Strelitzia reginae "Mandela's Gold" - A rare yellow form of the well-known crane flower, Strelitzia reginae. 'Mandela's Gold' is a stemless, evergreen clump-forming perennial. Greyish green, banana-like leaves grow to a height of about 1.5 m and during winter and spring the large bird-like flowers are held above the foliage on the tips of long, sturdy stalks. The structure and pollination of the flowers is fascinating. The hard, beak-like sheath from which the flower emerges, is called the spathe. This is held at right angles to the stem, and has the appearance of a bird's head. Each spathe contains 4 to 6 flowers, and these emerge one at a time from the spathe.
Each spathe contains 4 to 6 flowers, and these emerge one at a time from the spathe. Each flower consists of 3 clear yellow sepals and 3 deep purple petals. The yellow sepals give the appearance of a crest on the 'bird's' head. Two of the purple petals are joined together around the stamens and the style to form an arrow-like structure. The third purple petal is visible as a small scale.
Nectar is produced by a gland at the base of the flower. In fact, so much nectar is produced that it leaks out and drips down the side of the spathe. Although it is not certain exactly which bird is the pollinator, when it comes to feed on the nectar, it perches on the arrow-like purple petals, which open to expose the anthers and the sticky pollen adheres to the feet of the bird. The bird then transfers this pollen to the stigma of the next flower it visits.
Strelitzia reginae 'Mandela's Gold' is an easy plant to grow and will thrive in most soils. Ideal conditions are full sun, rich, well-drained loam soil with a pH of approximately 7.5, regular deep watering in summer and liberal applications of fertilizer in early summer. Bonemeal and plenty of mature compost should be mixed into the soil when planting. Plants will respond well to generous applications of manure and compost or additional fertilizer watered in about once a month during summer. A fertilizer with the proportions 3:1:5 encourages flowering, and can be alternated with other formulations.
In South Africa and other sunny countries, strelitzias will also do well in semi-shade, but in less sunny regions, they need as much sun as they can get if they are to flower well. Once established, they can survive with very little water, and they are tolerant of wind and coastal conditions. But 'Mandela's Gold' is sensitive to cold and needs a sheltered position against a north- or west-facing wall in areas that experience frost, and is not suitable for permanent outdoor cultivation in regions that experience a winter low of -7 to -1 ºC / 30 to 40 ºF (zone 9) or lower.
'Mandela's Gold' is a striking feature plant, a decorative garden subject and adds a tropical feel to courtyards and swimming pool areas. It is also an excellent cutflower. It is suitable for cultivation in large tubs and containers but for better flowering performance it should then be fed with a dilute liquid fertilizer at least every second week, particularly at the beginning of the growing season. In cold climates it can be grown in a sunny or brightly-lit conservatory.
Propagation is by seed or division. The plants are slow-growing and large clumps that are split or moved will take at least two years to re-establish themselves and flower again. To get a mature flowering plant from seed: under ideal conditions it takes about 3 years; but under less than ideal conditions it can take from 5 to 7 years. For best results sow fresh seed in spring or early summer. To improve germination, the seed can be soaked in a solution of ethrel, but this treatment is not necessary for germination to occur. Without ethrel treatment approx. 50% of the seed should germinate in 4 to 8 weeks with a further 30% germinating sporadically for up to one year after sowing. With ethrel treatment, 80% of the seeds should germinate within the first 4 to 8 weeks.
Before sowing, remove the bright orange aril and soak the seed in a solution of ethrel at a concentration of 2000 ppm active constituent, for 48 hours. Sow in seedtrays filled with a well-drained soil medium at a depth of 1 to 1½ times the size of the seed. A constant temperature of 25C is most suitable for germination as low temperatures retard germination. Seedlings should be a good size before being transplanted (two to three leaves) into a well-drained potting medium. In our nursery we have found that the young plants are best grown in semi-shade, as the leaves tend to burn in direct sunlight. Regular repotting allows the young plant to develop rapidly. Restricting the root development retards growth.
WINTER, JOHN. 1984. Going for gold. Veld & Flora 80: 22, 23.