Tannia

Tannia and taro are both called cocoyam, both are aroids, and both produce edible corms — and they are different genera from different continents with different disease profiles and different eating characteristics. In West Africa tannia is often distinguished as "new cocoyam" against taro's "old cocoyam". Any record naming only cocoyam has to be resolved before it means anything.

Fertilizer rates, timing, and forms should follow local soil tests and regional guidance. AgricultureID does not publish universal fertilizer recommendations.

Cocoyam root rot caused by Pythium myriotylum affects the vegetatively propagated commercial clones severely, and it has driven large declines in production in parts of Central and West Africa. Because planting material is corms carried from the previous crop, infected material moves the pathogen directly into new fields, and clean planting material schemes and tissue culture are the principal responses.

Management combines resistant varieties, rotation, monitoring, and — where justified — locally authorized control products applied according to their labels.

Tannia rarely flowers or sets seed in cultivation and is propagated from corms and cormels, so a farmer's planting material is part of the previous harvest. That ties planting rate to yield, means disease accumulates over cycles, and makes varietal improvement slow because there is no conventional seed system to move new material.

A single plant produces one central corm and a surrounding ring of smaller cormels. The cormels are the preferred food in most of the range, being finer-textured, while the central corm is coarser and is commonly used as planting material or processed. Harvest is by digging the whole stool, and some systems harvest cormels progressively and leave the plant standing.

As with other edible aroids, the tissues contain needle-shaped calcium oxalate crystals that cause irritation, and the crop is always cooked. Concentration varies by cultivar and by organ. This is a compositional characteristic of the crop; preparation and consumption guidance belongs to food sources.

Tannia tolerates shade and is widely grown under tree crops, in the humid forest zone and in mixed plots with plantain, maize and cassava rather than in monoculture. Its role in those systems is to produce a staple from ground that is already occupied.

The cormels are perishable and are attacked in store by a range of fungi, and post-harvest loss is a substantial share of the crop. Storage in the ground until required is common where the season allows, and it is more effective than any storage structure available at smallholder scale.

The crop needs high rainfall — figures around 1,800 millimetres a year are cited — and well-drained soil in a moderately acid range, and it does poorly on both dry and waterlogged ground. Root rot pressure rises sharply on poorly drained soils, so drainage is a disease decision as much as an agronomic one.

Soil suitability should be assessed with local soil survey information and, where available, field testing.

Tannia and taro are frequently aggregated as "taro" or "cocoyam" in international statistics, and much of the crop is grown for household consumption. Production figures for the species should be read as approximations built on that aggregation.