Colocasia esculenta, Colocasia esculenta (L.) Schott, Exotic Rainforest rare tropical plants

Colocasia esculenta (L.) Schott
Before you stop at the first photo and say this isn't the plant you are seeking, scroll down! Colocasia esculenta has many faces. some quite large!

Colocasia species are known to be highly variable and not every leaf of every specimen will always appear the same. This link explains in greater detail the scientific principals of natural variation and morphogenesis. Click here.

Colocasia esculenta (L.) Schott

Synonyms:
Alocasia dussii, Alocasia illustris, Arum chinense, Arum colocasia, Arum colocasioides, Arum esculentum,
Arum nymphaeifolium, Arum peltatum, Caladium acre, Caladium colocasia, Caladium esculentum,
Caladium nymphaeaefolium, Caladium violaceum hort., Calla gaby, Colocasia acris, Colocasia antiquorum,
Colocasia antiquorum var. acris, Colocasia antiquorum var. aquatilis, Colocasia antiquorum var. esculenta,
Colocasia antiquorum var. euchlora, Colocasia antiquorum var. fontanesii, Colocasia antiquorum var. globulifera,
Colocasia antiquorum var. illustris, Colocasia antiquorum var. nymphaeifolia, Colocasia antiquorum var. typica,
Colocasia esculenta var. acris, Colocasia esculenta var. antiquorum, Colocasia esculenta var. aquatilis,
Colocasia esculenta var. euchlora, Colocasia esculenta var. fontanesii, Colocasia esculenta var. globulifera,
Colocasia esculenta var. illustris, Colocasia esculenta var. typica, Colocasia euchlora, Colocasia fontanesii,
Colocasia himalensis, Colocasia nymphaeifolia, Colocasia peregrina, Colocasia vulgaris

Common names:
Giant Elephant Ear, Elephant Ear, Black Magic, Taro, Wild Taro, Dasheen, Dachine, Black Taro, Dalo,
Eddo, Eddoe, Edda, Eddy Root, Green Taro, Coco Yam, Kalo, Callaloo, Poi, Katchu, Potato of the Tropics

Often incorrectly spelled Colocasia esculentum

An aroid species with many faces!

The chances are high you've at least admired this plant. Although I very much dislike the common name "Elephant Ear", Colocasia esculenta is sold and grown in many parts of North America using that overly used nomer. But it is known around the globe by a variety of names including Black Magic, Taro, Wild Taro, Black Taro, Dalo, Dasheen, Calaloo,Eddy and Potato of the Tropics. Why Potato of the Tropics? Because it is one of the most popular food sources in many tropical cultures! But few people realize Colocasia esculenta is not a single plant. It is a single species, but a plant with many "faces"!

Colocasia esculenta is a common aroid grown all over the world both as an ornamental plant and as a food source. Highly variable, the species can produce many leaf forms and sizes. The species is so variable it has acquired a long list of scientific names (see partial list of synonyms above). But there is only one basionym, a single base species name: Colocasia esculenta. As both an agricultural and an ornamental species, there are well over 200 known cultivars of Colocasia esculenta. Many are preferred for their edible corms (bulb) and leaves while others are grown strictly for their foliage. The species has so many variations that over 100 different forms are currently being grown in Hawaii alone. Hawaiian aroid, palm and cycad expert Leland Miyano explains about the significance of the species in his islands, "Kalo, in Hawaii, is considered a sacred plant. In fact, the Hawaiian people believe it is their ancestral older brother. The term for the keiki (propagules), literally children, is oha. Ohana means, "family". There are many such references to kalo in Hawaiian culture. In fact, there is so much written about kalo in Hawaii, that it is impossible to summarize in a short article. I can highly recommend a few books for those that want to learn more. NATIVE PLANTERS IN OLD HAWAII, THEIR LIFE, LORE, AND ENVIRONMENT. E.S. Craighill Handy and E.G. Handy. Bernice P. Bishop Museum Bulletin 233, Bishop Museum Press, Honolulu, Hawaii, Revised Edition, 1991; TARO VARIETIES IN HAWAII, Bulletin no. 84. L.D. Whitney, F.A.I. Bowers, M. Takahashi. CTAHR, University of Hawaii at Manoa, December 1939, Reprinted June 1997; TARO, MAUKA TO MAKAI. CTAHR, University of Hawaii at Manoa, 1997."

This link better explains natural variation which is a known scientific subject: Click here.

Despite all that has been written about the plant, as a result of all the known variations and the plant's ability to morph it is not well understood and is often the source of confusion among botanists, collectors, gardeners and growers. Jason Hernandez offers an explanation, "the problem is not just in the nursery trade! I have seen photos of Alocasia and Xanthosoma being used interchangeably even in what are supposed to be identification guides. In fact, I had to make note of this fact in both my Aroideana articles. In one of my sources, a photo of Xanthosoma was used to illustrate a species account of Schismatoglottis!"

Originating in the swampy regions of southeastern Asia, Colocasia esculenta has been cultivated as a food crop for thousands of years. On page 247 of Deni Bown's excellent book, Aroids Plants of the Arum Family, you'll find this passage, "The oldest cultivated crop in the world is an aroid: taro (Colocasia esculenta). It has been grown in parts of tropical and subtropical Asia for more than 10,000 years (Cable 1984). The ancient irrigation systems of terrace paddies seen today may well have been constructed originally for taro long before rice came on the scene, and rice may have first come to notice as a weed in the the flooded taro patches (Plucknett 1976)." Some sources indicate the species has long been grown in India as a food source as well.

If you look up the species on Floridata (a service of the State of Florida), you'll find this quote, "Colocasia esculenta, wild taro, is an invasive exotic in much of peninsular Florida. It is listed by the Florida Exotic Pest Plant Council as a Category I Species, known to be disrupting native plant communities and displacing native plant species. Taro forms dense stands along lakes and rivers where it completely eliminates native plant species. Taro should not be cultivated outdoors in the vicinity of wetlands where it could escape and establish a self sustaining population that would eliminate native species." The species is considered an invasive species in the State of Florida.

So why do I dislike the common name "Elephant Ear"? Simply because people use it for almost any plant that has a large leaf. It no longer matters if the leaf is stiff and leathery (coriacious) or floppy. If it is big, people call the plant an "Elephant Ear"! If you visit any garden discussion website you'll find people asking questions about "Elephant Ear" Colocasia esculenta, Elephant Ear

plants without regard to the species. And those plants may be one of several thousand species! Members of the genera Alocasia, Colocasia, Anthurium, Philodendron, Caladium, Monstera, and Xanthosoma have all been called "Elephant Ears". If you study plants you'll soon learn those seven genera contain over 3000 species! So if someone asks for advice how to grow an "Elephant Ear", which one of those thousands of plant species are they asking about? Some species love sun. Some love shade. Some love water. Some will die in water. Some will grow dry. Some are epiphytes and grow up in the trees! It would take a very good mind reader to instantly be able to give accurate advice without seeing the plant. And most of the time, when people ask about an "Elephant Ear", they do not post a photograph! As you'll learn, even seeing the actual specimen is no guarantee you'll quickly be able to discern the species! But there are those who love to defend the use of the name for any plant with a large leaf.

Although vaguely descriptive, as a common name, "Elephant Ear" is a near useless term. Grower Brian Williams tells a good story about the very vague common name, "Usually most uneducated people on aroids will call anything with this type of leaf an Elephant ear. I don't like it so I try to educate them about the plants. One guy came into the nursery and we were surrounded by Colocasia and Alocasia on the path and he asked me if I grew any Elephant ears. My answer was a absolutely not! I then told him of the different forms and how they all seem to be called Elephant ears." Standing in the center of a large group of specimens that are often called "Elephant Ear" plants, the gentleman had no idea what he was asking about!

Colocasia esculenta is an aroid and a stately Alocasia relative that is extremely variable. But it is not an Alocasia even though botanists have tried to place it in that genus! Variability is a term that is well known among aroid botanists and serious plant growers. In the simplest terms, a variable species is one that may present many shapes or "faces". Impossible you say? Well, the scientific fact is variability is both well known and common. Variability is best known within the larger plant family known as Araceae which contains all aroid species. Colocasia esculenta can present leaves that are very large or relatively small. The leaf color can be green, deep black, slightly purple or even blue/black. The blade shape can be sagittate (arrow shaped) or more ovate. And as you can see from the long list above, Colocasia esculenta has managed to fool a large number of botanical scientists! Variation within the species has been misunderstood for many years.

This species has at least 68 synonym scientific names. A synonym is a scientific name which has been used to describe another species already known to science, i.e.: same species, other name. However, in science, the first name given to the species that is found accurate to the correct genus becomes the basionym. And in this case, that basionym is Colocasia esculenta. Although many botanists have thought (incorrectly) this species was a Caladium, scientifically it is a member of the genus Colocasia. You can find several websites that incorrectly claim all large Colocasia esculenta, Elephant Ear

"Elephant Ear" plants are Caladium or Alocasia species. If you examine the long list of synonyms at the top of this page, you'll find this plant has in the past been considered by scientists (in error) to be a Caladium, an Alocasia and an Arum. Aroid expert Julius Boos offers an explanation about Caladium species as an Elephant Ear plant, "The two largest plants I know of are Caladium bicolor var. The Thing which has a spotted leaf with red and white on green. It might have a blade 24" long by 18" wide. The other is what is presently being called in error C. bicolor 'rubicundum which is about as large but with a wider more rounded leaf and translucent purple/lilac spots on a purplish-green leaf. It is being worked on by Josef Bogner and Willbert Hetterschied at the moment. None are plain green, and I have never heard them referred to as Elephant ears. None which I have seen sold as Elephant ears have been Caladium. They are either Colocasia or Xanthosoma." A leaf blade 24 inches by 18 inches would measure approximately 60 x 45cm.

One of our favorite forms of Colocasia esculenta, known to many as Black Magic (photo left), can easily produce black, green or even blue/black leaves within the same plant group! In a single season it often loses the dark black leaves and simply turns green. The larger variations of this plant species found in Florida and tropical regions grow from a corm which you likely have called a "bulb". And many of the "bulb" type plants are the ones you buy at major nursery centers and department stores as the giant "Elephant Ear". But in most cases they are just a form of Colocasia esculenta.

Colocasia esculenta was first identified to science in 1832 but due to the species' ability to produce so many variable forms it has managed to confuse botanical scientists for almost 180 years. As a result, many botanists thought they were investigating a new species which later turned out to be one already known to science. Colocasia esculenta not only takes on many leaf forms, it can actually change its appearance in a single season.

Although a few species of Alocasia and Xanthosoma are also sold in discount centers and nurseries using the common name "Elephant Ear", many of the plants you buy in the spring with that common name are nothing more than Colocasia esculenta. Aroid grower Brian Williams of Brian's Botanicals (http://www.BriansBotanicals.net/) explains, "I find that just about all plants labeled commercially as Elephant ear are Colocasia esculenta. The Xanthosoma sp. are a bit harder to find and I have rarely seen them commercially available. Yet many times I have seen photos of Xanthosoma sp. being used to sell Colocasia as well as Alocasia. Caladium sp. are usually marked a bit better. The Colocasia in question though is very interesting. It maybe a tetraploid, possibly a triploid, as it grows much larger and very rarely produces flowers. I have only seen flowers one time. The tubers can grow extremely large, 1 foot long or more and 6 to 8 inches across. I have seen a few photos of the plant grown to 10 feet tall or more. I am not sure if this form is used in any taro production, it would be interesting to find more on it's origins. I have some good photos of one around 8 feet tall." A tetraploid has four times the haploid number of chromosomes and a triploid has three times the haploid number of chromosomes in the plant's cell nucleus. As a result, it grows larger.

Brian continues, "The large rounded tubers commonly sold are almost always Colocasia esculenta. In most cases the Xanthosoma are elongated and usually have pink colorations in or on the tubers. I have rarely seen Xanthosoma sold commercially, but more often they are sold as food in ethnic stores as Malanga. Colocasia is usually sold as Taro or Dalo. One of the best ways to tell if it is a Xanthosoma is to see the color of the sap. Xanthosoma usually have white sap along with pink to white spathes. There is only one Colocasia I know of with a white spathe and that is Colocasia gigantea." Scientifically, those tubers are known as corms, not bulbs.

As a result of Brian's comments, a further explanation of aroid species is in order. Within aroids, and many other plant families, botanists do not determine the species by the shape of the leaf. Instead, the final determination is made by microscopically examining the sexual portions of the plant's inflorescence known in aroids as the spathe and spadix. But to complicate matters, even the spathe and spadix of Colocasia esculenta (and other species) can be variable! It is not uncommon for the spathe of one specimen to be a different color when compared to that of another specimen of the same species. Even the shape of the spathe can be variable.

When I asked botanist Alistair Hay about the differences in both color and shape of the spathe of different specimens of Colocasia esculenta he responded, "What you seem to be wrestling with is the general concept of a species. This is extremely difficult and there have long been widely different views about what species are! An evolutionary definition is that it is a unique lineage, and that lineage may or may not embody great variation. There is no in-principle reason why any feature, be it inflorescence or leaves or pollen grains etc, shouldn't be variable within a species. What one first looks for in defining where a species begins and ends in relation to other species is breaks in variation which one thinks are significant. To take your pic, a different colored spathe may not be significant in defining a species, unless correlated with breaks in variation of other feature(s) as well. It is just a color form of the same thing ." Sound complicated? Well, to those who believe that every leaf of any species must be identical to those of all others within the same species, it is! But to a botanist who has studied and understands the concept of plant variability, it is simply a natural part of botany. Plants vary a great deal within the same species just as humans vary within our own species. Just because humans don't all have identical faces, have different color skin, different color hair, as well as some are short and some are tall, does not mean we are different species. Plants are the same. Colocasia esculenta is known to freely morph and can change its appearance in just a single season. The photo of the yellow/red spathe above is of the Black Magic variation seen at the top of the page and does not necessarily resemble the spathe and spadix of other variations shown on this page.

The major parts of an aroid's inflorescence are known as the spathe and spadix. If you've ever grown a Peace Lily (Spathiphyllum), you've seen one. But the chances are you called that beautiful white growth a "flower". It is not! Instead, the spathe is simply a specially modified leaf produced as a part of the plant's reproductive process. The true flowers are very small and are found along the spadix at spathe's center. Those flowers include different sexes, both male and female. The male flowers produce pollen and the female flowers may be receptive to that pollen. However, in some aroid species the female flowers are not receptive to the male flowers from the same specimen. As a result, an insect is required to transfer pollen from one plant to another. When an insect travels up the length of the spadix and gathers the pollen grains on its legs and body it carries that pollen to the female flowers of either the same inflorescence or another specimen of the same species. Nature has designed a very unique method to cause insects to move pollen only to plants of the same, or a very similar species. During the reproductive cycle the spadix emits a pheromone which to the male insect of the species is identical to the "perfume" produced by the female of his own species when she is ready to mate. As a result, the male of that "assigned" insect species is deceived into landing on the spadix of a plant species where he gathers pollen and then carries it to another spadix of a receptive specimen. The plant is then pollinated and eventually seeds are produced. In the case of aroids, the seeds are found in colorful and unique berries that are often eaten by birds and dispersed throughout the forest. Nature has again succeeded in assuring the continuation of the species.

The plant may also reproduce by producing additional corms (sometimes known as mammies) beneath the soil or by sending off long runners called stolens which attempt to root in the soil or in any nearby body of water. Colocasia esculenta is naturally drawn to bodies of water and is frequently found growing in and along the edges of streams and ponds.

Almost all specimens of Colocasia esculenta also love to reach for the sun and will tend to grow from shady areas towards areas of brighter light. However, many variations grow very well in slightly diffused or even shady light zones. Colocasia esculenta is frequently found growing in direct sunlight but may grow slightly taller in light shade as it stretches for the light.

On many tropical islands, as well as in South America and Asia, the leaves, stems, corm and roots are all boiled and eaten. The leaves are cooked like spinach or other "greens" and used to wrap pork and chicken while it is being cooked in a fire pit. Although not all, many variations grow a large corm which is also eaten. The species is commonly grown as a food source in virtually all the Caribbean, Central America, South America, Polynesia, and SE Asia. In Polynesia the food form is known as "poi", in Hawaii as Kalo, while in the Caribbean it is more commonly known as dasheen. During the late 1970's we lived on the island of Jamaica and a favorite food on that island is Callaloo. Although I knew Callaloo was a vegetable I did not know until I researched this article the Jamaican delicacy is truly Colocasia esculenta.

Despite the fact you'll find many websites claiming the species is "deadly poisonous", this species is commonly eaten as a staple food source. In South Florida you can find the corms sold in the vegetable aisle of almost any major food store. The leaves, roots and stalks are all consumed and cooking apparently has only minimal to do with the ability to eat the species other than flavor. Known by many names the species is obviously not the "deadly poison" many would have you believe! However, eating a specimen raw can be very distasteful as well as uncomfortable to the throat and mouth. Even the garden form shown at the top of the page (Black Magic) is used as a food source. If you have been to Hawaii and enjoyed a luau or vacationed on any island in the southeastern Caribbean you have almost certainly eaten the plant! Since Hawaiians eat Kalo, a local name for Colocasia esculenta, this explanation from Leland Miyano, who was born and raised in Hawaii may help, "Kalo cultivation varies according to types. There are two basic groups; Dryland kalo and Wetland alo...self-explanatory. Wetland kalo requires fresh, flowing, cool water for best performance. There are so many details, but in old Hawaii, the cultivation of kalo was raised to a high art."

All forms of Colocasia esculenta contain calcium oxalate crystals just like all other aroid genera including Philodendron. If you read many child care and pet sites on the internet you'll often find this plant product is claimed to be a "deadly poison". It is possible for calcium oxalate crystals to burn your lips and throat but someone better explain that it is a "deadly poison" to the people of the Caribbean, South America, Central America, Hawaii, Polynesia and Asia since they eat it daily! Scientific sources say cooking has nothing to do with destroying the "poison". (Read our detailed explanation with scientific references from the link below this article.) Leland explains further, "Kalo has two types of calcium oxalate crystals, or idioblasts,....needle-like raphides and club-like druses. It is believed that the raphides cause the mucous membrane irritations and skin dermatitis. I can speak from personal experience that eating raw kalo, leaves or corms, is not recommended. It is as if one ate fiberglass. Another warning is Agave species have these raphides and I can attest to the extreme skin dermatitis from the sap of these...it manifests in intense itching and burning...it is a torture, that can last for many days in some people. In short, although spinach has calcium oxalate crystals, there is no comparison between them. I eat raw spinach often, but raw kalo, never. Cooked kalo is one of my favorite foods, both leaves and corms. Poi is the mashed corm and is delicious in my mind. It has been compared to library paste but some luaus cut their poi with flour and it does taste bad. The variety of kalo also determines the taste."

Although I don't recommend you go around chewing on Philodendron and other aroid leaves (they often taste bad) I suspect it is more a matter of an acquired taste as Leland suggested. However, some people do react badly to the compound. One genus within the aroid family, Dieffenbachia, is especially notorious at being potentially harmful and can easily cause the loss of the use of your vocal cords. In a very few cases, consumption of Dieffenbachia has proven fatal. But if you've ever eaten spinach, you've already eaten calcium oxalate crystals. Some people don't like spinach and the main reason is likely the vegetable contains one form of those crystals in a very high quantity. To some, vegetables containing calcium oxalate crystals has a pungent flavor! But people eat spinach raw in salads all the time and do not die. Still, eating any aroid raw without the proper knowledge how to prepare it is not advisable. Leland continues, "I do not think is is a matter of taste...it is a physical reaction that has to do with the structure of the dioblasts...needle-like raphides versus the club-like druses. I do not know about spinach idioblasts so I can only comment on kalo. It is not the taste of raw kalo that is disagreeable, it is the irritation of the throat and mouth that would prevent a second sampling. Calcium oxalate is not a poison...but the raphide form is certainly a deterrent to ingestion. I do not know of anyone dying from raphides, but if the dermatitis from Agave is any indication, if one were to eat raw Agave in copius amounts, I would imagine a very bad experience. I also believe the variety and age and perhaps other variables determines the amounts of the raphides in kalo."

Colocasia esculenta can be grown not only in the semi-tropical parts of the United States but also in many cold areas although it will go dormant during winter months. It has been reported to grow again after a frost or even light snow in Japan. Many growers have reported excellent results leaving the plant in the ground all winter including here in NW Arkansas. For best growth, we recommend a good mix of potting soil along with peat and Perlite™ to create an artificial "bog" that holds moisture. For ideal growth, the species prefers a slightly acidic soil and should be kept well watered.

I often am asked how I get the plants to appear "blue". I really don't know. Not every photo and specimen has the blue cast. Sometimes they are green, sometimes black, but they do sometimes show the beautiful blue cast. Since the species changes color as it grows (beginning normally as green) I suspect it has something to do with the plant's age, light conditions, fertilizer and possibly the soil pH. Plant coloration can be a result of a botanical phenomenon known as anthocyanins, a condition where water soluble pigments appear red to blue depending on the soil pH.

If you still find it difficult to understand how a single species can be so variable and present so many "faces", you are not alone. Jonathan Ertelt of Vanderbilt University in Nashville, TN sent one of the best possible summations of the difficult concept of variability, "When you think about it, in other genera within our own family here (speaking of Araceae of course), the size or texture of a leaf blade, appearance of the venation, or cross-section of petiole showing different shapes can make the difference between species. But if my understanding is correct here, this species concept is plastic enough that leaf size, surface, appearance of venation, (i.e. raised and rounded or angled, or flat), petiole appearance, position of inflorescence, shape, size, color of inflorescence, and of course habitat and resulting vegetative growth, and likely pollinator differences as well between habitat extremes of wet and dry - none of these things matter with this species. A most interesting dilemma - it is no wonder that it has so many synonyms, both scientific and common. When all the usual species defining characteristics are thrown out, where do we go? With such incredibly wide degrees of variation, whether one is using the common name or the botanical, another could still have no earthly idea of the image of plant being discussed. An interesting dilemma indeed."

After reviewing this page, America's top aroid botanist Dr. Tom Croat of the Missouri Botanical Garden in St. Louis offered this opinion, "I quickly read through your page on Colocasia esculenta and found it very useful and thoughtful. Certainly those elements that you have there represent what falls in the parameters of C. esculenta but I am no expert on this Asian genus. I have never seen the very large plants grown by Brian Williams. They would appear to be twice as large as any plant I have seen anywhere in cultivation. Perhaps he is correct that it represents a tetraploid form. At least one of the two smaller forms are what has been called Colocasia esculenta var. antiquorum. Check the pictures in Exotica."

You may find the name incorrectly spelled as Colocasia esculentum on many "scientific" and pseudo-scientific sites. That is likely due to someone mixing an older scientific name (Caladium esculentum) with the correct name. However, if you go to a scientific database, you wil not find the spelling "Colocasia esculentum". Check TROPICOS (Missouri Botanical Garden) http://mobot.mobot.org/W3T/Search/vast.html or the International Plant Names Index (IPNI)

http://www.ipni.org/index.html to verify the correct scientific spelling which is Colocasia esculenta.

My thanks to Brian Williams for his input and the use of his photographs. (http://www.BriansBotanicals.net/) and to botanist Alistair Hay for his assistance as well as to Dr. Croat, Julius Boos, Leland Miyano and Russ Hammer for their assiatance as well as checking the accuracy of the information on this page.

Click these links to see two other specimens commonly called "Elephant Ear":
Alocasia odora

Xanthosoma sagittifolium

Want to know more about calcium oxalate crystals? Chances are, you've eaten it in the past week! Click here:

http://www.exoticrainforest.com/Calcium%20oxalate%20crystals.html

Join the International Aroid Society: http://www.exoticrainforest.com/Join%20IAS.html