Carambola 261
14.6 Propagation.....................................................................................
The carambola is widely grown from seed though viability lasts only a few days.
Only plump, fully developed seed should be planted. In damp peat moss, they will
germinate in one week in summer, requiring 14 to 18 days in winter. The seedlings
are transplanted to containers of light sandy loam and held until time to set out. They
are very tender and need good care. Seedlings are highly variable and hence much
variability exists due to seed propagation. The seed derived tree takes 4–5 years for
flowering.
Carambola can also be propagated vegetatively. Veneer grafting during the time of
most active growth gives the best results. Healthy, year-old seedlings of 3/8–3/4 inch
diameter are best for rootstocks. Graft-wood should be taken from mature twigs on
which leaves are still present and, if possible, the buds are just beginning to grow.
Cleft-grafting of green budwood is also successful. Top-working of older trees has
been done by bark grafting. Air-layering has been practised and advocated though it
is less successful than grafting. The roots develop slowly, and percentage of success
often is low. Trees are small and rather weak when propagated by this method.
Usually vegetative propagation is resorted to only for the propagation of the sweet-
fruited varieties (Anon., 2001).
However, root formation is slow and later performance is not wholly satisfactory.
Inarching is successful in India, shield-budding in the Philippines and the Forkert
method in Java. Trees top-worked by bark-grafting is popular in Java. For mass
production, side-veneer grafting of mature, purplish wood, onto carambola seedlings
gives best results. The rootstocks should be at least one year old and 1–1.5 cm thick.
Grafted trees will fruit in ten months from the time of planting out. Mature trees can
be top-worked by bark-grafting.
Amin and Razzaque (1993) have successfully regenerated Averrhoa carambola
plants in vitro from callus cultures of seedling explants. Kantharajah et al. (1992)
have indicated roots as a source of explants for the successful micropropagation of
carambola (Averrhoa carambola L.). Multiple shoots were induced in Woody Plants
Medium or Murashige and Skoogs (MS) with 2 mg/l Benzyl adenine (BA) and 0.2
mg/l a-naphthalene acetic acid (NAA) with a multiplication rate of 2.1 shoots per
month. Adventitious shoot formation from fully grown cotyledon prior to maturity
was investigated. Explants produced callus and subsequently adventitious shoots on
MS medium supplemented with 4.4–13.2 mM BA and 0.54–2.7 mM NAA
(Khalekuzzaman et al., 1995). These shoots were rooted in half strength MS medium
with 2.46 mM Indole-3-butyric acid and established in soil. Plantlet regeneration
from hypocotyl explants of in vitro grown seedlings have been reported by Islam
et al. 1996).
14.7 Planting...........................................................................................
Carambolas do best in a frost-free location and the tree needs full sun. It prefers
warm humid areas, it can grow in most parts of the tropics and subtropics. Young
trees need protection from cold wind. Generally they are tolerant of wind except for
those that are hot and dry. A spacing of 6–9 m has been advocated depending on the
soil, giving more space in fertile soils.
At the Research Center in Homestead, Florida trees 8–10 ft high respond well to