OK I have been asked this alot and here goes my best example on how to ID your elephant ears. To keep it simple we are going to work on these three groups.
Colocasias are the most common. Sold as a food in Hawaii as Taro as well as all over the tropical word as a main food source. It has a thin leaf the tip points downward in all species EXCEPT Thialand Coffee cups is the first to have a tip point upward. A main point is that the back lobes are fused together meaning it has a heart shaped leaf rather than a arrow head leaf. So if IDing a colocasias first the tip points downward on the mature leaves. The leaves are not extremely thick but a bit thin. The back lobes are fused together to form a heart. Colocasias are a old world tropical so they believe. Meaning it is from Asia and surounding tropical islands.
OK now for Xanthosomas. This group can be a bit tricky even for botanist. Eduardo is a botanist in Brazil working on this group now and is the best at ID all species. Xanthosomas are new world tropical meaning it is from south america. It is closely related to syngonium this maybe why they always have white sap which syngoniums share the same trait. The leaves are usually very thin and the back lobes are NOT fused together. In the following picture you can see me holding a leaf. If you notice my finger is inbetween the back lobed area and the leaf is cut down to the stem. This is seen in all Xanthosomas. So what to look for in IDing a Xanthosoma the leaves are thin. The leaves do not point upward when mature but are horazontal to downward. The sap is white. The back lobes are not fused so if you look at the leaf head on you should be able to see the stem between the lobes.
Alocasias!! Well this group has one main constant the leaves are thick. The lobes can be fused or not fused. If the leaves point upward it is most likely a Alocasia though this is not true for all the species just some. It may take sometime but once around them you get a look and a feel for what is what. Hopefully these small tips can help. Their are bends and some breaking to the rules but in most cases it should help. I will add some photos of alocasias and other EEs to help see the differences.
This is alocasia Sarian thick leaf tips point upward. Its easy to ID as alocasia.
Colocasias are the most eaten Xanthosomas are eaten as well as are Cytrosperma Merkusii and I have heard of Macrorrhiza being eaten. But it is seldom seen as a food source. Black Magic Taro well it's a form of Colocasia esculenta. No one is sure exactly were it came from it could be a possible hybrid or a species or maybe just a mutated sucker off a regular taro. It has been around so long no one is for sure. But it does seem easy to seed which is uncommon in hybrids so it makes me wonder. Were your at Carol you should be able to find many Taro forms. The university of Hawaii has a Taro breeding program and a few other research labs are working on taros in that area. You should be able to find some interesting forms if you ask around.
I'm glad you're having great success with them, they add such a nice tropical look to gardens. Try some others too! There are colored stem colocasias and alocasias (although most alocasias can't take too much cold or water, but colocasias for the most part can)
Pink stems, red stems, purple stems...they're all very attractive, even if you grow them in large pots.
I've been looking throught a number of threads and I'm really confused by how many people list colocasias and alocasias as the same plant. I always thought and was taught that as you describe them the main difference is colocasia are heart shaped and point down in a more or less pendulum. Alocasia point up and are rigid. I have both. I used to have a colocasia frietek for instance, but most threads list it as a Alocasia. Its very confusing to say the least. I have a question that you might solve for me. I overwinter my tropicals in my greenhouse that maintains a heat level no lower then 45 degrees F. This has always worked well for me. My problem this year is the heat went off during subfreezing weather for about three days and completed froze and destroyed the leaves on the alocasias, I had to cut the stems off at the bulb leaving of course a open wound. I divided the plants repotted them, my question is should i completly cover the upper part of the bulb, or will they even come back. The Colocasias also suffered the same faith but I've just cleaned and packed them in bark to dry out and them I'll repot them. Any advice you can give would be appreiciated.
Mine had grown to about 5 feet high overwintering them in my living room. I accidentally left one out in a cold snap a couple of years ago; it hurt it a lot but now it is back up to about 4 feet. I didn't do anything with it; left it in the pot and kept it warm. It looked ugly for a long time but now it is doing good.
ID'ing Xanthosoma sagittifolium? A close look at all the pics on the Aroids forum of X. sagittifolium illustrated a structure on an un-ID'd ee I just received this fall. Think of the leaf as a capital "Y" with the ear lobes the top of the Y and the Y itself as the main leaf support structure. On these plants I have noticed that the leaf part of the lobes on the interior of the Y does not start growing from the Y join but starts a half inch or more from the Y join. My question to the experts: Is this feature one that identifies X. sagittifolium? Do I have a sagittifolium?
The pic shows a closeup of this feature, rather hard for me to describe. Note the V without foliage on the interior of the V which is the top of the Y discussed.
I'll get another leaf picture posted soon as the next one opens up. Only other leaf is damaged as trunk was cut back from shipping. Was told this one gets large, leaf is thin but dark green. Thanks for the info!
I have lots of photos of what I believe are Xanthosoma. Not sure what the species are though. Maybe you could help me. These were all photographed in Chiapas, MX. The really large ones are not eaten, whereas the smaller ones the leaves and tubers are eaten.
not sure if its true for all Colocasias but all the ones i have the water beads off the leafs, the whole water drop stays as a ball... where as the Alocasia's the water looks as it would on any plant leaf, it just runs off the leaf there is no water ball (not sure if that makes sense).. I dont own any Xanthosoma so not sure one those...
Which ever species of ears you have they are all a joy to grow...