Proteas are famous for their beautiful, long-lasting blooms. Although indigenous to South Africa they grow well in various other parts of the world too – Australia, New Zealand, Israel, Chile, Portugal, Hawaii and small areas of southern and northern California.
Of the Proteaceae, the members of the genus Protea are best known, both here in their native South Africa and elsewhere. The first Cape plant ever to be reported was a Protea, and from the turn of the sixteenth century when those dry seed‑heads of P. neriifolia were collected, these infinitely variable plants have woven their way through the country’s history. Names like waboom (wagenboom in the original Dutch because its fine wood was used in wagon making) and suikerbossie (sugar bush) evoke strong, cultural associations, and it is fitting that the beautiful king protea, P. cynaroldes, was named South Africa’s national flower in 1976.
These are Mediterranean climate plants that grow in areas with relatively low rainfall and high summer temperatures. Because of this trait these flowers are an excellent choice in areas where water is at a premium. The flowers have a long shelf life and therefore are in high demand for floral arrangements.
Protea is also the largest and most widespread genus of the family. Beyond the borders of the Republic, 35 species occur on the African continent south of the Sahara. Of the 82 species in South Africa, 69 grow in the fynbos from Clanwilliam to Grahamstown and 13 in the summer‑rainfall region. The definitive work on the genus is Dr John Rourke’s superb, illustrated publication The Proteas of Southern Africa (1980), from which free use has been made in compiling this short account.
Proteas are readily recognized by their flower‑heads which are made up of masses of tiny florets surrounded by colourful bracts. The growth habit varies from trees up to 8m tall, to low‑growing shrubs with underground stems. Leaves, with or without leaf‑stalks, are of many different shapes, hairy or glabrous, but are always entire. In a Protea head, the spiral, nature’s favourite design, is beautifully shown. The fruit, a small dry nut, is densely covered with long straight hairs; the style persists for variable periods.
All erect Protea species with terminal heads are pollinated by birds, of which the two sugarbird species are by far the most important. The Cape sugarbird, Promerops cafer occurs from Namaqualand to King William’s Town, but from there to Limpopo Province it is replaced by Promerops gurneyi. Though these birds will feed on other flowers and insects, there is no doubt that proteas, when available, are their main diet. Their feeding habits are perfectly suited to make them excellent pollinators.
When feeding, the sugarbird perches on the inflorescence and thrusts its head and bill through the styles to reach a nectar‑filled perianth tube below. In the process, pollen is transferred to an area between the bird’s eyes. And when it alights to feed on another inflorescence, the sharp, thrusting motion of the head ensures the forcible transfer of pollen into the stigmatic groove of a presenter from which the pollen has already been cleared.
Although also attracted to Protea flowers, sunbirds feed very differently from sugarbirds. Sunbirds have shorter bills and probe through the side of deep, oblong Protea inflorescences to reach the source of nectar. Pollination is thus unlikely.
Not all proteas lend themselves to bird pollination. For example, many have hidden flower‑heads or bear heads near the ground or in an axillary position on the stems of low‑spreading shrubs. The pendulous heads of a few taller proteas are also unsuited to bird pollination. Investigations have now proved without any doubt that cryptically concealed flower‑heads are pollinated by nocturnally active rodents and it is probable that as many as 35 species are pollinated in this way.
In such proteas, the involueral bracts of their shallow, bowl‑shaped heads are fleshy and sweet, not bitter as are the bracts of other members of the genus. Also, a yeasty odour, inflexed, short, resilient styles and a copious nectar supply (which may be correlated to a time when rodent food is scarce) are features which characterise mouse‑pollinated species. Namaqua rock mice (Aethomys spp.), Verreaux (Praeomys spp.) and the Cape striped mice (Rhabdomys spp.) have all been observed with large amounts of sticky protea pollen on their snouts while foraging among the heads during the night.
In their natural habitat proteas accommodate a multitude of insects, sometimes more than 1000 per head. Some are pests, but many enjoy the nectar and pollen, or prey upon their fellow boarders without necessarily helping or harming the development of seed. Indirectly, they may also serve as an added attraction to bird pollinators.
The precise role that different insects play in the pollination of Protea flowers has yet to be satisfactorily proved. An exception, however, is the ubiquitous, green scarab beetle, Trichostetha fascicularis. This beetle, its mouth parts adapted to liquid intake, is sturdy enough to press sticky pollen firmly on to an older pollen presenter and into an open stigmatic groove.
GROWING REQUIREMENTS FOR PROTEAS
In the wild, many proteas grow in mountainous regions, on acid soils that are free-draining and low in nutrients. They experience winter rainfall, dry windy summers and periods of drought. The plants have developed a number of different adaptations to cope with these adverse conditions. Many have small leathery leaves, sometimes covered with hairs, to restrict water-loss. The dwarf species, with their stems below ground, are particularly drought resistant.
Specialised roots increase the uptake of nutrients from the infertile soils. Swellings at the base of the stems, called lignotubers, can withstand the fires that often devastate the areas where proteas grow. New shoots develop from the lignotubers and enable the plant to recolonise burnt areas.
In cultivation, the plants require acid soils (pH below 6.5) which are low in nitrates and phosphates. The soil should be a well-drained compost of low pH. A mixture of 2 parts sand to 1 part loam and 1 part leaf-mould, with the addition of a small amount of organic fertiliser, such as bonemeal, is suitable.
Good drainage is absolutely essential. Rich loams and heavy clays do not make good protea soils. If you have a heavy soil do not try to improve it by adding sand or shingle as this will often make the problem worse; the soil binds with the sand and shingle and sets like concrete. Instead add more humus. Proteas would not appreciate the rapid burst of nutrients from a rich compost so the humus used should be fairly low in nutrients. Natural leaf mould and rotted pine needles work well. To avoid these materials compacting down into a poor draining thatch, incorporate about 50% fine shingle grit by volume and combine the mix with the existing soil.
Most protea plants are sold in containers and are ready to plant right away. However, the best planting time depends on your climate. Autumn or winter is best in mild areas as this is when moisture requirements are at their lowest, while spring is the preferred time if regular frosts are expected as this allows the young plants to get well established before having to endure winter conditions.
Start by digging a hole at least twice the size of the plant’s container, this large volume of loose soil will encourage good root development.. Additional drainage material can be added to the hole if necessary, otherwise planting is just a matter of removing the plant from its container, loosening any spiralling roots before placing in the hole, then refilling the hole and firming the plant into position. Large specimens will require staking to prevent wind damage.
Some proteas can make good container plants, but you will have to be careful with your choice of potting mixes and fertilisers. Potting mixes need to be very free draining and often benefit from added coarse material such as shingle chips or pumice. Bark based mixes seem to work well but some growers feel they produce too much ethylene, which may harm the plants in the long run. Many commercial growers use soil based mixes and they generally prefer relatively poor and gritty volcanic soils.
Even plants with low nutrient demands will eventually exhaust their potting mix, so you will have to apply fertiliser occasionally. Use mild liquid fertilisers or special low-phosphate slow release pellets. Provided you are cautious the plants should respond well.
CUT FLOWER USE
Many protea plants make excellent long-lasting cut flowers. Protea flowers can all be used to make impressive large arrangements. Protea flowers dry well although they do tend to disintegrate rather suddenly after a few months.
This introduction to Proteas will be followed by a feature on propagation and cultivation, as well as a series of plant profiles featuring some of the best known Proteas. Come back soon to learn more about these remarkable, and beautiful plants.