Proteas
The variety to be found in the continually evolving protea plant family means there's a protea to suit every garden and gardener
Ensure they thrive at your place
Most members of the family Proteaceae are now referred to simply as ‘proteas’, and this naming even has the approval of the International Protea Association. The purists, especially in South Africa, are understandably concerned at this application of the term ‘protea’ and now tend to refer to the South African protea genus collectively by its old common name, ‘sugarbush’.
Just a decade or so ago, gardeners would speak of leucadendron or leucospermum species or cultivars, but now tend to refer to them all as simply ‘proteas’. Likewise with banksia, telopea, grevillea, serruria and other genera.
It was the Swedish botanist Carl Linnaeus who in 1735 classified the proteas. Observing the variations in 24 historic engravings of what we now know as mimetes, leucadendron, leucospermum and proteas, he named them all after the legendary Greek sea god Proteus, who could change his shape at will. Linnaeus was, of course, referring to the diversity of flower and foliage depicted. In 1809 Robert Brown revised the classification of the family and described some 39 species of the actual protea genus as well as others in his paper On the Proteaceae of Jussieu.
In 1975, Johnson and Briggs in their well-known dissertation On the Proteaceae – the Evolution and Classification of a Southern Family described the Proteaceae as “the most famous of the southern angiosperm families”. That is probably a very appropriate description for this fascinating and very large plant family.
There are currently some 73 genera and more than 1500 species in the family Proteaceae, and from time to time a new species is discovered. The greatest number – some 42 genera and more than 850 species – originate from Australia, while around 14 genera and 400 species occur in Africa (330 in the south-western Cape alone). Approximately 90 species are found in Central and South America, while the rest are scattered through Madagascar, New Guinea, New Caledonia, Southeast Asia, China, southern India and New Zealand.
Adding to the intrigue of this plant family is the everincreasing number of spectacular cultivars being developed through hybridisation or simply selected from the often very variable seedlings. Manipulated hybrids often have significant advantages over the species, whether to satisfy the demanding cut-flower markets with better colours, longer stems and increased vase life, or for vigour, ease of cultivation and disease resistance.
Cultivating proteas
In their natural environment most of the better-known Proteaceae genera and species from both South Africa and Australia have adapted over a long period of time to relatively harsh environments that are often surprisingly arid and low in nutrients. In some soil types the pH may be as low as 3, extremely acid, resulting in any available nutrients being difficult to access. To cope with these difficulties the plants evolved a ‘proteoid root system’ and understanding this is the key to successful cultivation.
Proteoid rootlets are tufts of fine, waxy rootlets extending from the main roots. These are generally more prevalent during the growing periods of spring and autumn and are often close to the soil surface. These rootlets are specialised to extract nutrients from poor soils and applying fertilisers will usually affect them by either killing them off or preventing development due to excess nutrients, especially phosphorous. This may not become apparent immediately, but once the plant is stressed by dry
Adding to the intrigue of this plant family is the number of spectacular cultivars being developed through hybridisation or selected from the often variable seedlings
weather conditions or heavy flowering, the lack of proteoid rootlets means the plant cannot obtain enough water, which will inevitably result in its collapse. Similarly, excessive water can prevent aeration of the soil around the root area (the waterlogging typical of heavy, non-porous soils) and lead to rotting of the roots. However, most proteas do actually thrive on quite large amounts of water provided the soil is well drained. In fact, plentiful water is believed to help wash away the salts that can accumulate to toxic levels in drought conditions. Most knowledgeable botanists and horticulturists consider it a fallacy to call proteas ‘drought resistant’. Good drainage and ample water is essential in their successful cultivation.
Because the proteoid root system is found mainly near the surface of the soil, often amongst organic material and associated fungal hyphae, hand-hoeing or other cultivation techniques can be detrimental and should be avoided. This surface layer of organic matter appears essential to root health but can be substituted to some extent by a lawn around the plants, provided that lawn fertilisers are avoided in their proximity.
CULTIVATION REQUIREMENTS Soil types and drainage
Proteas will thrive in stony, gravelly or sandy soils as well as good silts or loam, provided it is free-draining. Even heavy river silt can grow proteas successfully if it overlies gravel to facilitate drainage. Drainage can be improved by raising planting beds. Raised planters or plots may have a layer of gravel or rubble placed on the existing soil before backfilling with soil to further aid drainage.
Some species are more tolerant of poor drainage provided the soil is not constantly wet. These include
Banksia occidentalis (red swamp banksia), Banksia robur (swamp banksia) and Banskia integrifolia (coast banksia).
pH
Most proteas prefer acid soils in the range of pH 5.5 to
pH 6.5. A few notable exceptions occur in slightly alkaline oils of around pH 7.5 – for example Protea obtusifolia and
Protea repens – but these grow equally well in mildly acid soils. Some races of the king protea, Protea cynaroides, can be found growing naturally in soils of pH 3.5, which ranks among the most acidic soils that any plant can tolerate.
Water
There is a widespread belief that because proteas tend to be dry-climate plants they don’t like water and should be kept dry. This is a certain recipe for disaster, because there is a crucial difference between ‘dry’ and ‘well-drained’. These plants do appreciate water – many commercial growers irrigate over the main growing period to promote longer flower stems. The more free-draining the soil, the more necessary it is to irrigate (heavier soils will retain moisture longer and require less water in dry periods). Young plants also will require more water in the first summer after planting to ensure successful establishment.
Some proteas, especially those that originate from relatively arid habitats, will certainly tolerate extended dry periods once they have become well established in the garden, but even these will produce larger flowers and more luxuriant growth when watered well over the main growth periods of spring and autumn.
Watering is best carried out on cooler days or during the evening when there is less evaporation.
Nutrient requirements
In their natural habitats most members of the Proteaceae grow in soils that are low in nutrients and therefore are likely to be harmed by the application of fertilisers, especially the high phosphate content of ‘general’
Serruria florida (The Blushing Bride) There is a widespread belief that because proteas tend to be dry-climate plants they don’t like water and should be kept dry. This is a certain recipe for disaster
fertilisers. Where plants are obviously struggling to grow in very poor soils or are being grown in tubs, the low-phosphate, slow-release granular fertilisers formulated for proteaceous plants can be used as per instructions. They should be applied during the weeks leading up to the main growth periods of spring and autumn.
In some cases, particularly with commercial flower growing, the application of nitrogen in the form of ammonium sulphate or urea can be beneficial. This is applied sparingly three times a year from early spring at two-month intervals. In normal, home-garden situations, however, this is not usually necessary.
SITE PREPARATION The elimination of competition
in the form of persistent weeds is an essential part of site preparation for any type of planting.
While planting can be carried out at any time of year, newly planted proteas will require extra watering to ensure survival. However, there are two preferable times for planting that are dictated largely by climate.
In cooler regions it is better to plant in spring when the heaviest frosts are over. This enables plants to become established and acclimatised without setback and achieve some size before the onset of winter. Autumn growth will also have a chance to become hardened before frost occurs. Spring planting will also have the obvious downside of summer watering becoming more important to the survival of young plants.
In milder regions with minimal or no frosts, the optimal time is autumn and winter. Planting in these seasons enables the plants to get their roots settled and spreading into the surrounding soil before the dryness and heat of summer arrives (this general statement obviously is intended to apply to regions of mainly winter rainfall). Most growers find that less losses occur when they are able to plant over winter.
When planting young protea plants, basic common sense procedures that apply to most plants should be followed. Don’t be tempted to use a post-hole borer as this can glaze the sides of the hole in heavier soil types and thus prevent root penetration. Dig a planting hole approximately twice the size of the bag or pot and then partially backfill with the loosened soil. This enables the roots to spread easily into the surrounding soil thus ensuring firm anchorage and quick access to moisture and nutrients.
Unless soil is already moist, water the plant in well at planting and at least weekly after that, particularly in dry weather conditions.
Newly planted large specimens will require staking to eliminate rocking in high winds. Drive the stake in at an angle away from the trunk to avoid root damage. To secure the plant, select materials that ‘breathe’, such as old stockings or foamcovered ties. When plants are established and fully stabilised and rooted into the soil, stakes should be removed to enable the plant to naturally develop its own support.
The ideal is to plant smaller-grade shrubs that establish themselves and bush up quickly so that minimal, if any, staking is required. Large, smooth rocks can be placed around the trunks of young plants to prevent wind rock. These also have the added bonus of keeping the soil moist and acting to some extent as a mulch.
Where to buy: See proteapatch.co.nz for a large range of protea plants or good garden centres for a more limited selection. Photographic rights to these images and many others can be purchased from matthewsbotanicalimages.com