Wild, Wonderful Aroids Part Two - Elephant Ears, Alocasia, Colocasia and Xanthosoma
Author: Marge TaltPublished on: Oct 21, 2002
Part Two - Elephant Ears - Alocasia, Colocasia & Xanthosoma
While caladiums are sometimes called 'elephant ears', to me the real elephant ears are the huge plants that belong to three genera: Alocasia, Colocasia and Xanthosoma. These are the plants that can (under ideal conditions) reach five to nine feet (1.52 - 2.74m) tall with leaves that can be up to three feet long and across (.9 x .9 m). Under really ideal, tropical, conditions, some can get larger than that, but most of us won't be able to provide this for them.
Many species of all of these genera are edible with proper preparation. They have been staples of diet for people in the tropics for thousands of years. Hawaiian poi is made from these plants. All of them contain crystals of calcium oxalate, which disappear with cooking. Proper preparation is essential because in their raw state they can cause severe discomfort if eaten. While the corm or tuber is the main part used for food, young leaves can also be prepared and eaten; some species are grown specifically for their edible leaves. All of them are grown in gardens for their fabulous foliage. If you yearn for a touch of the tropics in your garden, you need an elephant ear or three.
Of these three genera, the only one I am growing at present is Colocasia. This error will be corrected next spring because I have recently discovered plants in the other two genera that I simply have to have.
Colocasia
There are about fifty-eight species of Colocasia listed in W3TROPICOS, two with extensive variety lists. Of these, I grow only two forms of Colocasia esculenta, which has some twelve varieties listed on W3TROPICOS. In addition to elephant ear, Colocasia is commonly known as taro, dasheen, cocoyam, Kalo, malanga, Taro de chine and Chinese potato - as, I might add, are species of the other two genera. The common names are not the way to try to identify an elephant ear.
My first Colocasia was given me by a friend who got it as a tuber at the grocery store. It's the one with the huge green leaves in this photo, in a strange, but interesting, combination with Euphorbia characias.
They look like they are planted together, but, in reality, the Euphorbia is in a bed about two feet (.6 m) higher than the mud hole in which the colocasias grow.
I say strange because these two genera require diametrical growing conditions; one requiring sharp drainage and the other liking and even growing in water. One comes from Mediterranean climes and the other is tropical. Normally, I would not consider these as companions, but the juxtaposition of the sharply different foliage shapes and colors has pleased me all season.
Several synonyms for Colocasia esculenta
|
Confusion seems rife on the net regarding the different types of Colocasia esculenta. Even according to various aroid gurus on Aroid-L, there is some disagreement. As nearly as I can determine, there are three main types:
- The dasheen type (or araimo in Hawaii), which, in the US, have one large oval or trunk-like central rhizome/tuber/corm (it's referred to by all three names in various references). there are several varieties with different colors, flavors and textures; some with white-fleshed oval tubers, others with gray/blue fleshed tubers. The leaves generally have a dark spot in the center, lacking in the eddoe forms. All are varieties of Colocasia esculenta esculenta. In Hawaii, where most dasheen taro was introduced from Asia, the dasheen refers to varieties that produce small corms (smaller than fist sized) and send out runners.
- The eddoe type, who produce many small, oval tubers/corms from the central, slim underground portion of the rhizome. There are at least two types of these, either C. esculenta var. antiquorum or C. esculenta var. globulifera.
- The third type produces many stolons but only small or no tubers/corms. It occurs in many forms with many leaf colors and is used for leaves that are cooked and eaten similar to spinach and for "wraps". Some of these contain less crystals of oxalate in their leaves than others. It appears that there are many names for this type, but they may not have any scientific standing. Some now grow as invasive weeds in Florida.
There are literally countless varieties or forms of Colocasia throughout the tropics. In Hawaii, there are over three hundred names for taro varieties, but many are local terms for single cultivars. I have read that it is also generally accepted that there were easily over a hundred varieties in the past since Hawaii cultivated taro more than most Polynesian cultures.
Even given the above, a post I saved from Aroid-L stated:
"Dan Nicolson (Flora Vitiensis Nova 1, 1979) and I (Sandakania 7, 1996) came to the conclusion that subspecies and botanical varieties of Colocasia esculenta are pretty meaningless. The whole thing (wild types and cultivars) should botanically just be called C. esculenta, and (the) diversity of cultivated forms reflected in cultivar and cultivar group nomenclature."
If those in the know are of divided opinion, gardeners cannot be expected to sort out the name issue. To grow these lovely plants, you just need to know whether the one you crave is a wetland or dryland type. The wetland taros can be grown in dryland conditions (i.e. not in a pond or bog, but with moist soil), but dryland types will rot if grown in a pond or bog. This distinction is not easy to sort out from nursery lists, since the type of plant is seldom listed. The best advice is to do some research. If many resources say you can grow the plant in water, then it is sure to be a wetland type. If they don't, then you'd best consider it a dryland type.
The wetland types are native to swampy areas in tropical southeastern Asia and will grow in as much as a foot (30cm) of water. The dryland or upland taro, is widely cultivated in China, Japan and the West Indies, both for ornamental foliage and food.
If you live in Florida or the Gulf Coast, near a body of water, you need to be very careful about planting the wetland types in the garden since they have escaped cultivation and are becoming a pest in waterways.
The leaf stems (petioles) can reach between three and seven feet (.91 - 2.13m) in length and the leaves can grow two or three feet long (.6 - .91m).
This view of my group shows C. esculenta 'Black Magic', newly acquired this year. This is also the first year that I have grown any of these in the ground; previously my no-name plant occupied an enormous pot. In the ground it has reached well over five feet in height (1.52m) this season.
I had read a post from someone noting that her plants were very happy in a mud hole. Since a mud hole was something I could make, I thought I'd try it. It has worked beautifully and it's simple to do in clay soil. I dug a large hole deep enough so that the top of the soil in the hole is about four inches (10 cm) lower than the surrounding grade. I amended it fairly well, but I realize now that these are very heavy feeders and I might have gotten larger plants if I'd made the backfill half manure. Every day during summer, I just ran the hose until the hole filled with water. About half way through the season, I dumped half a bag of composed cow manure in the hole and spread it around.
'Black Magic' particularly benefits from heavy feeding, I have learned. Next year, it will get more manure more often and may get closer to its height of six feet (1.82 m)! This cultivar is nirvana for those of us who covet purple foliage. Not only is the leaf color so deep it appears black, but the leaf texture is almost velvety...you simply have got to stroke this leaf when you pass it. Plus, the stems match the leaves! This is a water lover and can be used as a pond marginal.
'Black Magic' was imported into the US by California's Walter Pagels, a former editor of the Water Garden Journal and member of the IWGS Hall of Fame, who, according to Tony Avent, found it in a botanical garden in the Philippines. Tony says that it has proved to be reliably hardy to 0ºF (-17ºC) in his trials, although it can be slow to return from dormancy. Am I brave enough to try this outside over winter???.
There are many named cultivars of Colocasia being offered today. While in Raleigh, North Carolina this summer, I took photos of some that are now on my wish list. Colocasia esculenta 'Yellow Splash' is one of them.
If you like variegated foliage, this one is for you.
I have not been able to find any specific information about this plant. It was growing in Alan Galloway's border and, while not tiny, was not as tall as mine growing in the mud hole.
Also in Alan's garden was C. esculenta 'Burgundy Stem', which is now on my lust list. I need this plant.
This one can also get six feet (1.82 m) tall, with leaves up to three feet (.91 m) long. The leaves are green with a slightly hazy purple cast. If it flowers (which I have yet to see on either of mine), the are yellow and about a foot tall (30 cm). Tony Avent says they smell like papaya. This one sends out runners, so I am guessing it may be dryland type.
The stems are extraordinary - like a lacquered eggplant.
All of these Colocasia are hungry plants who will perform best in highly organic soil in sun or part shade.
Most of them seem to be hardy in the ground from zone 7b south - at least they are being grown in the ground with little protection in Raleigh, NC.
For those living in colder climes, they can be dug and overwintered in a frost free place.
Those that make tubers/corms can be stored dry or kept in a pot on the dry side in a place that is about 50ºF (10ºC).
Those that do not form tubers/corms need to be potted and can be kept growing in the house if you can give them enough light and increase the humidity from normal heated room humidity.
If you live well north of USDA zone 7b, it would be easier to simply grow these plants in pots, hauling them out for summer and in for winter, than planting them in the ground and having to dig them up. I've also read that the soil in northern climates does not warm enough for optimum growth, but that soil in a pot where summers get hot, will be warm enough.
Current thinking is that the key to overwintering them in the ground in the cooler part of zone 7 (and possibly farther north) is to keep them dry. It's not so much cold that kills some of these tropicals as wet cold. I intend to give this a try this year. To hedge my bets, I will dig up some pieces of my plants and then, once frost kills the foliage, remove it and cover the crowns with manure, mulch, plastic and more mulch. When spring comes and the temperatures start to warm up, I will remove the top mulch and plastic and let them (hopefully) grow up through the bottom layer of manure and mulch, which ought to help feed them, too. We shall see whether or not this succeeds!
Alocasia
I keep finding reference to there being seventy species of Alocasia, but only seventeen species are listed in W3TROPICOS and I have yet to find a listing showing more than that.
Alocasia and Colocasia were once considered the same genus (Colocasia) and there still seems to be massive cross-over in references that mention them by common name, since both are called Taro and many species of both are edible. The differences between them, according to the gurus on Aroid-L, are:
- The most important difference between the two is microscopic, found within the female flowers. In Colocasia the placenta is along the interior sides of the embryonic future berry from top to bottom with the many "stems" of the ovaries attached to the placenta along the interior sides of the ovary. In Alocasia the placenta is basal, and a sparser number of ovaries and "stems" are attached to it within the embryonic future berry but along its interior base.
Glossery-
Peltate: On a stalk attached to the lower surface of the leaf rather than to the base or margin of the leaf.
Sagittate: With a downwardly pointed lobe on each side of the base.
Pinnatifid: Pinnately lobed half the distance or more to the midrib, but not all the way to the midrib.
Spadix: A spike with small flowers crowded on a fleshy axis, characteristic of the Araceae family (the "jack" in the pulpit [spathe]).
Spathe: A large bract beneath and enclosing the inflorescence (flowering part of the plant).
Petiole: Leaf stem.
- Generally (not always) Colocasia has a partially peltate leaf blade, while Alocasia leaf blades can be any shape imaginable from entirely peltate to sagittate, to deeply pinnatifid.
- Generally (not always) Colocasia has a small sterile region at the tip of the spadix, while Alocasia has a longer sterile region at the tip of the spadix.
- Colocasia produce inflorescences in a fan running away from the petiole from which they are being produced (i.e. the back of the spathe faces the petiole from which it is produced), and, generally, produces several inflorescences per leaf. Alocasia produces inflorescences running parallel to the leaf and, generally, only one or two per leaf.
- Alocasia produces rather large, odorless berries carried erect, that ripen orange-red, each containing one to three (rarely more) large, round seeds. Colocasia produces small, yellow-brown, fruits on a nodding stalk that have a fruit scent and contain many, small, ellipsoid seeds.
Alocasia come in all sizes. Alocasia robusta, is a giant, endemic to Borneo from forest clearings to stream sides. It is said to have the largest undivided leaves in the world, which can reach up to thirteen feet (4 m) in length. From New Guinea, Alocasia portei can reach ten to fifteen feet (3.04 - 4.57 m) in height, forming a trunk that is almost palm like. It is said to be similar to A. macrorrhiza, but with deeply lobed leaves held upright.
At the other end of the spectrum, the leaves of Alocasia reginae mature at about ten to twelve inches (25 - 30 cm). The intense silver of these leaves is fantastic. Picture this growing out of a swath of one of the purple leaf sweet potatoes! (Ipomoea batatas)
Alocasia macrorrhiza 'Variegata' is going to be my first Alocasia. Just look at that leaf! The leaves were easily over three feet long (.91 m).
The entire plant was so large it took three separate images to capture it. These photographs were taken at the butterfly house in Durham, NC this summer, where I met this plant and immediately fell head over heals in love with it.
Like many colocasias, some alocasias are also edible. A. macrorrhiza is one. It has been grown for the edible corm/tuber for centuries throughout tropical Asia.
The Hawaiians cultivated it, calling it ape (ah-pay), although, today, I have read that apes are generally grown by the Tongan and Samoan people who live in Hawaii as the true Hawaiians prefer colocasias. I've also seen A. macrorrhiza referred to as wild taro in some references or giant upright elephant ear or giant taro in others. It has many common names throughout the regions where it's grown. This species is native to tropical forests in Sri Lanka, India and Malaysia where it is part of the understory, found in clearings and along streams.
This image shows the stems that held the leaf in the previous image, plus smaller leaves coming on. What amazes me about this plant is the amount of white on the leaves. Lack of pigmentation usually results in plants that are not very robust, which this child definitely is!
A. macrorrhiza can easily grow well over six feet (1.8 m) in height in the ground; under ideal conditions, A. macrorrhiza 'Variegata' can reach eight to ten feet (2.43 - 3.04 m) tall. They prefer deep holes with rich, moist, organic planting material, and while liking a bright situation, do quite well in partial shade, tolerating almost full shade. A. macrorrhiza loves humidity and can tolerate shallow flooding, but is not at all tolerant of salt.
Often rated hardy only in USDA zones 9-11, this is another species that seems to winter over in USDA zone 7b, Raleigh, NC, surviving 0ºF (-17ºC), according to Tony Avent, but preferring warmer temperatures.
In addition to the incredible variegated leaves, the petioles are also variegated. These images do not give you the full impact of this plant. It simply took my breath away.
The leaves emerge from the center of the plant, from within the innermost leaf petiole (stem). In active growth, the petiole becomes larger with each new leaf produced. After the leaves die back, they leave a husk, which, if removed, shows a ring scar for every leaf.
Propagation is by severing the rhizomes between upright stems or separating offsets from the parent plant. Stem cuttings also root readily in spring and summer. If you are lucky enough to have your plants flower (the greenish spath is about eight to ten inches tall (20 - 25 cm) and not terribly showy), you can plant the reddish seeds that develop along the spadix as soon as they ripen. They will germinate in warmth.
If you want to grow these plants in a warm greenhouse, give them a minimum temperature of 60ºF (15ºC), partial shade and high humidity. Pot them in a well drained mix of ground bark, soil, sharp sand and charcoal, planting them so that the top of the rhizome is not below the pot rim. If you pot too low, the bottom leaves may decay at the base. Water freely while in active growth, decreasing water in autumn as the leaves start to fade.
Xanthosoma
Unlike Colocasia and Alocasia, who are of tropical and semi-tropical Asian origin, Xanthosoma is a native American genus. As a rule of thumb, xanthosomas will have a sagittate leaf blade ( there are a few exceptions to this) with a smooth, sometimes waxy upper surface and thick ribs on the lower surface, often quilted at the veins. It also has a collecting vein that runs all around the leaf, just inside the margin. The petiole attaches at the notched edge of the leaf, unlike Colocasia, where the petiole attaches away from the edge of the leaf.
I counted one hundred six distinct species listed on W3TROPICOS plus numerous varieties. There are many edible forms of Xanthosoma sold in the US under the blanket common name of malanga. Other common names include yautia, tannia and tanier for forms that produce tubers/corms (the cocoyams) or belembe and calalous for those grown for leaves. They're also called arrowleaf and elephant ear, plus numerous names in tropical South America, where it is indigenous.
Those forms that make tubers/corms have a large central tuber/corm with a cluster of cormels around it. Thousands of acres of land in Florida are planted with malanga to meet the demands of the Latin Americans living there.
Listed mostly as hardy from USDA zones 9 to 12, Xanthosoma will grow in full sun or partial shade. It needs high humidity and well-drained soil with adequate moisture. It can be grown as a container plant in cooler climates with an optimum growing temperature of around 80ºF (26ºC).
Xanthosoma mafaffa aurea 'Lime Zinger' or 'Green Giant' or 'Lime Green' or simply 'Aurea' or aurea - looks to me like Ipomoea batatas ‘Margarita’ on steroids. Since 'Margarita' is a favorite of mine, this plant (by whatever name) has also landed on my list of 'must haves'. It is said to reach three to four feet (.91 - 1.21m) in height. Dewey Fisk says on his web page that he once saw it reaching twelve feet (3.65 m) "in an area that had a nice tree canopy and lots of ground moisture and humidity". Wow! I have discovered that this particular shade of glowing lime green is a perfect foil for the purple leaf plants I adore, who really do need a bit of bright foliage to set them off or they rather fade into the woodwork.
There are simply too many of these three genera that I crave.
More wild and wonderful Aroids next time. See ya' later!
More Information
- If you find yourself becoming smitten with Aroids, join International Aroid Society. You'll find information about Aroids and links to many images on the IAS web site.
- Lester Kallus' Aroid collection - marvelous photos of several species plus a page of edible aroids sorting out the various common and botanical names for those generally available in supermarkets and ethnic grocery stores. He also has a link to the IAS Aroid Identification page where photos of unknown plants are posted to be identified.
Photos of more Wild and Wonderful Aroids:
- Alocasia macrorrhiza variegata 'Mickey Mouse'
- Alocasia guttata 'Imperialis'
- Alocasia indica 'Metallica'
- Alocasia lowii
- Alocasia sanderiana 'Nobilis'
- Alocasia x 'White Knight'
- Colocasia esculenta 'Illustris'
- Allan Galloway has a fabulous garden in Raleigh, NC, where he grows many aroids. He has put up galleries of photos for:
- Krzysztof Kozminski also has a page of Alocasia images, including some group photos showing the immense variation in leaf shape and size. one with two Colocasia species and one of Xanthosoma.
- Alocasia brisbanensis, endemic to Australia.
Image Credits
All images are by Marge. Do not use these images without written permission!
| Gardening in Shade is just one of the of over thirty different gardening topics you can visit here on Suite 101, covering everything from annuals to zucchini. If you're not a member of Suite101 Be sure to check out the gardening courses at the Suite University! |