Cacao tree with pods and flowers.
Cacao fruit, the less common red pod form.

Cacao, also called Cocoa tree

Theobroma cacao

Origin:

Believed to be native to the upper Amazon regions, subsequently spread to meso-America and then from Columbian times elsewhere throughout the tropics.

Climate:

This species is an ultra-tropical adapted to lowland (less than 300m altitude) rainforests of meso-America ideally within 10 degrees north or south of the equator and which requires a moist environment. Temperatures under 20°C reduce growth, flowering, fruit yield and quality. Optimal growth is in areas with well-distributed annual rainfall of 1500-3000mm.

Plant Description:

It is a small understory tree, 4-8m high. Mature dark green leaves are simple, 15-40cm long.

Relatives:

Malvaceae Family. Relatives include kola nut and cupuassu. There are, in fact, a number of Theobroma species, some of which have the local name 'Mountain Cacao' and which grow at higher altitudes. This leads cocoa fanciers to hope that, somewhere, there are cultivars that are more cold-hardy than T. cacao.

Soils:

Soils should be fertile and deep.

Propagation:

Seeds are recalcitrant and viviparous. Seed pulp has to be removed for germination, and emerging seedlings need more than 50% shading for at least the first 6 months.

All vegetative means of propagation are possible but present various difficulties in use. Budding and grafting seem to be the most widely used currently in South East Asia and Brazil.

Cultivars:

Amazon cacao, which in the trade is called 'forestero' cacao, has purple-coloured seeds. Central American and some Venezuelan cacao, called 'criollo', has white seeds. Forestero trees are good producers, but criollo produces a better quality of chocolate. 'Trinitario' is a trade name for another class of cacao which is a cross between forestero and criollo. There has been some success in producing improved varieties through hybridisation and selection of disease-resistant clones.

Flowering and Pollination:

Inflorescences are cauliflorous, borne in leaf axil scars in small fascicles. Flowers are perfect with white petals.

Under optimal conditions trees may start flowering within 2 years. Cacao is morphologically and genetically self-incompatible and generally needs cross-pollination via midges. Self-pollination is more likely with cultivated than wild varieties and may occur via crawling insects such as ants and thrips.

Cultivation:

As any understory tree, a shaded location is preferred. Regarding fertilization, the largest macronutrient requirements are for N, K and Ca followed by Mg and P. Depending on soil fertility and pH, all the micronutrients may also need to be supplied regularly. Mature producing trees require more K than N (150%).

Wind Tolerance:

Trees are very sensitive to winds, resulting in defoliation.

Pruning:

Pruning of mature trees is mainly of two types: sanitary, to remove dead or diseased branches and structural, to limit height and keep the canopy open to sunlight.

The Fruit:

The ellipsoid fruit, smooth or ridged, weighs up to 300g and has a thick skin coloured green, yellow, red or purplish.

Fruit Production and Harvesting:

Mature trees can produce 50,000 flowers but fruit set may only be 1%. Fruit require 5-7 months to mature; harvesting is manual, staggered over a few months.

Fruit Uses:

The soft, sweet and edible white flesh surrounds 20-40 ovoid seeds which when dried and powdered are used to prepare cocoa and chocolate.

As well as the familiar forms of manufactured chocolate, the pulp can be eaten fresh or frozen and made into juices, jellies, ice cream and other sweets. It contains about 17% sugars.

Pests and Diseases:

With its preferred climate of hot, humid conditions, cacao suffers from heavy disease problems; pests less so. Each producing area of the world has its own specific diseases but Phytophthora (pod rot) is the most important disease worldwide.

Comments:

For those of you who like a real challenge, this one could be for you here in the South West of WA. Maintaining appropriate humidity, irrigation and minimum temperatures represent supreme obstacles to be overcome. Plus if you have a seedling, you have to hope it will be self-fertile!