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Bougainvillea

by Eugenie Sohnge

Louis Antoine de Bougainville (1729-1811), mathematician, soldier, scientist and navigator, sailed from France in December 1766. When he eventually reached the South West Pacific, like his predecessors, he turned northwards and missed discovering Australia but discovered the Solomon Islands in stead, the largest of which is named after him as is the plant, which grows so prolifically in the tropics and subtropics, the bougainvillea. He accomplished the first French circumnavigation of the word in 1769. He distinguished himself as a commander in the American war. After the outbreak of the French Revolution he returned to his estate in Normandy where he devoted himself to scientific pursuits. Napoleon made him senator, a count of the empire and a member of the Legion d'Honneur.

The genus Bougainvillea belongs to the tropical American family Nyctaginaceae (Gr. nyx, nyktos = night). Pukanawila, as it is known in Hawaii, is a woody vine which originated mainly in South America. When allowed to mature naturally, it may grow to 20ft in diameter. Because of its growth habit, with pruning it can be trained as hedges, shrubs or small trees. It has no fixed shape which makes it ideal to adapt to any design desired. The main attraction remains the colourful bracts or modified leaves. Flowering is influenced by sunlight, temperature and watering The bougainvillea's foremost attraction or focal point is its colourful blooms.

Flowers

The colourful "flower" of the plant is actually a set of modified leaves or a bract which consists of 3 coloured petals and the actual flower is the insignificant tube attached to the bottom of the vein which runs down the middle of the petal. The tubular flower has a frilly fringe and the stamens and pistil are inside the tube. Flowering is promoted by fertilizers with a high phosphoros (P) content ego superphosphate or 2-3-2. Plenty sunlight and not overwatering is important. Some of the best flowering plants grow in neglected areas, where roots are restricted, sunshine is plentiful and rainfall is minimal. I've seen some great specimens on farms along the road near the Kalahari Gemsbok Park. Bougainvillea is a tough survivor and thrives on neglect and abuse.

Leaves

Leaves are smooth-edged, alternate, oval or elongated and dark green. They reduce well after repeated pruning. Large leaves are an indication of over-watering or feeding.

Branches

The woody branches and especially the smaller branches are very brittle and break easily. The best method for shaping is by constant directional pruning. Wiring can be done in autumn for initial shaping, but take great care with the brittle branches and remove the wire after about two months.

Trunk

A well defined trunk is possible, especially with a field grown specimen. Nursery stock can be induced to thicken if planted in open ground and the trunk does become rough with age. However be careful when pruning larger branches, bougainvillea does not heal well, cuts must be smoothed and the edges protected with tree seal. Wiring the trunk when still in open ground must be checked weekly as growth is rapid.

Roots

The bougainvillea doesn't produce a massive root system, the roots are brittle and friable. It is not unusual for a clump of root-soil mass to fall off during repotting, but new roots are quickly generated; the plant will reestablish itself quickly from a drastically reduced root supply. Restricted roots are also not a problem and repotting is only necessary every three to five years.

Growing Medium

The soil mix must drain very well; bougainvillea don't like wet feet, they are prone to root rot. The soil mix should also be acid, so add about 20010 peat moss or add used coffee grounds. The soil mix should be appropriate for the local climate.

Propagation

Bougainvillea grows well from cuttings of about 6 - 10 em taken in summer. Air layering is also possible.

Maintenance

After the initial designing, growth can be controlled, to a degree, with the fertilizer used. Strong growth must be nipped to three or four leaves. After flowering prune back hard to keep the tree compact and to encourage new growth close in on the branches. Bougainvillea must have direct and full sun for compact growth, leaf reduction, branch ramification and flowering. Don't over-water, the plant it may lose its leaves, but don't assume that you don't need to water at all! Reduce watering at the end of summer and when the coloured bracts appear increase the amount of water slightly to promote and prolong the blooms. Repotting is also best done after flowering before the new buds open.

Fertilization

Overfertilization as with overwatering, can result in flower failure. During the growing season the emphasis is on growth and development. Use a high nitrogen fertilizer in spring like Nitrosol or 3-2-1 ~ a balanced fertilizer like 2-3-2 or a fish emulsion applied every two weeks in summer. Towards the end of summer give a boost with a high phosphoros (P) fertilizer like superphosphate to enhance flowering. In winter use a low nitrogen fertilizer like 2-3-4 or Chemicult about once a month.

Design or shape

Bougainvillea can be designed in most of the traditional styles except some obvious ones ego formal upright and maybe literati. The flowers are the most significant feature; the shape of the trunk and the branch formation become secondary since they will be obscured by the flowers most of the time. Bougainvillea is also a good subject for power-sculpting despite the soft wood. Cut paste should be used only on the edges of a cut face to prevent die-back. Large scars should be allowed to dry out completely to prevent rotting and then preserved with lime sulphur.

Containers

The container should complement the colour of the flowers. A deep shade of blue glaze goes well with the reds and purples; pastel shades like pink, yellow or lavender look best in a lighter blue, white or bone coloured container; rounded comers would suit the femininity of the flowers best. Containers should be medium to deep to uphold the 3-5 year repotting cycle.

Pests and diseases

Bougainvillea is reasonably hardy against disease. Well draining soil will prevent root rot. Fungus can be treated with a copper fungicide like Benlate. Insects like aphids, bugs, worms, beetles and moths should be treated with the appropriate insecticide. Malathion can cause defoliation, but it's not lethal.

Varieties

Bougainvillea glabra and Bougainvillea spectabilis are the most commonly used varieties. B. glabra is less thorny with large magenta bracts and B. spectabilis is thorny with small reddish-purple bracts. Considerable cross-breeding has produced hundreds of cultivars and these are often listed by colour (40 listed!). Some of the small compact varieties, which has naturally small leaves and flowers and virtually no thorns and doesn't grow very high, is called "Pink Pixie" alias "Torch Glow" and "Bangkok Red".

Our climate is ideal and Bougainvillea should be high on the list of desirable bonsai specimens; it is quick growing, a survivor and it gives us such a spectacular, colourful show.

Bibliography

Adam, Rudi. Bonsai in south Africa. Struik, 1992.

Chambers Biographical Dictionary. Sib edition, 1990.

Samson, Isabelle, The Creative Art of Bonsai.

World Tropical Bonsai Forum, Winter 1990; Spring 1990; Winter 1991; Summer 1992

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Random Bonsai Tip

Tying roots - Rubber rings (approx one centimeter thick) cut from a motor car tube, have many uses. For example use to tie roots in a Root over rock planting - they also make good garters!