Natal Plum Bonsai Tree Care Guide
Carissa macrocarpa (also known as C. Grandiflora) is a semitropical evergreen native to the South African province of KwaZulu/Natal. The full-size cultivars are often used as hedges, and may grow up to 20 feet in height in their natural habitat. There are several dwarf varieties, including one called Carissa macrocarpa 'Bonsai' which grows compactly to a height of just two feet.
This specimen is favored for bonsai due to its small, ovate, glossy green leaves (just 1-3" in length) which grow opposite along branches and twigs lined with 1-2" forked spines. The shrub produces star-shaped, waxy white flowers that are about two inches across and give off a sweet, orange blossom-like scent. The fruit, which often appears at the same time as blooms, is deep red, slightly pointed on the ends, and is edible – said to taste somewhat like cranberries. The bark fissures in a short time and becomes a light gray.
This subtropical evergreen should be protected in temperatures below 40° Fahrenheit. Ideally the tree will be kept in a warm climate with cooler nights, between 50 and 65°. Full sun will encourage blooming, although it can also withstand partial shade. If kept as an indoor plant Natal Plum should be placed in a south-facing window or supplemented with grow lights if necessary.
This species is drought-tolerant but should not be allowed to completely dry out. Good drainage is necessary to prevent root rot. Check the soil once or twice a day to make sure that it is not too dry.
Fertilize Natal Plum weekly with a good balanced feed administered at half strength. Supplement occasionally with high phosphorus fertilizer in order to encourage blooming. Chelated iron should be applied twice during the growing season or else chlorosis may occur. In late winter and early spring an application of micronutrients may be given.
Styles – C. Macrocarpa is best suited to informal upright or cascade.
Hard pruning should be performed in the spring after flowering occurs. Trimming all the foliage off of a branch may cause it to die back, other than back budding is vigorous. Trim new shoots with three to four sets of leaves back to one or two pairs as needed throughout the growing season.
This species is a fast grower so trimming is likely to be needed frequently to maintain your bonsai's shape. Rounded, shorter shoots are flowering shoots so watch for these if you want them to remain and produce blooms. Leave some, but remove a number of them as too much fruit production can stress a bonsai due to its miniature size.
Wire may be used on the trunk and lignified branches. Raffia should be used as protection on younger trees. Do not wire during blooming and be careful with older branches as they can be brittle. Rapidly growing plants need to be checked frequently to avoid cutting in of the wire.
Natal Plum may be propagated by seeds, air layering, grafting, or cuttings. Cuttings are best because they root easily. If taking softwood cuttings, place in moist sand and keep damp until rooting occurs, then transplant to a blend of two parts loam, one part sand, and one part peat moss.
For hardwood cuttings, apply rooting hormone and place in a glass of water. These cuttings set roots easily and can then be moved to an appropriate soil mix.
For younger trees, repotting should be carried out every year, with minimal root pruning performed at the same time. Older plants can go two years between repotting. Repot Natal Plum in autumn and winter. A well-draining bonsai soil should be used; this plant prefers alkaline, sandy soil so a mix of 50% potting soil, 25% Turface, and 25% coarse sand will work well.
Insects/Pests & Diseases
Although this is a hearty, resistant bonsai, it can fall prey to mealy bugs, spider mites, whitefly, aphids, and occasionally scale. Fungal infections may also present a problem.
Aphids, mites, and mealy bugs can usually be removed by spraying the plant off with water. Whitefly are persistent; these appear as tiny, snow-white insects that resemble moths. They are notoriously attracted by the presence of a Poinsettia. One recommended homemade insecticide is a mixture of two parts rubbing alcohol, five parts water, and a tablespoon of liquid dish soap. Spray this onto the foliage of the bonsai until runoff occurs, then spray with a rinse of plain water.
Fungal problems usually appear as black or grayish spots on foliage. Too much moisture, especially during the rainy season, can encourage these diseases to attack the plant. A mild fungicide may be used for most types of fungus.