Cool Colocasias
Elephant Ears for the Garden

Hawaiian Eye Elephant Ear photo by Plant Delights Nursery

By Dennis Carey and Tony Avent
Plant Delights Nursery Inc.
9241 Sauls Road
Raleigh, NC 27603
919.772.4794

The Colocasia Family

Colocasias are known in the western world by three common names; taro, kalo and the descriptive anatomical name, elephant ear. There are dozens of common names used in other parts of the world including culcas (from which the genus name colocasia is derived), eddo, imo, dasheen, cocoyam and malombo. Colocasias have a worldwide distribution and are grown in tropical and sub-tropical countries as a vital staple food crop and fodder crop. Colocasia esculenta is the 14th most widely consumed vegetable on earth. Ornamental colocasias (the focus of this article) are important plants in gardens because they add a bold, tropical look.

The common name, elephant ear, is also occasionally used to describe plants in related genera such as alocasia, remusatia, and xanthosoma. The leaves of the elephant ear plant and its relatives are typically large, flat and sagittate to broadly ovate in shape and really do look like they belong on a pachyderm's head. The term, elephant ear, is also used to describe both the unrelated plant Burdock in the genus arctium and a delicious fried dough treat at most State Fairs. Oddly enough, the genus name colocasia is also used for a European moth.

Colocasias belong to the araceae family (whose members we call aroids) and share the unique spathe and spadix inflorescence of other aroid genera such as spathiphyllum (Peace Lily). The genus colocasia contains slightly more than a dozen species with several new ones being described recently. The vast majority of the cultivars used in ornamental gardens belong to Colocasia esculenta. There are also a small number of attractive varieties of lesser known species such as Colocasia affinis, Colocasia fallax, Colocasia gigantea, and Colocasia heterochroma available for discriminating gardeners. Other species may also have garden potential but are not yet in cultivation. These include Colocasia bicolor, Colocasia formosana, Colocasia gaoligongensis, Colocasia gongii, Colocasia konishii, Colocasia lihengiae, Colocasia menglaensis, Colocasia oresbia, Colocasia tibetensis, and Colocasia yunnanensis.

Esculenta varieties are normally diploid (2n=28) as are many of the other species in the genus. However, triploid (3n = 42) varieties are not uncommon in cultivation and are usually more cold tolerant. Colocasia species will rarely cross with other colocasia species and supposedly with alocasia. A few intergeneric and interspecific hybrids have reportedly been discovered or hybridized, including Colocasia esculenta x Alocasia brisbanensis, Colocasia esculenta x Colocasia gigantea, and Colocasia gigantea x Alocasia macrorhizos. In 2005, we found a plant in Northern Vietnam that we assume to be the latter cross, but we'll be sure when the DNA analysis is complete.

History of Colocasia

Elephant ear plants have been in cultivation for over 28,000 years as a food crop in equatorial regions including India, China, Southeast Asia, Indonesia, Polynesia, the Mediterranean, Africa, and South America. Because colocasia has been in cultivation for so long, no one knows for sure where it truly is native, but all evidence points to somewhere in Southeast Asia. All parts of the plant are edible if they are thoroughly steamed or boiled to first remove calcium oxalate crystals. The cooked leaves are used in Hawaiian luaus and the corms are mashed into poi. Prior to the mid-1800s, colocasias were a staple food crop and the native Hawaiians cultivated hundreds of varieties. Modern agricultural crops have supplanted colocasia in Hawaii and the number of commercially grown varieties has plummeted. However, beginning in the 20th century, agricultural scientists started to preserve the Hawaiian colocasia varieties and breed new ones. These breeding efforts have also led to the development of many new ornamental varieties.

Growing Colocasia

Colocasia culture is fairly simple. Just remember the mantra: "more water + more nutrients = more plant". Gardeners can grow potted Colocasia esculenta cultivars in shallow bodies of water, but other species, such as Colocasia gigantea, need better drainage. Colocasias grow very well as a pond marginal, and when grown in containers, the pots can be submerged slightly during the summer months. Containers of colocasia must be brought indoors in cold winter climates.

Colocasias are heavy feeders and for best performance require organic fertilizers and rich organic soil with plenty of composted material. A pH from 5.5 to 7.0 is satisfactory. Most colocasias prefer bright sunlight, unless grown in extremely hot, low humidity climates, where some light shade will be necessary. Elephant ears should be planted slightly deeper than they grow in the pot, or when planting dormant corms, put them at a depth of 2" to 4".

During the growing season, colocasias will continually produce new leaves as the older leaves continually die off. Growers will want to periodically remove the dead leaves in order to prevent the leaves from covering ground-cover plants and to keep the garden looking tidy. Some gardeners may be sensitive to the juices of cut colocasia stems (which contain calcium oxalate) and may notice some skin or eye irritation unless they wear gloves or wash their hands soon after contact.

Propagation

Colocasias can be propagated by seed collected about 30 days after fertilization, and surface sown as soon as possible after drying. Germination should take place within 21 days. In addition you can divide the larger corms, collect offsets (cormels) or separate the new plantlets that form at the rhizome tips on the running types. The long runners form nodes along their length, and new growth buds exist at each of these nodes.

Overwintering Colocasia

As the day length shortens, colocasias switch their energy resources from producing leaves to flower and corm production. The production of leaves will become smaller and the corm will swell noticeably. At this time, most of the current season's roots will die off. It is important to understand this physiological change in order to successfully overwinter your elephant ear.

There is also quite a difference in winter hardiness of colocasias. Colocasia gigantea 'Thailand Giant' is a solid USDA Hardiness Zone 8b, while Colocasia 'Pink China' is reportedly winter hardy to Zone 6. The rest fall somewhere in between. Typically, triploid cultivars are about a half zone hardier than their diploid counterparts. From Zone 8b south, most colocasias should be reliably winter hardy in the ground without protection. This successful zone of cultivation also extends into Zone 8a, but some marginally hardy cultivars may be slow to return after a hard winter.

In Zone 7b, most colocasias will return without benefit of mulch with a few exceptions. Colocasia affinis 'Jenningsii', Colocasia esculenta 'Nancy's Revenge', Colocasia gigantea 'Thailand Giant', and Colocasia esculenta 'Elepaio', need slightly warmer winters (zones 8a-8b) to return without benefit of winter protection. In this hardiness zone, hardy colocasia may survive, but the large central corm can freeze and rot during the winter, leaving only the smaller offsets to survive. In this case, returning plants may not reach full size during the ensuing season. To overcome this, cover the clump after the first frost with a 1' tall pile of shredded leaves, which works well to protect the main corm. The plants will grow through the leaves when they re-emerge in spring.

In colder zones, the same principle can be used but with a slightly altered technique. Assuming the plant has made good growth during the summer, after the first frost, encircle the base of the plant with a 3' diameter cage of hog wire and fill it with shredded leaves. If left unshredded, the leaves will pack together and hold unwanted moisture against the plant, causing it to rot. When new leaves emerge in spring, remove the cage and filler.

Northern gardeners (Zone 7a and north) will need to bring their elephant ears indoors before the temperatures drop below freezing. Over winter, elephant ears can be grown indoors as potted house plants. If you grow your elephant ears outdoors in containers during the summer, cut back all but the top two leaves, then bring the pot indoors the before first frost. If growing elephant ears in the ground during the summer, pot them before frost in an appropriately-sized container and place the pot in a cool area (45-60F is ideal) where the plant receives bright light. Do not over water in winter as the plants are still semi-dormant.

Most of the dwarf non-corm forming species should be kept growing during the winter, along with non-tuber forming selections of Colocasia esculenta including Colocasia esculenta 'Black Magic' and Colocasia esculenta 'Nancy's Revenge'. Colocasia gigantea 'Thailand Giant' is also slow to develop a large corm, so is best kept in active growth.

Varieties of colocasia that form large corms, such as most Colocasia esculenta cultivars, can be dug up and the corms stored in peat moss for the winter. They need to be kept in a dry, cool, but above-freezing location. Do not store in an airtight container which may allow moisture to build, causing the tuber to rot. Don't forget to label your tubers!

Clumpers versus Runners

Colocasias can be divided into two groups: the clumpers and the runners, although some cultivars blur the lines. Early edible colocasias grown for taro was originally the form Colocasia esculenta variety aquatilis. This form produces very long stolons (above ground runners), forming a large mass of plants in a short time. While this trait may be good for large plantings, it is less desirable in a garden of limited space. In tropical climates such as the Gulf Coast, they can truly take over, which gives all elephant ears an undeserved bad reputation in these climates.

Many modern elephant ears bred with these early plants still have above ground runners, although the degree of running is somewhat less. The only colocasias that spread by below ground runners are Colocasia esculenta 'Illustris' and its close cousins, Colocasia esculenta 'Black Beauty' and Colocasia esculenta 'Coal Miner'. The clumping varieties have an attractive vase shape in the garden, and many of the cultivars available today are very slow or are nonexistent runners, just like me.

Elephant Ear Breeding

We first became interested in elephant ears in the late 1980's, but it was on a 2003 trip to Hawaii looking for elephant ears that the scope of our interest and knowledge of the genus changed dramatically. Here, I met Dr. John Cho, of the University of Hawaii Experiment Station on Maui. A plant pathology professor, Dr. Cho was breeding edible Colocasia for leaf spot resistance, unaware that anyone would be interested in their ornamental value. I was speechless at his complete collection of all the known cultivars of Hawaiian edible taro, along with his amazing hybrids. In the ensuing months, we established a formal trialing relationship with Dr. Cho and the university, which continues to this day. Every year thereafter, Dr. Cho has visited Plant Delights, where we spend several days evaluating his hybrid elephant ears and discussing possible future crosses. In Fall 2005, the management of the program was handed off to Planthaven, a California-based plant marketing firm and the first six plants were commercially released in 2008. Dr. Cho retired in 2009, but is continuing his breeding work to develop unique and gardenworthy ornamental taro selections.

Ear Color Choices

The leaves of elephant ears are their most important ornamental trait. The most common color is a rich emerald green, but now leaf colors can range from black or brown, to chartreuse gold. In addition, the leaves will vary in glossiness from a matte finish (common) to a high gloss shine (rare in colocasia). It is also quite common to find leaves containing thick mid veins and major side veins of a contrasting color. The major veins may be green, purple, creamy ivory, yellow or pink (who doesn't like a pink elephant?). The extent of the vein color varies. The coloration may only occur at the "piko" (the "belly button" on the top of the leaf opposite the point of attachment to the petiole) or may run through all of the major veins of the leaf. In addition, the mid-vein coloration often leaks into the surrounding lamina tissue and may form an oval shape as with Colocasia esculenta 'Nancy's Revenge' as the season progresses. This trait appears to be triggered at the same time as flowering and may be under the same genetic control. It is not uncommon for the bottom of the leaf to have a different lamina or vein coloration than the top of the leaf, which provides a nice flash of color on windy days. The newly appearing leaves may have a different color than when the leaves are mature.

Breeders are also selecting variegated cultivars. Variegation in colocasias often takes the form of variable sized splotches or flecks of color on the leaf surface. Variegations in colocasias are somewhat unstable and reversions are common. Also, the variegation may appear in sectors or only on one side of the leaf. Common color combinations in variegated elephant ears are light green to yellow splotches on dark green leaves, green splotches on purple leaves, or purple splotches on light green or dark green leaves. The leaf variegation also runs down the petioles, where it is often more visible than in the leaves.

The elephant ears that gardeners seem to get most excited about are the solid purple-leaved or solid black-leaved esculenta cultivars. The color purple makes a great contrasting color in the garden and on plants as large as elephant ears, purple makes a bold statement. The purple coloration can vary from a dusty gray-purple to extremely dark purples which appear black. Black elephant ear plants are wonderful to have unless you like to spend time in your garden at night! The purple-leaved cultivars usually have a matte finish, although there is one moderately glossy purple-leaved cultivar in the trade, Colocasia esculenta 'Diamond Head'. In the future, look for purple- or black-leaved cultivars with extremely glossy foliage (I can't wait!).

In addition to color, breeders are selecting for various leaf shapes and textures. Leaves may be somewhat arrow-head shaped (sagittate), or may be roundish on the sides, like a fat arrow-head. Generally, the leaf tip (apex) is pointed (acuminate) and the leaf base has two pointed or rounded lobes of varying size with a "Y" shaped sinus between them. The leaf margin may be smooth or ruffled. The leaf surface may be smooth, somewhat puckered, or even cupped in such a way that it can hold quite a bit of water. Some cultivars that are in the pipeline right now will feature the brand new trait of reflexed leaf edges. All colocasia leaves are hairless (glabrous) and have a smooth waxy feel.

The leaves are held up by very long thick petioles that emerge directly from the underground corm. The petiole to leaf attachment is "peltate". In other words, the petiole does not attach to the edge of the leaf, but rather to the middle of the lower surface of the leaf. As a result, the leaves are held perpendicular to the petiole. The petioles grow nearly straight up, but the leaves are generally upward or outward facing. The petioles may have attractive colors that contrast with the leaf. The petiole color may be black, purple, burgundy, maroon, red, pink, cream, or they may be streaked with several colors at once. The petioles are thick enough so that their color is easily noticed and is a nice ornamental feature.

Flowers

Colocasias are not known for their flowers (inflorescences, actually) because they are hidden underneath the leaf canopy. However, the inflorescences are large, quite attractive and frequently fragrant ... although only just as the spathe opens. The spathe and spadix inflorescence (think calla lily, a fellow aroid) is held on a short peduncle and may be up to 8" long by 3" wide (but usually smaller). Spathe color is usually white or yellow and spadix color can vary from creamy white to yellow or orange. The fruits (which are rare unless you hand-pollinate) are a cluster of small berries, 3 to 5mm wide, that are greenish or yellowish in color with several seeds inside.

Size Matters

Colocasias vary in size from the diminutive Colocasia heterochroma 'Dark Shadows' at only 8" tall to the mammoth Colocasia gigantea 'Thailand Giant' which can top out at over 9' tall in ideal conditions. Most varieties fall within the 3' to 5' tall range. The leaves also vary in size from only 4" wide by 6" long on Colocasia heterochroma 'Dark Shadows' to 4' wide by 5' long in Colocasia gigantea 'Thailand Giant'. The large-leaved varieties are truly an amazing sight to behold.

For the purposes of this article, we'll divide colocasias into 3 categories: the "dwarf" types, the "giant" types, and the "esculenta" types, as these are the categories that have different uses in the garden. In the following paragraphs, we've separated the cultivars into these categories in order to help you select the best plants for your site.

Dwarf Elephant Ears

The dwarf Colocasias include any taxa that are less than 2' in height. These are small plants that look good planted en masse or as accessories for other small tropical plants. There are some small C. esculenta cultivars, but they will be discussed under the "esculenta" type Colocasias.

Colocasia affinis is a charming but little-known dwarf elephant ear that is loved for its picture-perfect, velvety charcoal leaf face with central charcoal veining and a giant silver blotch in the center of each leaf. Much of the material sold as this is actually Colocasia esculenta 'Illustris' (no central silver pattern and green veins). This 1' tall, light shade and moisture-loving species has proven to be a superb garden plant. Throughout the summer, the dense clumps are adorned with small flowers of the yellow spathes and spadix persuasion. For us, Colocasia affinis resprouts in late June, so don't panic! Colocasia affinis is represented in the trade by the cultivar Colocasia affinis 'Jenningsii'. Since we have not grown other cultivars of this species, we don't know how different this is from the typical species. Like Colocasia heterochroma, Colocasia affinis goes winter dormant regardless of the temperature. (Hardiness Zone 8-10)

Colocasia fallax is a delightful dwarf elephant ear from China. Unlike most other elephant ears, this light shade and moisture lover forms rounded leaves of velvety medium green, each highlighted by a wide silver streak down the center vein, with smaller silver veins radiating from the center to the leaf edge. The plants are adorned all summer with small yellow spathe and spadix flowers. The 15" tall plants make a 4' wide patch in 2 years (in very wet soils) by means of short, above-ground stolons ... quite unique and quite beautiful (Hardiness Zone 7b-10).

Colocasia fallax is represented in the trade by the cultivar Colocasia fallax 'Silver Dollar', a PDN introduction composed of small, rich green leaves much more rounded than normal and also highlighted by narrow silver veins and a wide central silver blotch ... not to mention held atop cinnamon-colored petioles. We are also growing another selection, Colocasia fallax 'Silver Splash', which seems a bit taller, reaching 18-20", but spreads less vigorously than other forms we grow.

The smallest of the dwarf colocasias is Colocasia heterochroma which measures a Lilliputian 8" tall. This fascinating new colocasia species was discovered at 4,000' elevation in Yingjiang, Yunnan Province, China. The plant was subsequently named in 1993 by China's aroid expert, Dr. Li Heng. Colocasia heterochroma, a June emerger which prefers light shade, forms a small patch via short underground rhizomes to only 8" tall x 18" wide ... a far cry from its taller cousins. The 6" long x 4" wide leaves are silvery green with a dramatic black interveinal leaf pattern. Unlike most other colocasia species, it goes dormant in winter even if kept warm. Colocasia heterochroma 'Dark Shadows' is a cultivar that we named with particularly dark leaf patterns. (Hardiness Zone 7b-9)

Mid-Sized Elephant Ears

The second type of colocasias in this article are the Colocasia esculenta cultivars which represent the majority of the taxa in the trade today. They vary in height from 2.5' to 5' tall, and where the climate allows, prefer full sun unless indicated differently. Colocasia esculenta has the widest color and leaf shape variation, and range of variegation of elephant ears. Some have a clumping habit, and some are runners. The solid green-leaved, clumping Colocasia esculenta is the most common in the trade and can often be found as a dormant corm even in the large box stores. The common Colocasia esculenta produces a 5' tall, green-leaved plant with 2.5' wide by 3.5' long leaves with green petioles and a smooth margin (leaf edge). Colocasia esculenta is represented in the trade by the following cultivars.

Colocasia esculenta var. antiquorum 'Black Beauty' is a superb 2006 Agri-Starts introduction, a stunning mutation of the popular Colocasia 'Illustris'. If you can imagine intensifying the black leaf color and removing some of the green veins of Colocasia esculenta var. antiquorum 'Illustris', you can visualize Colocasia esculenta var. antiquorum 'Black Beauty'. In the ground, Colocasia esculenta var. antiquorum 'Black Beauty' forms a 30" tall patch, spreading underground like Colocasia esculenta var. antiquorum 'Illustris', making a 4' wide patch in 3-4 years ... simply stunning. (Hardiness Zone 7-10)

Colocasia esculenta 'Black Magic' was introduced by California's Walter Pagels. This revolutionary plant was the first of the solid black-leaf elephant ears to be introduced. The dusty, solid purple-black leaves to 2' long, make this elephant ear one of the most spectacular forms ever introduced ... especially great for designers who love purples and blacks! It makes a giant clump to 5' tall with a similar spread. Our original plant came from Bob Whitman at Southern Exposure Nursery Texas in the early 1990s. For a while, Bob lost the label on his plant and mistakenly re-labeled some he sold as Colocasia 'Jet Black Wonder', an error which unfortunately still persists in the trade. (Hardiness Zone 8a-10)

Colocasia esculenta 'Black Marble' (aka Colocasia 'Multiflora') is an Agri-Starts introduction that sported from the old favorite Colocasia esculenta 'Burgundy Stem'. Each 3' tall clump is composed of dark gray-green leaves, highlighted by random purple-black sectors and flecks. Despite the instability of the pattern, the patterning does persist throughout the entire plant. Due to this instability, Colocasia 'Black Marble' has a high cull rate in production and will never be produced commercially in huge numbers. This and the fact that Colocasia 'Black Marble' is a weak grower will always keep it quite rare. (Hardiness Zone 7b-10)

Colocasia esculenta 'Black Runner' is a newer black-leaved cultivar that represents a change from Colocasia esculenta 'Black Magic'. Colocasia esculenta 'Black Runner' is probably a mutation of the popular Colocasia 'Black Magic'. Colocasia esculenta 'Black Runner' makes a stunning 5' tall clump with 2' long leaves that emerge more of a black-purple than Colocasia esculenta 'Black Magic'. Its leaf edges are also much more ruffled than its cousin. However, the biggest difference is the black, snake-like runners creeping along the ground, pegging into moist soil every few inches and sending up new plants. (Hardiness Zone 8a-10)

Colocasia esculenta 'Blue Hawaii' PP 20,003 is a 2008 John Cho hybrid, composed of medium green 12" long leaves highlighted by the most dramatic purple veins we've ever seen on an elephant ear. On the leaf back, the veins are equally dramatic, only cranberry instead of purple. This small elephant ear tops out for us at only 30" tall ... perfect for a smaller location. Remember, rich moist soil grows the best elephant ears. (Hardiness Zone 7b-10)

Colocasia esculenta 'Chicago Harlequin' was discovered by John Joicus of the Brookfield Zoo circa 1993, in a batch of normal Colocasia esculenta. The giant green leaves of Colocasia esculenta 'Chicago Harlequin' are each blotched with large, lighter green, random sectors. The highlight, however, is the tall 5' stems, which are vividly striped with cream-and-green vertical bands. Colocasia esculenta 'Chicago Harlequin' spreads rapidly in very wet areas by means of above-ground stolons. (Hardiness Zone 7b-10)

Colocasia esculenta 'Coal Miner' is a 2007 Plant Delights Nursery introduction. Several years ago, we received plants from India as Colocasia antiquorum. One exceptional clone was later christened Colocasia esculenta 'Coal Miner'. In appearance, Colocasia esculenta 'Coal Miner' looks like a larger version of Colocasia 'Illustris' except for emerging 2 months earlier (late March in NC), not spreading underground as vigorously as Colocasia 'Illustris', and being a diploid as compared to the triploid status of Colocasia 'Illustris'. The black leaf pattern is also similar to Colocasia 'Illustris', but the background leaf color is quite different (dark olive vs. medium green), and the emerging new leaves have a stunning velvet patina. For us, Colocasia esculenta 'Coal Miner' tops out at 54" tall, while Colocasia 'Illustris' only reaches 40" for us. (Hardiness Zone 7-10)

Colocasia esculenta 'Diamond Head' PP 19,939 is a 2008 release from John Cho's breeding program that takes elephant ears to a whole new level. With this introduction, John has been able to combine the color of Colocasia esculenta 'Black Magic' with the glossy leaf surface usually seen only in alocasias. The 15" long, glossy, chocolate-black, lightly ruffled-edged leaves compose a well-behaved 4' tall clump. (Hardiness Zone 7b-10)

Colocasia esculenta 'Elena' is a more winter hardy replacement for the tropical Xanthosoma 'Lime Zinger'. This chartreuse-leaf elephant ear was found as a sport of Colocasia 'Chicago Harlequin' at Alan Shapiro's Grandiflora Nursery by Randy Strode of Agri-Starts, and subsequently named after Alan's wife, Ellen. Our clumps, which top out at 3' tall, are composed of creamy ivory stalks that turn purple where they join the leaf. The stalks are topped with 20" chartreuse leaves with purple veins where the stalk attaches ... perfect for some cool color combinations. Colocasia esculenta 'Elena' will spread by aboveground rhizomes when planted in moist sites. After cold winters, this is very late to re-emerge. (Hardiness Zone 7b-10)

Colocasia esculenta 'Elepaio' is named after the rare Hawaiian flycatcher bird. This very rare, 30" tall elephant ear is one of the classic old Hawaiian cultivars. Colocasia 'Elepaio' makes a small, 3' tall clump of green foliage that is heavily spotted with white paint-like flecks. This unstable chimeral variegation pattern often results in some leaves that are half green and half white. This is a true curiosity and what we call a "fun" plant for the garden. (Hardiness Zone 8a-10)

Colocasia esculenta 'Hawaiian Eye' PP 19,884 is a 2008 John Cho introduction that makes a 4' tall non-running clump, composed of large 18" long leaves that emerge black with silver-gray veins. As the leaves age, they morph to gray green, each highlighted by a dark central eye of purple radiating out into the leaf. Each leaf is further highlighted by a narrow purple border and a great backside as the veins on the reverse appear to be bright cranberry. The glossy jet black stem is a stunning contrast to both the leaves and the bright yellow flowers in late summer. (Hardiness Zone 7b-10)

Colocasia esculenta 'Hilo Bay' PP 20,108 is a 2008 introduction from the breeding program of Hawaii's John Cho, that makes a unique 4' tall specimen with thick, dark chocolate stems, each ending with a 20" olive green leaf. Each thick textured and heavily corrugated leaf with upturned edges is reminiscent of the volcanic rock at Hilo Bay ... very unique. This selection produces short runners as the clump ages, but nothing like the old more aggressive cultivars. (Hardiness Zone 7b-10)

Colocasia esculenta var. antiquorum 'Illustris' is commonly known as Imperial Taro. The 30" tall Colocasia 'Illustris' is one of the most striking plants in our garden after it emerges in early June! This black-leaved elephant ear has dramatic green veins, highlighting the black background ... always a conversation piece. Imperial Taro has proven hardy below 0 degrees F in our garden. The plant is slightly rhizomatous, spreading by short underground runners. It moves slowly in heavy dry clay but abounds freely in wet organic soils. (Hardiness Zone 7-10)

Colocasia esculenta 'Lime Aide' is an Alan Galloway introduction, diagnosed to be borderline schizophrenic ... some leaves are dark green with chartreuse yellow flecks, while others have large sectors of yellow between the green. The leaves are in addition to the cool leaf petioles which are heavily striped green and yellow. This 4' tall plant spreads by above ground stolons. Alan discovered this gem while ditch-hopping in the Philippines ... another reason for expanding this botanical pastime. (Hardiness Zone 7b-10)

Colocasia esculenta 'Maui Magic' PP 19,625 is a 2008 John Cho release forming an impressive 5' tall clump of dark black-purple stems, topped with 2' long leaves that emerge glossy purplish-black and then change to a semi-glossy dark olive-green, highlighted by purple veins, which are even more prevalent on the leaf backs. This is a very robust grower without any sign of runners. (Hardiness Zone 7b-10)

Colocasia esculenta 'Mojito' PPAF (pronounced Mo-he-toe) is a sport of Colocasia 'Burgundy Stem' via Colocasia 'Black Marble', discovered at Florida's Agristarts. Named after the popular Cuban mixed drink, the amazing leaves are medium green with dark purple flecks throughout ... just too cool! Since this clone has less vigor than many others, you can expect the clump to only reach 3', less in drier sites. Although winter-hardy in Zone 7b, the central tuber will often die in the low teens F, so to get larger-sized plants, mulch well in winter to save the central tuber. (Hardiness Zone 7b-10)

Colocasia esculenta 'Nancy's Revenge' was introduced at the 2000 International Aroid Society meeting in Florida, where it was the most drooled-upon plant. Emerging solid green, the 25" long, light green leaves begin turning buttercream-yellow along the center at the onset of flowering, to which the coloring is genetically tied. The color then pours down into the main vein creating a huge, bold Y-pattern in the center of the leaf. Color then bursts into the lateral (side) veins and begins its march to the margins. Colocasia esculenta 'Nancy's Revenge' sends out lots of side stolons that will root into the soil where moisture is adequate. Colocasia esculenta 'Nancy's Revenge' was discovered in the Caribbean and imported by Jerry Kranz, who later named the plant for his business partner, Nancy McDaniels of Florida. The oft seen made up name of Colocasia nancyana is invalid. (Hardiness Zone 8-10)

Colocasia esculenta 'Pineapple Princess' PPAF is a 2008 John Cho hybrid that forms a low 3' tall x 5' wide non-stoloniferous clump, composed of 18" long dusty gray-lavender leaves, each highlighted by dramatic purple veins. The backs of the leaves are equally as dramatic with the dark purple veins showing off against the gray-purple back. This has proven to be a vigorous grower in our trials, flowering well in late summer and fall with spiky yellow flowers, which are fruity smelling as they begin to open ... magnificent! (Hardiness Zone 7b-10)

Colocasia esculenta 'Pink China' is an introduction from Kentucky's Brian Williams, and has been the hardiest elephant ear in his trials, with tubers left on top of the ground surviving outdoors in Kentucky. We have heard unverified reports of hardiness in warmer Zone 5, but we'll believe it when we see temperature documentation. Regardless of the hardiness, Colocasia 'Pink China' makes an attractive 4' tall clump that spreads rapidly by rhizomes to create a large patch. The green leaves are held atop mauvy-pink stems. (Hardiness Zone 6-10)

Colocasia esculenta 'Rhubarb' was "discovered" by Oregon plantsman Burl Mostul on a trip to Hawaii, where he found a clump growing in a suburban garden and realized its potential. The 4' tall stems that hold the large green leaves are brilliant red. We're not talking about a little anthocyanin pigment you have to strain to see, but we are talking real WOW red from 100' away. Be the first in your neighborhood to dazzle your friends. (Hardiness Zone 7b-10)

Colocasia esculenta 'Royal Cho' is the first release from the incredible breeding program of Hawaii's Dr. John Cho. This first release forms a stout 4' tall clump of glaucous-green leaves held atop thick, jet-black stems. The leaves are highlighted by a central purple vein that radiates out into the leaf. The same veins are also prominently visible on the leaf backs as the wind blows. (Hardiness Zone 7b-10)

Colocasia esculenta 'Surf City' is a 2009 introduction from Hawaiian elephant ear breeder John Cho. I've been drawn to this variety since we first put it in our trials. The vigorous growing tight clump is composed of 5' tall stalks that are purple toward the top, each holding a narrowly pointed, amazingly ruffled leaf. Each leaf is adorned with a small purple dot where the stem attaches to the leaf back. The narrow ruffled leaves add an entirely different texture in the garden. This plant was originally introduced as Colocasia 'Waikiki', but this was in error and that name has been reserved for a future introduction. (Hardiness Zone 7b-10)

Colocasia esculenta 'Tiger Stripe' is an Alan Galloway selection that makes a large 5' tall clump of medium green leaves with some chartreuse yellow flecking. The best trait is the stunning stalks, which are heavily streaked with purple and yellow. When the soil is moist, it spreads well via aboveground stolons, forming a large patch. (Hardiness Zone 7b-10)

Colocasia esculenta 'Yellow Splash' is one of several splashed forms entering the US, but this name should only be applied to this cultivar. Each 4' tall clump of large, gray-green leaves is heavily splashed with creamy yellow patterns, differing in each leaf. Colocasia esculenta 'Yellow Splash' spreads via above-ground stolons, so propagation will be easy. Rich organic soils that stay moist in the summer will result in the largest plants. Thanks to plantsman Frank Galloway for sharing this exciting introduction. (Hardiness Zone 7b-10)

Giant Elephant Ears

In stark contrast to the dwarf elephant ears are the towering "giant" type colocasias which max out at over 5' tall or have extremely large leaves. These plants make bold statements in the garden and look great as specimen plants. They can be grown in large containers or they can be under-planted with a variety of small plants to compliment the texture or color.

There are four Colocasia esculenta forms that reach these giant proportions: Colocasia esculenta 'Big Dipper', Colocasia 'Burgundy Stem', Colocasia esculenta 'Jack's Giant', and Colocasia esculenta 'Ruffles'.

Colocasia esculenta 'Big Dipper' is an unusual elephant ear that appears to be a mutation from Colocasia esculenta 'Burgundy Stem'. The 6' tall purple-black stems are topped with gray-green matte finish leaves that are initially held horizontally before they mature to a more vertical angle. The unique effect is that the leaves can actually hold quite a bit of water. When the leaves have too much water, they dump the excess and then return to horizontal to catch more ... fascinating! This is a very vigorous cultivar producing lots of black snake-like runners atop the ground. (Hardiness Zone 7b-10)

Colocasia esculenta 'Burgundy Stem' makes a bold statement in the garden, with 80" tall, deep purple petioles leading to the 3' long, giant green leaves with a slight hazy purple cast, like the air over Los Angeles. The 1' tall yellow flowers have a wonderful papaya-like fragrance. Although it sends out 4' long wild-looking runners, the runners are not overly numerous and the plants don't take over. (Hardiness Zone 7b-10)

Colocasia esculenta 'Jack's Giant' is a plant that we received from Jack de Vroomen of Marlboro Bulb Company, who brought this to us from Costa Rica. The tuber was much larger and shaped differently from other Colocasia esculenta forms we had grown. In our garden, the plants easily reached 7' tall, even in a very dry section, with medium green leaves similar to typical Colocasia esculenta. We are pretty sure it is a triploid form, which should increase winter hardiness. (Hardiness Zone 7b-10)

Colocasia esculenta 'Ruffles' is a spectacular form of the hardy elephant ear that comes to us from a garden in Anniston, Alabama, where it was "discovered" by Southeast Palm Society member Hayes Jackson. We can attest that this 6' tall clumper has both phenomenal vigor as well as hardiness (probably a triploid). Each 3' long leaf has incredibly scalloped edges that sets it apart from typical Colocasia esculenta. In growth habit, it performs here as a clumper, unlike the more stoloniferous forms. Colocasia esculenta 'Ruffles' has also multiplied faster than any elephant ear we have grown, with clumps multiplying from 1 to 100 divisions in 12-24 months. (Hardiness Zone 7-10)

There are a few interspecific elephant ears in the market that aren't Colocasia esculenta, but appear to be a hybrid of that species. I have included them separately, although in growth habit, they behave identically to the Colocasia esculenta selections.

Colocasia 'Fontanesii' is undoubtedly one of the most spectacular plants in our garden. The giant purple-black petioles rise to nearly 7'. At the end of each petiole sits a giant, green, heart-shaped leaf (to 3' long) with a shiny black cast. In late summer, the plant is home to wonderful yellow aroid flowers, to 12" long, with a fragrance of papayas. (Hardiness Zone 7b-10)

Colocasia 'Blackwater' is from a 2003 shipment of colocasia from India of which most were inferior to plants we already grew. However, after several years of trials, one plant stood out that we named and introduced in 2007. Colocasia 'Blackwater' is similar to Colocasia 'Fontanesii' with glossy, jet black stems rising to 6' tall. The stems are topped with glossy, dark olive-green leaves that are much darker and narrower, with a longer leaf tip than Colocasia 'Fontanesii'. It spreads rapidly via black snake-like rhizomes that lay on top of the ground. (Hardiness Zone 7b-10)

Colocasia 'Coffee Cups' is a unique elephant ear, discovered in the wild by Indonesian botanist Gregory Hambali and brought to the US by aroid expert Alan Galloway. Colocasia 'Coffee Cups' makes a stunning 6' tall clump of Colocasia 'Fontanesii' leaves (glossy olive green) with a dark purple-black stem. The unique feature is the dramatic leaf cupping, even more dramatic than Colocasia esculenta 'Big Dipper'. As the leaf fills with water, the stem gives enough for the leaf to dump out its catch before refilling ... fascinating. Obviously, it performs best in freshly ground soil. Colocasia 'Coffee Cups' sends out above-ground runners ... but only in the fall. People seem to have had trouble keeping the name correct. It is often incorrectly labeled Colocasia 'Tea Cups', and worst, most of the plants previously sold in the US under this name are actually Colocasia esculenta 'Big Dipper'. Our trials have shown it to be dramatically less-vigorous than Colocasia esculenta 'Big Dipper' (Hardiness Zone 8a-10)

Colocasia gigantea is a plant that baffled me for years, since the only clone in the trade (until after 2002) was one that we obtained from plant collector extraordinaire Hayes Jackson, that was shared with him by an Asian friend. Despite our best efforts, this plant never exceeded 4' in height, although it was reliably winter hardy in Zone 7b. In addition, it offset quickly despite not making runners, making a large colony in just a few short years, and we have never heard of this plant flowering. I now believe it is either simply a fast-offsetting selection or a Colocasia gigantea hybrid. The upright (unusual for a colocasia) glaucous-green leaves make a clump that more closely resembles an alocasia.

Colocasia gigantea 'Thailand Giant' is the super-sized king of our colocasia collection. This huge strain of the giant elephant ear was grown from wild collected seed (PES 1003B) from Kanchanaburi Province, Thailand, in 2003 by former PDN Research Manager, Petra Schmidt. In the wild, the plants reached a massive 9' tall, which was much larger than others seen throughout Thailand where this species is native. I confirmed this in a 2005 trip and subsequently, none of our other accessions from Thailand have approached this plant in size. For us, each individual leaf grows in excess of 5' long x 4' wide. We have grown this both from seed and now as a clone, and all plants retain the giant size. The leaves are an attractive glaucous-gray which is typical of this species, and from middle age, the plants are adorned with clusters of dramatically large, pleasantly scented, clusters of white flowers.

These are just a sample of the wonderful selections and hybrids that have been evaluated here at Plant Delights Nursery. We have many more exciting and novel cultivars in the pipeline and cannot wait to release them to you. In the future, look for improvements to existing cultivars, better leaf colors, better petiole colors, novel vein colors, more leaf glossiness, better leaf ruffling, novel leaf shapes, better clumping habits, novel variegations, and inter-specific/inter-generic hybrids. We would like again to give a special thanks to Dr. John Cho who has done fantastic work in developing new ornamental varieties of elephant ears for the world to enjoy.

References

Cao, L., and C. Long, (2003). "Colocasia bicolor (Araceae), a new species from Yunnan China", Annales Botanici Fennici, 40: 283-286.

Cho, J, and others (2007). "Hawaiian Kalo, Past and Future", University of Hawaii Cooperative Extension Service Bulletin, SA-1.

Colocasia Encyclopedia of Life. www.eol.org

Colocasia Floridata. www.floridata.com/ref/c/colo_esc.cfm

Colocasia International Plant Names Index. www.ipni.org

Long, C., and K. Liu, (2001). "Colocasia lihengiae (Araceae: Colocasieae), a new species from Yunnan, China", Bot. Bull. Acad. Sin, 42: 313-317

Misrta, R.S., Nedunchezhiyan, M., Suja, G. (2005), Commercially cultivated edible aroids in India, Aroideana 28: 174-190

Plant Delights Nursery Catalog -- Colocasia - www.plantdelights.com/Catalog/Current/

Tao, Y., Heng, L., ZaiFu, X., (2004), Colocasia menglaensis (Araceae), a new species from southern Yunnan China, Ann. Bot. Fennici, 41(3): 223-226

Whitney, Leo D., Bowers, F.A.I., Takahashi, M., (1939), Taro Varieties in Hawaii, Hawaii agricultural Experiment Station Bulletin no. 84

Yoshino, H. (1999), Phylogenetic general review of Colocasia and Alocasia based on the polymorphism of DNA and isozyme