Big, Beautiful, and Edible too!
What could be more perfect for your tropical garden than a plant that looks exotic, has large leaves, and can serve as a tasty addition to your dinner table as well? Well, members of two aroid genera, Colocasia and Xanthosoma can do just that for you. In fact, obtaining these plants can be as easy as visiting your nearest ethnic grocery store and looking for tubers labeled "malanga" or "taro". "Malanga" is the produce name for the edible Xanthosoma, and "Taro", the name for Colocasia esculenta. Once you have some of these, you can grow your own both for gardening enjoyment and for culinary satisfaction!
Unlike Alocasia, these two genera have members that hold their leaves generally perpendicular, or at right angles, to the petioles supporting them. Leaves on Colocasia are more rounded (see thumbnail picture above, right), while Xanthosoma leaves are more sagittate, or arrowhead-shaped (see picture below, left). Leaves on plants in both genera are typically softer than those of Alocasia, and they have a matte look to the surface. Contrast this with the large Alocasia species, in which the leaf surfaces are somewhat to very shiny.
Don't eat them all!
If you obtain your starts from the grocery store, you can be confident that they are the edible varieties, but if you scout around, especially in Florida, you may find some non-edible types growing in gardens. So you should not assume that the specimen you obtained in a swap is one of the edible ones! I have seen fields of both edible kinds growing in south Florida, however. These two kinds are not the giant-growing kinds that most people might see in tropical landscapes.
I've seen one species of Colocasia growing wild in wet swales near where I live; this plant grows by runners and grows only to a height of 2 to 3 feet. It blooms with yellow inflorescences that smell somewhat like ripe papaya, and seems to thrive well in a swampy environment. Several ornamental varieties of Colocasia, such as the variety 'Black Magic', also propagate by runners and have yellow or yellowish blooms. Other desirable varieties have red, pink or purple petioles and variously colored splotched leaves. The one that takes the "Big Ear" award for the genus is Colocasia gigantea, which in size can rival some of the largest Alocasia specimens. However, if you intend to try growing this behemoth, make sure you have it in an area protected from strong winds, as such winds will tear up the relatively delicate large leaves.
Easy to keep!
The edible Colocasia and Xanthosoma are relatively easy to grow and store. They should be cultivated in good garden loam with plenty of organic matter, such as well-aged compost or composted cow manure, mixed into the soil, and they should be kept amply watered. If you intend to eat some of the corms when you dig them up in the Fall, I recommend refraining from the use of any chemical pesticides in or near them.
Personally, I find that malanga makes a superior "mashed potato", having quite a bit more flavor than that well-known member of the Solanaceae. They should be skinned and cooked much as you would cook potatoes, then can be added to vegetable soup or eaten buttered as a tasty vegetable by themselves. I haven't yet experienced Colocasia as part of my dinner menu, but I understand that Taro is a staple in Hawaiian cooking.
All in all, you may well discover that you can have your tropical garden and eat it too! Bon Appétit!