A king protea is a woody shrub that is native to South Africa. It is also the national flower of South Africa. Of all the different species of protea, the king protea has the largest flowers, measuring between 6 inches (15 cm) and 1 foot (30 cm). What appear to be flowers are actually brightly colored, petal-like leaves called bracts that contain clusters of true flowers, which are usually duller in color. The bracts are usually considered the flowers on all the protea species.
Grown commercially in New Zealand, South Africa and Hawaii, the large, bright, dramatic flowers of the king protea are popular as cut flowers for use in bridal bouquets and large floral displays. The mature plants make a spectacular addition to large gardens or as a striking landscape feature. King proteas are slow-spreading plants that can reach more than 6 feet (2 m) in height and width.
There are approximately 80 varieties or cultivars of the king protea species. Because the plant has such a huge native range, it has evolved and adapted to differing environmental influences in different locations. These locally adapted cultivars have resulted in a wider variety of flowers, ranging from bright white through shades of pale pink to deep crimson or red.
King protea cultivars have also evolved with different disease and pest resistances, different plant and flower size and different soil and water preferences. The wide range of available cultivars can be found growing from sea level to altitudes above 4,920 feet (1,500 m) above sea level. While some king protea varieties will tolerate heavy soils, no variety will tolerate long periods of waterlogging, and all varieties prefer light, well-draining or sandy soils.
A useful plant for landscaping in areas with poorly conditioned soil containing few nutrients, the king protea has a large, elaborate root system that allows the plant to gather resources from a wide area. King proteas will not tolerate temperatures below 59° Fahrenheit (15° Celsius), but in cooler climates can be grown in containers so the plant can be moved inside during colder months. In containers, the king protea can also be grown as a house plant.
In small gardens or as a house plant, the king protea will most likely need to be vigorously pruned to keep it at a manageable size. King proteas can be fertilized, but this species does not tolerate phosphorous, so a low-phosphorous fertilizer must be used. Most cultivars are prone to magnesium deficiency, which results in poor health, reduced flower production and even death, so — especially in containers — it may be necessary to add magnesium in the form of fertilizer.