 48 species that occur in southern Africa as far north as Zimbabwe, with the majority occurring in the winter rainfall regions of Western Cape.
The brightly coloured, orange flower heads of Leucospermum patersonii are pollinated by sugarbirds and sunbirds. They perch on the flower heads or the stems and probe into the flower head in search of nectar, and in so doing, their heads and necks come into contact with the pollen presenters. The flower heads are also visited by bees and beetles, in particular the green protea beetle (Trichostetha fascicularis), but they do not assist in pollination as they don't come into contact with the pollen presenter.
Leucospermum seeds have an elaiosome, a protein-rich appendage, that attracts ants which carry the seeds to their nests underground to consume the elaiosome. This seed dispersal by ants is known as myrmecochory. After a fire, the seeds stored in the ant nests germinate after being subjected to heat. Different ant species are attracted to the fruit, but the main ant associated with this symbiotic relationship is the pugnacious ant, Anoplolepis custodiens. The ants benefit by feeding on the protein-rich elaiosomes. The plant benefits in different ways. The ants quickly gather the seeds and bury them where they are safe from birds and rodents. They also help to disperse the seeds and store them in their nutrient-rich, humus-filled nests. The seeds are carried and stored deep enough underground to protect them from fire but still within reach of the heat of fires necessary to stimulate their germination. The fruit are able to live for long periods underground and germinate after fire, when they are triggered by various cues such as changes in temperature, pH and oxygen levels in the ants' nest.
Uses and cultural aspects
Leucospermum patersonii makes an attractive garden shrub providing contrast with its light green foliage and orange flower colour from early spring until midsummer. It is a good cut flower that lasts well in a vase.
Growing Leucospermum patersonii
Leucospermum patersonii is quite easy to propagate from seed or cuttings. Sow seed in late summer to autumn (March–May). Use a well-drained medium, e.g. one of two parts coarse sand to one part leaf mould and one part loam. Cover the seeds with coarse, clean sand or milled bark and keep warm and moist. Seeds need alternating cold night and warm day temperatures to initiate germination, 4–10°C and 15–20°C, typical of autumn in the Western Cape. Germination can be induced if the seeds are soaked in a 1% solution of hydrogen peroxide for 24 hours. This oxygenates the seed and softens and loosens the seed coat, which should be rubbed off. Watering the seed tray with a fungicide will help prevent fungal disease. Germination takes 1 to 2 months and the young seedlings are ready to be potted up as soon as they have developed their first set of true leaves.
Vegetative propagation requires taking semi-hardwood tip or heel cuttings from the current season's growth from late summer to autumn (March–May). Treat with rooting hormone and place in a well-drained medium under mist with a bottom heat of about 24°C. Cuttings without bottom heat will take longer to root. Good air circulation is required to prevent fungal infection.
This species requires a sunny position with free air circulation, well-drained soil and no rich manure or strong fertilizers. Although Leucospermum patersonii is alkaline-loving it grows equally well in acidic soils. Well-rotted compost applied as mulch in autumn and in spring will supply the low levels of nutrient required. Slow-release or low doses of fertilizer can be used, but avoid fertilizers with a high phosphorus (P) content.
This species could be a wonderful specimen shrub for medium to large gardens, but although it grows vigorously it also dies easily. It is probably susceptible to root fungi such as Phytophthora and any root disturbance. It is recommended that it be planted in a spot in the garden where it can be left undisturbed.
Grafting onto a hardier rootstock is recommended to overcome its susceptibility to root disease. Leucospermum conocarpodendron is the species recommended for providing the hardy rootstock.
Grafting leucospermums: The technique is simple and the same as for Mimetes and Orothamnus. There are a number of different types of grafts, but the preferred one is called the cleft graft because it provides a strong union between the rootstock and the top part of the plant called the scion. The cleft graft involves choosing a healthy rootstock with a stem approximately 15 mm in diameter and the wood still green. A fresh young shoot is selected from the plant to be grafted. The shoot should be either the same diameter as the rootstock or may be a bit thinner.
Equipment required are sharp clean scalpels, grafting or budding tape (plastic), and a broad-spectrum fungicide and wax or tree sealer. The top of the rootstock plant is removed with one clean cut. A single sharp vertical incision, about 30 mm deep is made into the top of the cut surface of the rootstock. The cut surfaces are washed with fungicide. A fresh, sturdy shoot approximately 60–100 mm long is cut from the leucospermum plant and the basal leaves are removed. The stem is pared on either side with single clean slices producing a tapering wedge. This is inserted into the vertical cut and firmly bound in position using the tape. Tree sealer or wax is used to seal the cracks at the union to prevent water from penetrating the graft and causing disease. A clear plastic bag is placed over the graft to keep the humidity levels higher and prevent desiccation. Hoops of wire support the plastic bag. The plant is then placed in a protected position out of direct sunlight. The area should not be too warm, but the light conditions must be good.
The grafts must be closely monitored over the next few weeks. The union between the rootstock and scion will take a number of weeks, but a successful graft should be evident in three months. The plastic is slit and slowly removed to allow the graft to adapt to its surroundings.
It is important that the rootstock is chosen from a disease-resistant species and also that it assumes the same proportions as the plant to be grafted onto it. If a large protea such as Leucospermum patersonii is grafted onto a smaller species such as Leucospermum cordifolium it will outgrow the rootstock in diameter at the union, become too heavy, and the top part of the plant will fall over.
References and further reading
- Phillips, E. P. 1932. An undescribed species. Bothalia index to vol. 2. The Government Printer, Pretoria.
- Goldblatt, P. & Manning, J. 2000. Cape plants. A conspectus of the Cape flora of South Africa. Strelitzia 9. National Botanical Institute, Pretoria & Missouri Botanical Garden Press, Missouri.
- Rebelo, T. 2000. Field guide to the proteas of the Cape Peninsula. Protea Atlas Project, Cape Town.
- Smith, C.A. 1966. Common names of South African plants. Memoirs of the Botanical Survey of South Africa No. 35.
- Vogts, Marie. 1982. South Africa's Proteaceae: Know them and grow them. C. Struik, Cape Town.
- website: Plants of southern Africa: an online checklist. http://posa.sanbi.org
- website: Protea Atlas Project. http://protea.worldonline.co.za
Kirstenbosch National Botanical Garden