- Lighting – Full sun.
- Temperature – Being a warm weather plant, they must be provided winter protection. They can usually tolerate die back from a freeze, but will withhold blooms for awhile.
- Watering – Sparse to light watering and good drainage.
- Feeding – Fertilize once in the spring with a low nitrogen fertilizer and maybe once again in the fall. The old established method of forcing flowers is to withhold water to a point of causing severe stress to the plant. Research at the University of Florida has found that plants flower best when given high nitrogen fertilizers and short day lengths (15 hours of darkness within every 24-hour period).
- Pruning and wiring – The bougainvillea takes well to pruning; a useful attribute in styling bonsai. Because bougainvillea generally blooms on new growth, each branch, as blooms begin to fade, should be cut back to a point somewhat shorter than the desired length. Seal all cuts to prevent rot. If rot is detected on a collected specimen, cut it out completely
- Propagation – Bougainvillea may be grown from air layers, root cuttings and branch cuttings. Young shoots, a few inches in length, should be placed in sandy soil with bottom heat and moisture. Half-ripened or old wood cuttings in six to twelve inch lengths may be rooted April to June.
- Repotting – Repot in spring. Do not prune the roots too severely.
- Pests and diseases – Caterpillars, aphids, scale, greenfly and mineral deficiencies (chlorosis). Care must be taken that fungus does not invade the tree; reduced humidity and a preventive spraying of fungicide will help greatly.
Bougainvillea as Bonsai
Editor’s Note: This article was published in our June 2005 newsletter. Since then Lime Sulphur, mentioned near the end, is no longer recommended. The uniform whiteness looks unnatural and better preservatives are available now. We recommend PC Products, PC-Petrifier instead.
Bougainvillea can make a spectacular tropical Bonsai since they love to be pruned and will bloom in a pot.
Obtaining Plants: Large cuttings, up to four or six inches root easily. If the neighbor is having a monster pruned or removed collect some logs. Use about a two foot section and bury three or four inches. In warm weather these should root in six weeks or less, but wait a year to repot. A really avid Bonsai artist would drive around on Saturday afternoon looking for opportunities. Urban collecting can produce some nice trees. Bougainvillea gets too big really fast and a lot of homeowners have them removed. You will find these on the curb. Cut them back to a foot or less and pot them up in the largest pot you can handle. You will be surprised how many of these cuttings or collected plants survive.
The common red is more forgiving and the variegated leaf forms are the most difficult. If you visit nurseries you might find the dwarf Bougainvillea that has few if any thorns, smaller leaves, short internodes and avoids the rampant growth of the regular plant. The “dwarf” can get to twenty feet, but will still be more compact than the common variety. The down side of the dwarf is its limited color range. A named dwarf is “Pink Pixie.” “Pink Pixie” is interesting in that in low light the flowers are pink but in full sun they are red. “Pink Pixie” roots easily from cuttings but the plants might be harder to find. Pink Pixie leaves are borne more towards the end of the twigs with fewer side shoots.
Care Suggestions: Provide well draining soil and be careful not to over water. However, Bougainvillea seem to do better in peat/coir based soils rather than the traditional fast draining Bonsai soils. Repotting will be required every six months to a year. Prune a lot unless you want blooms. The Bougainvillea “flowers” are really modified leaves or “bracts.” The real flower is a small white thing in between the “bracts.” If you look carefully you will see the colored “bracts” as they develop and avoid pruning at that point. Watch your plants, if the leaves begin to droop, water.
Fertilizer: Bougainvillea doesn’t seem to be particular about fertilizer. A time release 14-14-14 works well as does a liquid for house plants if you only have a few plants. Follow package directions. A “bloombuster” with a high middle number isn’t needed.
Insects and disease: A common insect on the dwarf is a caterpillar that feeds at night. If leaf damage is seen look under leaves or in the soil at the base of the plant look for this culprit. Root rot and trunk rot are the biggest disease problems. Avoid root rot with good watering practices and use wood hardener on the trunk.
Styling: Bougainvillea can be wired but they grow so fast that clip and grow works well. If pruned heavily they will back bud abundantly. They are not going to easily fit a traditional Japanese style so it is best to use a free form style.
Warnings: Large cuttings and collected plants will all develop wood rot in the trunk very quickly. The best solution is to use this as a style feature. First use a high speed tool to carve the trunk and then paint it with a commercial wood hardener such as that made by MinWax. Multiple coats will be required as the wood hardener soaks in. The directions on the can are fine. Once the wood is stabilized it can be painted with lime sulfur to make the carvings stand out.
Bougainvillea are not cold hardy, that’s what “tropical” means. They will require frost/freeze protection. Plants in pots are more susceptible to cold than those in the ground. A Bougainvillea too large to move can be protected with a string or two of Christmas lights and a blanket or two.