Probably the most beautiful flowering bonsai, although the actual flower is small and insignificant, it is the colorful bracts that are spectacular, you can find them in almost any color.
Bougainvillea glabra and Bougainvillea spectabilis are the larger species where you can obtain some huge bases. They grow as a thorny sprawling climber. Bougainvillea ‘Pink Pixie’ has a more compact upright growth pattern with smaller leaves and flowers.
FLOWERS... The glabra and the spectabilis will bloom after being water stressed, withhold water almost to the wilt stage and then water. It is the spectabilis that you mostly see blooming after we have gone through a dry spell and then rains. Bougainvilleas bloom on new growth so defoliating the tree will force it to bloom and is much safer then water stressing it.
PRUNING... They can be heavily top and root pruned. The larger wounds are slow to heal and sometimes don’t heal at all. The wood is very porous and very susceptible to fungus and insect damage. You can use a wood hardener such as Miniwax wood hardener or Elmer’s wood stabilizer. I spray the wood with Lysol after working on it, especially if I did any carving on the tree. Even after all that it is hard to keep the wood from deteriorating over a long period, so you must keep up with applying the hardener.
TRAINING... You can wire for initial shape, the young greener branches bend quite easily but the older branches are very brittle. With the rapid growth of this tree, clip and grow is the best method for ramification and to reduce leaf size. Pinch off new leaves as they emerge. If the new leaves are getting a darker, brownish-red tint, stop pinching for it is going to bloom. Prune way back after flowering.
WATERING... Bougainvilleas need a very well draining soil. They like to be watered and then dry down. Staying too wet will promote more growth and less flowering, also will promote root and wood fungus. For growing out I keep them moderately moist in well draining soil. In a bonsai pot I tend to keep them on the drier side.
LIGHT... Full sun for best bloom and small leaf size. The Pink Pixie can take less light and still flower.
INSECT/DISEASE... Biggest problem is root fungus from over-watering. Aphids and scale can sometimes be found when there is always a lot of new growth.
FERTILIZE... Osmocote for a steady supply of nutrients and a twice monthly feeding of a balanced fertilizer such as 20-20-20 works well. Too much nitrogen will keep the tree from blooming.
REPOT... Minimum night temperatures of mid to high fifties. You can repot all summer. Bougainvilleas actually prefer to be a little root bound, it actually encourages blooming. Repot every two to three years.
SEASONAL... Protect below forty degrees.