Growing Proteas and Related Genera From Seed

Tim Ingram examines this family of amazing and exciting flowers.

The distribution of plants around the world gives many clues to the geological and geographical history of the Earth. Nowhere is this more striking than in the strong affinities shown between the floras of South America, South Africa and Australasia. These three land-masses, along with Antarctica and India, are thought to have once formed a single 'super-continent' known as Gondwanaland. Many examples of links between these now widely separated continents are exhibited in their floras. The Southern Beech (Nothofagus spp.) is found in moist, temperate forests in both South America and Australasia. Other relatively familiar genera native to both of these continents include Eucryphia, Drimys and Aristotelia. These genera are found nowhere else in the world.

The floral relationship between all three continents is, however, most dramatically illustrated by the family Proteaceae. These are plants mainly of dry, even arid, regions and are particularly well represented in South Africa and Australia. Those found in South America, for example the Chilean Fire Bush (Embothrium coccineum), the Chilean Hazel (Gevuina avellana), and several species of Lomatia, are adapted to moister conditions and grow well outside in mild parts of the British Isles. Fine examples are found at Wakehurst Place in Sussex. The remainder are intolerant of excess winter moisture and frost and will only grow unprotected in exceptionally mild areas.

In Australia the Proteaceae are among the most conspicuous and distinctive members of the flora, including such genera as Banksia, Telopea, Dryandra. Grevillea and Hakea. The genus Protea itself is confined to South Africa (and here largely to the south-western Cape) and, with related genera such as Leucospermum, provides examples of some of the most spectacular flowers in the Plant Kingdom. The King Protea (P. cynaroides) for instance can have flower heads of up to 30cm (12in) across!

The individual flowers of members of the Proteaceae superficially resemble those of the. honeysuckle but are unusual in having only a single whorl of four tepals (so named because they cannot be distinguished as petals or sepals). From these emerges a very long style and stigma which is often very brightly coloured and gives the flower its distinctive appearance. In some genera the stigma doubles as a 'pollen-presenter', having received the pollen from the anthers just before the flower opens. In the Banksias and Dryabdra many hundreds of these flowers are massed together to form a composite flower-head of great intricacy and beauty. In the Protea and Telopea speciosissima these flower-heads are displayed within colourful bracts and are widely prized by flower arrangers.

Both from a botanical and a gardening viewpoint, therefore, the Proteaceae have an enduring fascination. Although few are reliably hardy in climates experiencing frequent winter frosts, they will revel in light, airy conservatories or cool greenhouses, under conditions similar to those required by many Mediterranean plants or cacti and succulents. Their very great beauty in flower commends them to the adventurous gardener willing or able to provide the specialised conditions that they require.

As seeds of the Proteaceae (and in particular of Protea and Banksia spp.) becomes more widely available, these plants are likely to regain some of the popularity they had after their initial introduction to Europe in the late eighteenth and early nineteenth century. The requirement for hot, dry summers to encourage flowering may be met by utilising the warmth absorbed and reflected by a south-facing wall or retained within a conservatory. Those who have visited the Temperate House at Kew Gardens for example will marvel at the section devoted to South African genera. My desire to experiment further with these plants has been heightened by the initiation of flowers on young plants of Banksia serratifolia and Protea nana, just two years from sowing the seed! Even in the absence of flowers the foliage of many of the Banksia in particular is striking and ornamental, and the Silver Tree (Leucadendron argenteum) is, in my eyes, amongst the most beautiful of all foliage plants.

To grow Protea and Banksia (and other Proteaceae of hot, dry climates) successfully is undoubtedly a challenge. Seed germinates fairly readily but thereafter young seedlings are particularly prone to damping off and blight fungi, which lead to their rapid death. Careful attention to compost, watering and ventilation is necessary to grow plants through to maturity. Seed is best sown in spring or early autumn in a well ventilated frame or greenhouse. Various composts have been recommended, all characterised by extreme drainage, and acidic pH, and relatively low nutrient status. A mixture of equal parts of peat, sand and fine flint grit, plus half a part of medium grade perlite, has proved successful with me; seed pots are routinely soaked after growing in a solution of fungicide (e.g. Benlate) overnight.

Germination normally occurs within four to five weeks and the young seedlings should be potted on into small 3-4in (7.5-10cm) pots before there is any risk of damage to their delicate root system. The Proteaceae characteristically form dense clusters of fine, lateral 'proteoid' roots, distributed over their normal roots and these are particularly sensitive to disturbance. Following the above procedure I have had good results with a range of Banksia, Protect and Dryandra sown this autumn (1989) in a shaded frame. An economical growing medium consists of equal parts of ericaceous compost and builders ballast. Alternatively the compost recommended by Bristol Botanic Garden (where many of these plants are grown) is: five parts of ericaceous compost, two parts sharp lime-free sand, one part lime-free grit and one part medium grade perlite.

During the summer and autumn plants are best kept outdoors in a sunny and airy position, perhaps against a south-facing house wall. Once young plants have established well they can be potted on into 7-8in (17-20cm) pots and should be relatively trouble-free, given care with watering and ventilation. Fertilisers should be used with care as in nature these are plants from dry, low nutrient soils. If used, a low phosphorus fertiliser is recommended (e.g. 18:2:4 NPK, preferably slow release) as the Proteaceae in general appear to react adversely to phosphate. Growth can be rapid in the case of more vigorous species such as Banksia serratifolia and speciosa, Protea cynaroides and Leucadendron argenteum, and plants of one to two metres in height can be expected in two years from seed. However, with limited conservatory or greenhouse space some of the smaller species of Protea, such as P. nana and P. scolymocephala, may be more suitable! Many of the Banksia form lignotubers in adaptation to bush-fires and these can be heavily pruned if growing out of bounds. Species with this habit can generally be recognised by swelling of the stem at ground level (e.g. Banksia robur, serratifolia, menziesii and spinulosa).

For those gardening in very mild localities there are several species of Protea and Banksia that may grow outside in the lee of a south-facing wall. These are plants from higher altitudes that regularly experience frost and snow during the winter. Amongst the Banksia a number are described as frost tolerant by Alex George in The Banksia Book and one, B. spinulosa, will tolerate temperatures down to at least -8C (dependant on provenance). Protea such as P. sulphurea from montane habitats should also be reasonably hardy and may need no more than overhead cover to protect them from excess winter rain. A bed of specially prepared soil in a protected spot next to a house wall could provide a quite unique and eye-catching feature in the garden. In the mild, sub-tropical gardens at Tresco on the Isles of Scilly a wide range of Protea, Banksia and related genera have been grown for many years. Even here winter temperatures can occasionally drop to as low as 25F (-4C) but will rarely linger long below freezing. In colder regions the Australian Waratahs (Telopea spp) would be worthy alternatives. These grow well in the Heath Garden at Wakehurst Place under the same conditions as Embothrium and Lomatia, viz. light woodland in a sandy, acid loam. In my experience the Telopea are particularly susceptible to fungal attack as young seedlings and are very slow to develop. However, a mature bush in full flower more than lives up to its generic epithet (which translates as 'seen from afar') and would well repay the time spent in mastering its cultivation.