Alocasia vs Colocasia

So what is the difference between Alocasia and Colocasia (apart from the spelling 😁)? This is one of the questions I wondered during my early years of collecting plants, and I must admit that I have interchanged both during some random discussions with other plantspeople. And while the matter has been resolved for me a long time ago, I totally understand the confusion it still brings to today's hobbyists. Unfortunately, the similarities are much more easily observed than their differences, which require scrutiny by a discerning eye, one which botanists commonly possess but not by most other mortals. Cheer up, lemme show you the way.

Above: Alocasia or Colocasia?

Really, you only have to take the time to look under the leaf surfaces of your plants. Alocasia have glands situated at the axils of the midrib and the primary (main) lateral veins. These are absent in Colocasia. The fruits of both also differ. In Alocasia, the berries are large and ripen to deep orange, whereas these are small and are in shades of green in Colocasia, and are also coated with slimy mucilage. However, you are much more likely to see berries in Alocasia than in Colocasia. In the Philippines, the introduced gabi (Colocasia esculenta) doesn't seem to be pollinated to allow the development of berries, and this appears to be true to many other regions where this food crop was brought. The native species, C. formosanum, does but these plants are confined to northern Luzon and are virtually absent in horticulture. Needless to say, the glands on the leaves' abaxial surfaces are the quickest way to decipher whether you have an Alocasia or a Colocasia.

Above and below: axillay glands on Alocasia sanderiana and an A. clypeolata x ? Such glands are on permanent vacation in Colocasia.

Below: Inflorescences on Colocasia and Alocasia. The inflorescences of Colocasia are numerous and are arranged around the stem, whilst it is on one side in Alocasia. If you still do not know what a 'petiole' is and insists on calling it a stem, believe me, the doors of heaven are locked for the mightily confused but are unaware of it.

Above: Colocasia esculenta 'Illustris'

Below: Alocasia sinuata

At this point, I should point out the very obvious: Very few Colocasia species are present in horticulture and the two that are most common are C. heterochroma and C. esculenta and its many cultivars (remember my apostle, the correct term is 'cultivar', not 'variety').* Among the cultivars of C. esculenta that are traded are 'Teacup', 'Illustris', 'Black Magic', 'Mojito', 'Red-eyed Gecko', 'Nancy's Revenge', 'White Lava', and many, many more. With only two species widespread in cultivation, you should have no trouble differentiating Colocasia from Alocasia- unless the cultivars confound you. The story might be different once we throw Caladium into the fray, though. But that is an entirely different story.

*The other 'Colocasia' sometimes seen in horticulture, Colocasia gigantea, is now under the genus Leucocasia.

POSTSCRIPT: This article is made upon request by my good buddy Jorge Sahagun.