Brazilian Rain Tree Care Guide
Chloroleucon tortum, also known as Pithecellobium tortum, is a tropical native of Central and South America. This tree, which grows in sandy soil, may reach a height of 15 feet or more. It is considered one of the most beautiful trees of the coastal rainforest and is listed as a critically endangered species. The Rain Tree is very much favored as a bonsai subject.
The deep green foliage of this legume is compound, with tiny little leaflets which make it attractive to bonsai enthusiasts. The leaves fold up at night, or when it appears dark during the day due to cloud coverage; they will sometimes even close up when it is simply too hot.
The trunk is fluted and exfoliating, with the brown bark peeling off in strips to reveal a light, smooth finish, resulting in a striking contrast between the two. The branches are home to very long, sharp thorns. The blooms are puffy white balls that turn yellowish with time. There may not be much flowering on a bonsai version of this plant due to the frequent pruning needed to maintain its size.
While the Rain Tree may be able to tolerate cooler temperatures, it should be protected in weather below 45° F. Exposure to cold may result in leaf and/or branch dieback. This bonsai is ideally an outdoor plant, although it can adapt to an indoor environment if given enough light (you may need to use artificial grow lights). If grown outdoors it should be brought in for the winter, and care needs to be taken with placing it in a window to avoid foliage burn from the magnification of the sun through the glass.
The Brazilian Rain Tree bonsai should be kept evenly moist. Do not allow the tree to dry out completely. This species also appreciates a humidity tray, in order to mimic its natural tropical environment.
Chloroleucon tortum is a heavy feeder. During the growing season, a balanced liquid mixture like 10-10-10 should be applied weekly. In the fall and winter once a month will do.
Styles – this specimen is typically seen as a formal or informal upright due to its tendency to grow straight when not exposed to the winds of its natural habitat.
Once the trunk and branch structure is in place it is generally best to use clip and grow. When pruning, leave a small nub in place to allow for potential dieback; some enthusiasts refrain from using concave cutters on the tree because of this tendency. This is a fast-growing species so weekly pruning is usually required during the growing season. Frequently trimming new growth will help in developing the foliage canopy for which the tree is known.
Because the Brazilian Rain Tree is a hardwood species, the trunk and branches are not easily manipulated once they lignify. Wire is not recommended. If training of the branches is desired, use nylon strips while the limbs are green and flexible. Only use wire loosely or to tie branches down.
C. tortum can be propagated by way of air layering or cuttings. For layering, cut a small ring of bark around the chosen branch. Leave the ends of the ring intact, as you will need a connection of the two halves of the branch in order for the tree to survive. Fill a small bag with moist peat and sphagnum and wrap around the cut area. Keep this bag moist for about 6-12 weeks and watch for root growth. You can take the cutting after is has developed enough of a root system to survive independently; cut just under the root ball and transplant into a pot, keeping the peat mixture in place around the roots.
This should be carried out every two or three years; make this judgement based upon whether the root system has become pot-bound (this species does not like being root bound). The roots can withstand moderate pruning. Repot in mid-summer – when night temperatures are no lower than the low to mid 60s F – into a well-draining soil mixture. Remember that the Brazilian Rain Tree grows in sand – if the soil is organic-matter heavy, it can cause moisture problems that allow root rot, fungus, and dieback.
Insects/Pests & Diseases
This species is quite resistant to most pests and disease, although it can be vulnerable to nematodes. These can be detected by the presence of root nodules that are integrated into the roots. Nematicide may be used in this case. Begin with a low dose and work upwards if necessary.
If kept as an indoor plant, check frequently for greenhouse pests like aphids, mites, and whitefly. Most pests can be washed off with a mixture of one teaspoon liquid dish detergent in a quart of water and sprayed till runoff occurs. Rinse with plain water.