Like most of the tropical fruits, cacao (the plant that gives us chocolate) is a novelty indoors. In its native environment, cacao thrives in very humid, but not necessarily very hot, sub-tropical and tropical conditions. It grows into a relatively small (about 20-25 feet) tree with deeply gnarled bark and a sometimes twisting trunk. The leaves are oblong and pale green and not especially spectacular.
What most people are interested in are the seed pods, which occur naturally on the trunk when the young trees are about four years old. The seeds are lobed and about the size of an adult hand. When you split open an oblong fruit, you'll find many oblong cacao seeds encased in a semi-gooey white flesh. The seeds, of course, are ground up into cacao powder, which is the basis for chocolate and many delicious things. Mature cacao pods are usually orange colored and take about 5 months to fully ripen on the tree. Whether or not you actually get cacao pods from your tree sort of depends on if you have a conservatory or not. There are mature, flowering cacao trees in conservatories throughout the northern United States, but for most home growers, they are strictly a novelty.
- Light: As a margin or understory plant, they do best with filtered sunlight. Cacao should not be exposed to direct, midday sunlight as it will scorch the leaves.
- Water: Regular water through the growing season and very high humidity (at least 70 percent). High humidity is the hardest condition to meet for these plants and the reason most home growers have trouble with them. I've read where some growers encase their plants in plastic bags to raise the humidity.
- Fertilizer: Feed weekly with a weak liquid fertilizer that includes micronutrients. They are heavy feeders, especially during the growing season.
- Soil: A light, fast-draining potting soil is perfect. Good drainage is very important for a health cacao plant.
Propagation is typically accomplished through seeds. The challenge for many people, of course, is to find viable cacao seeds. I've seen them for sale at plant fairs and expos, but they are also available online. If possible, it's better to buy a fresh pod as dried and older cacao seeds are usually not viable. Sometimes you'll find cacao seedlings for sale also. Seedlings should be exposed to less sun than the mature plant and can even thrive in shade for the first six months to a year. Once they begin to grow faster, move them into dappled sunlight.
Repot as necessary, preferably at the beginning of the growing season. When repotting, be careful not to disturb the roots more than necessary and give the plant plenty of water and humidity.
Theobroma cacao is one of the most important plants in cultivation today (especially if you happen to like chocolate). There are, however, other theobromas that are sometimes used.
Theobroma grandiflorum is used to produce the rainforest chocolate called cupulate, and according to Skyfield Tropical, some chocolate producers use Theobroma bicolor in their mix. Lastly, although T. cacao is the main species, growers all over the world have worked to specialize their trees based on microclimates and growing conditions (not unlike, say, cabernet grapes).
Cacao is not an especially easy plant. It can tolerate short periods of temperatures below about 60˚F, but it will not thrive and growth will almost stop. Prolonged periods of temperatures below 50˚F will prove fatal. It really does best when grown within its preferred, and relatively narrow, band of filtered sunlight, very high humidity, plenty of food and water, and warm temperatures. If you can provide these conditions, your plant should be fine.
Also, if you're set on getting seeds from your plant, you'll probably need two plants. Cacao flowers contain both male and female parts, but the vast majority of cacao plants cannot fertilize themselves, so a companion plant is required for germination. Most people who grow cacao indoors, though, aren't really looking for pod production and grow the plant as a novelty item and challenge. Cacao is vulnerable to mealybugs and aphids.