Prickly Pear Cacti in Hawaii? Ouch!

I spent most of my career as an earth scientist in the deserts of the American West, where there are tree-sized cactus species everywhere. So it’s natural that I came to think of “big cacti” as growing ONLY in places like the arid sand deserts of mainland North America. Imagine my surprise and confusion when I encountered hundreds of thickets of a really large species of cactus, the Prickly Pear, on Maui, a tropical island in the middle of the Pacific Ocean that receives more than 300 inches (760 centimeters) of annual rainfall.

Mature Prickly Pear Cactus growing on cliff face near Ho’okipa Beach, east Maui.
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The Prickly Pear Cactus, Opuntia ficus-indica (“Panini” in Hawaiian*) was introduced (ostensibly as cattle fodder) to the Hawaiian Islands early in the nineteenth century but is now naturalized on all the main islands. It prefers sunny open land on gentle slopes, although it is not unusual to see large mature plants clinging to nearly vertical cliff faces, particularly in drier leeward coastal areas. It prefers rocky well-drained soils with a pH range of 7 to 8.5, soil conditions that increase root growth and branching in this species of Opuntia. It also tolerates moderately saline soils and air temperatures ranging from minus-6º C to a high of 65º C.

A very mature tree-like Prickly Pear Cactus growing in a cattle pasture on Pulehu Road, south Maui. Measured more than 10 meters horizontally!
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The Prickly Pear is a massive trunk-forming segmented cactus that typically reaches heights of 3 to 5 meters with a lateral span of two to three times its height at maturity (usually at 20 years of age). The individual leaves (“pads” or “nopales”) of this species are edible, but are covered with widely spaced aureoles that include one to as many as six white or yellowish spines 1-3 cm long. In addition to these formidable spines, aureoles include numerous glochids, tiny hair-like spines that are smaller than typical spines but no less formidable. Incautious handling of pads and fruit of the Prickly Pear can cause scores of these tiny spines to lodge in the skin and soft tissues of the handler where they can remain for days or weeks, often becoming infected. Old pads form the substantial woody stem of the tree.

A very mature tree-like Prickly Pear Cactus growing in a cattle pasture on Pulehu Road, south Maui. Measured more than 10 meters horizontally!
[ Click on image to view a larger version. ]

The fruit (“tunas” or “pears”) of this species is typically greenish white to yellow, yellowish brown, or reddish-purple (depending on the strain). Individual fruits are fleshy and barrel-shaped, and at maturity are about 10 cm long and half that wide. Like the pads, the tasty nopales possess glochids in their aureoles and must be carefully handled and properly prepared prior to consumption.

A “nopale” (leaf) with several fruits (“tunas”) of a Prickly Pear Cactus growing in a cattle pasture on Pulehu Road, south Maui.
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The flowers of the Prickly Pear are pollinated by insects. They are cup-shaped, bright yellow or orange, and 5-7 cm in diameter. They form on the perimeters of individual pads and bloom in spring or early summer.

Flower of a Prickly Pear Cactus, Pulehu Road, south Maui.
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Seeds are dispersed by birds, feral pigs, and lizards that feed on the fruits. The seeds from intact fruits and animal droppings germinate after long rainy spells followed by months of hot weather. However, seeds in the soil can remain viable for several years. Vegetative reproduction is accomplished by cladodes (flattened succulent segments and stems) falling close to parental plants and quickly taking root. The latter form of reproduction often results in dense stands of many large plants.

Healthy nopale of a Prickly Pear Cactus, Pulehu Road, south Maui.
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Opuntia ficus-indica was probably introduced into Hawaii from Mexico by Don Francisco de Paulo Marin in about 1809. Originally intended to serve as a barrier in cattle pastures (panini means “fence wall” in Hawaiian*), cattle fodder, and a human food source, its innate shortcomings prevented it from becoming popular with ranchers. Cultivated in the wrong place, this species can develop into a destructive weed: it can overrun cattle grazing lands, eventually ruining them with its invasive overgrowth. It also may out-compete certain native plants and upset local ecosystems. By 1910, several thousand acres of pastureland were under cultivation with Prickly Pear Cactus. Although only the spineless varieties were initially established, the species gradually reverted back to the spiny wild genotype by means of genetic recombination and selective grazing pressure. Over a period of nearly 200 years, there were serious invasions of Prickly Pear in many countries (including the Hawaiian Islands).

New bud growing on the tip of a “nopale” of a Prickly Pear Cactus.
[ Click on image to view a larger version. ]

Biological Control — At one time, Prickly Pear Cactus nearly overran Maui and the neighbor islands. The plant is considered a pest species due to its ability to spread rapidly beyond the areas in which it was originally cultivated. The environmental threat posed by invasions of the cactus became so grave that large-scale biological control programs had to be initiated. It was discovered that the most effective biological control agent was the tunneling larval caterpillar of the Cactus Moth (Cactoblastis cactorum), a species native to Argentina. Releases of the caterpillar in Australia (where Opuntia ficus-indica infestations most seriously affected the environment) in the early twentieth century led to almost complete control of the species. On the strength of the successes in Australia, Cactoblastis was introduced into Hawaii in 1950.

A larval caterpillar of the Cactus Moth (Cactoblastis cactorum) thinking about its next meal. Kula, south Maui.
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The larvae of Cactoblastis cactorum feed on the entire cactus plant, burrowing into the fruits, pads, stems, and root system where they live communally, devouring the entire biomass from the inside out, leaving nothing above ground. Even if the cactus plant is only subjected to limited predation by the caterpillar, the resulting tissue damage facilitates the growth of bacteria and fungi, hastening the destruction of the plant. The Cactus Moth larvae are capable of destroying entire stands of cacti. In 1985 they were introduced into an invasive stand of Prickly Pear Cactus in Volcano National Park on the island of Hawai’i, successfully eliminating the threat of a damaging invasion. Today there are many isolated stands of Opuntia ficus-indica in the upland mesic forests of the western slopes of Maui’s Haleakala volcano, especially in the areas surrounding the towns of Pukalani, Makawao, Kula, and Ulupalakua. The cacti are relatively abundant here, but most individuals are in poor condition due to predation by the moth larvae.

Medicinal and Pharmacological Uses — Despite its well-deserved reputation as a noxious weed and invasive species, the Prickly Pear Cactus does possess some redeeming characteristics: recent laboratory studies have shown that extracts of various parts of the plant have significant medicinal benefits and are potential sources of raw material for the pharmaceuticals industry.

Prickly Pear fruit possesses antioxidants – When a cell’s capacity to protect itself fails, oxidative stress occurs. Oxidative stress results from an oxidant/antioxidant imbalance, an excess of oxidants, and/or a depletion of antioxidants. A considerable body of recent evidence suggests that oxidative stress plays a major role in several aspects of acute and chronic cellular and tissue inflammation. U.S. Department of Agriculture studies have shown that fruits like blueberries, cranberries, raspberries, strawberries, apples, and the Prickly Pear contain high concentrations of inflammation-fighting antioxidants. Researchers reported that betalains (a class of red and yellow indole-derived pigments found in plants like the common beet) contribute to the free radical-scavenging and antioxidant activities of Prickly Pear fruits. The Prickly Pear Cactus is the only plant species that contains all 24 of the known betalains, which are also a class of rare and potent healing antioxidants. These antioxidants are used to treat many serious inflammatory diseases in humans. They may also prove useful in promoting healing of organs and tissues, as well as mitigating the more unpleasant symptoms accompanying an alcoholic hangover. Not bad for a noxious weed, eh?

A Postscript for DIYers
If you plan to try your hand at preparing Prickly Pear tunas and nopales for your dinner table, be sure to first visit the website “How to Eat Prickly Pear Cactus”. It contains very detailed instructions for removing the nasty spines and double-nasty glochids. Please, BE CAREFUL if you eat fruits you’ve prepared yourself! My advice: try them at a genuine Mexican restaurant where they know how to prepare these bad boys!

Malama pono!

The Cattle Egret: Hawaii’s Beautiful Invader

Most serious birdwatchers (myself included) will never forget the first time they saw a Cattle Egret in flight: they glide effortlessly at relatively low speeds with just a few economical strokes of their large and powerful wings, taking off and landing quickly with the grace and maneuverability of a light bomber plane. I saw my first egrets on the tidal flats of the east shore of San Francisco Bay near Alameda Island where I raced my sailboat as a teen. I never knew a bird so large could be so bright white!

A foraging Cattle Egret (Bubulcus ibis) poses for the camera without loosing track of its intended meal.
(Click on image for a larger version.)

Traveling and living abroad in later life, I saw them striding calmly among the tourists on the beaches of Caribbean islands, foraging in the salt marshes and tidal flats of the Red Sea’s eastern shores, roosting in the acacia trees and on the kopjes of the Serengeti Plain of Tanzania, striding hesitantly along the muddy shorelines of cattle ponds in Colorado, and hunting for bugs in the paths of groundskeepers’ gas-powered riding mowers on the newly-shorn lawns of Maui’s vast golf courses.

A bird in a hurry: a mature egret displaying breeding plumage.
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As a photographer, I’ve grown to appreciate this bird’s other attributes: it’s a large, bright-white bird with contrasting orange beak and legs, with its patches of caramel-brown breeding plumage, and its willingness to pose fearlessly for the cameras of appreciative humans. With so many of these photogenic birds on Maui and the neighbor islands, it’s hard to keep their snaps out of one’s photo gallery.

Cattle Egrets pick up a free meal by following landscape technicians wielding power mowers and hedge clippers, picking off wounded and stunned insects in their wake.
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A Cattle Egret doggedly searching for its next meal atop a freshly-trimmed hedge.
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So… here’s some stuff I read online about the species and some stuff I’ve learned by watching Maui’s own Cattle Egrets.

Interesting Stuff I Read Online

The Cattle Egret (Bubulcus ibis) is a member of the family Ardeidae (herons). B. ibis is the ONLY species in the monotypic genus Bubulcus. Not sure WHY there’s just one species of Bubulcus: either all the other species left town, joined other genii, or some slacker taxonomist got bored after naming just one species to this understaffed genus. Only in the field of taxonomy do you find a category with just a single item to populate it.

A mature adult Cattle Egret stalking insects as it lightly strides atop a Mountain Apple hedge in Wailea.
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This stocky, substantial-looking bird has a wingspan of nearly 40 inches (~100 cm). With its relatively short, thick neck and characteristic hunched posture, it stands about 25 inches tall (65 cm). It weighs only a bit more than one pound (~510 g). Its plumage is usually pure white, but during the breeding season, adult birds display prominent light-brown, caramel-colored patches on the neck and back (what I’ve seen on Maui); its legs and bill also turn bright orange. The irises of the bird’s eyes reportedly turn bright red as well, but I have never witnessed this on any in-season birds on Maui (see my photos). Immature birds share the white plumage of adults, but sport no mating plumage, although they do have a distinctive black bill.

This bird’s habitation range extends from the tropics and subtropics to the warm temperate zone. Because young birds tend to disperse thousands of miles from breeding and nesting grounds, and because adult populations may range from being wholly migratory to passage-migrant to wholly resident, this species has a geographically large range: approximately 10 million square kilometers (3.8 million square miles). Its global population is estimated to be between 3.5 and 6.5 million. For these reasons, the Cattle Egret is not considered an endangered or threatened species. Quite the contrary: the rapid expansion and establishment of the species over such a large global range has led to its official classification as an “invasive” species.

The Cattle Egret was first introduced to Hawaii in 1959. It is popular with cattle ranchers throughout the world for its role as a biological control of ticks, biting flies, and other cattle parasites, pecking the little nasties directly off the skin of stock animals. It was this perceived benefit to livestock that prompted local ranchers (with the help and blessing of the Hawaiian Board of Agriculture and Forestry) to release the species in Hawaii.

Stuff I Learned Watching Birds In The Field

I live in Kalepolepu, a quiet residential neighborhood in north Kihei. A lot of the small beachfront homes have good-sized lawns with fast-growing grasses, and the nearby beaches are covered with ‘Aki ‘aki grass (a tough variety of buffalo grass). Small lagoons, cut-off ponds of brackish water, and other artificial and natural wetlands dot the neighborhood. All of which makes an ideal habitat for legions of terrestrial insects, frogs, toads, lizards, and small freshwater fish… the main dishes on our cattle egrets’ collective menu. From early spring until late summer/early fall, large numbers of migratory egrets follow behind homeowners and landscape technicians riding their self-propelled lawnmowers, picking off grasshoppers and other lawn-loving insects wounded and stunned by the mowers’ blades. When that first course of the moveable feast is done, the birds fly off to the wetlands, ponds, and garden pools to nab toad and frog tadpoles, as well as mullet and other small bait fish that flourish year-round in their warm, well-aerated water.

At least on Maui, Cattle Egrets don’t spend much time foraging on beaches or in the intertidal zone. In 10 years I have only seen two egrets flying over the open water of Ma’alaea Bay (see my photo, below). For a species that is known to migrate vast distances over open ocean, Cattle Egrets don’t seem to regard the marine environment as anything but a barrier to be overcome on the way to their next meal on terra firma.

A rare bird, indeed: a solitary Cattle Egret struggles against a stiff headwind while crossing the open water of Ma’alaea Bay.

B. ibis has a reputation elsewhere in the world as a predator of other bird species: they eat the chicks and eggs of other shorebirds; they kill and eat other species of land birds exhausted from migration; and they chase the chicks of some species of terns, forcing them to disgorge their food. I’ve never witnessed this behavior or heard reports of it on Maui or the other neighbor islands. This may be because there is such an abundance of insect and reptile prey species that is readily obtainable without much of an expenditure of energy on the egrets’ part.

I believe the egrets come to Maui for the same reasons as all the other tourists: the weather’s warm and mild most of the year, and there’s plenty of places on the island to get a tasty meal and a good night’s sleep. So the human and bird tourists all agree: Maui na oka oi …”Maui is number one!” No argument there.

I gotta phase… Laters!

Kiawe (Prosopis pallida): Hawaii’s Tropical Mesquite

A couple of years ago I was photographing some volunteers at a Beach Cleanup Day at Kanaha Beach park near Kahului on Maui’s windward side. Part of the cleanup involved piling up some large tree branches that had been cut the day before by a Maui County tree-trimming crew. As I and the volunteers began stacking the cut limbs by the side of the access road for the County people to dispose of, a pickup truck full of locals hurriedly pulled up behind us. The driver asked if he and his boys could have all of the cuttings. The crew leader agreed as long as they took the entire pile with them. “No problem, bruddah! Dat’s Kiawe and it’s great for makin’ barbecue fire!” In an instant, the slash pile was thrown into the bed of the truck by its enthusiastic passengers. The truck then sped off down the dirt road, its occupants all waving happily as if it was double-pay day. In this way I was introduced to the Kiawe, Maui’s tropical mesquite tree.

A healthy mature Kiawe tree helping to stabilize the berm on Kealia Beach, Ma’alaea Bay, Maui.
(To view a larger version, click on image.)

Prosopis pallida is a perennial that belongs to the Mimosoideae subfamily (mesquite & mimosa) of the Leguminosae/Fabaceae family. It is commonly referred to by its Hawaiian name “kiawe” (pronounced “kee-AH-vay”). As with all other members of this family, it produces its seeds in pods referred to as “legumes”, hence the common name for the family.

The outer bark and foliage of the Kiawe tree.
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Physical Characteristics — Under ideal conditions, Kiawe trees can grow to be more than 30 m tall and form dense, continuous forest canopies (one of the few species of dry coastal trees to do so). However, they may also develop into gnarled, stunted bush-like trees in dry, wind-swept areas with poor soil such as those found in stabilized sand dunes and beach berms.

Leaves emerge from a common node on the twig, which changes direction often as it grows, giving it a corkscrew or zig-zag appearance when mature. The small, delicate-looking leaves (usually less than 2 cm long by a half a centimeter wide) are doubly compound with 3 to 4 pairs of stemlets branching from the main leaf stem. The twigs and branches include a fair number of very formidable thorns (see image below) notorious for drawing blood from careless beach-goers who seek out the Kiawe’s ample shade.

In the spring, small yellowish-green flowers are borne on long (8 to 15 cm) cylindrical spikes that give way to dense clusters of long (10 to 20 cm) yellowish-brown seed pods. The 10 to 20 seeds per pod (see image below) are encased in a sticky, sugary pulp.  The heartwood is dense-grained and hard, making it a favorite fuel for cooking fires on Maui and throughout the world. Generally, the root system is shallow, spreading out laterally; but in arid soils it easily develops a long taproot.

A typical Kiawe twig displaying its characteristically delicate foliage and very nasty thorns.

Kiawe seed pods fall from a single tree’s branches by the thousands, ensuring that many seeds survive & germinate.
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Introduction to Hawaii — Prosopis pallida is native to the arid coast of northwestern South America. In 1828 it was introduced to the Hawaiian Islands by Father Alexis Bachelot, the head of the first catholic mission to Hawaii. He planted a tree on the grounds of the Catholic Mission on Fort Street in Honolulu that he had raised from the seed of a Peruvian tree growing in the royal gardens of Paris. By 1840, the progeny of that single tree became the principal shade trees of Honolulu and were already spreading to the dry leeward plains on all of the neighbor islands, including Maui.

Growth Habits — A Kiawe seedling’s survival depends on receiving sufficient rainfall and sunlight (the seedlings do not tolerate constant shade) during the first few weeks after germination. The seedling can grow more than one meter in its first year under the right conditions. It will produce a strong and rapidly growing taproot system that can penetrate deep into even the hardest soils. Many old trees have been saved as garden and park trees during land development and have grown to large sizes with constant irrigation. Trees that grow on coastal plains where groundwater is shallow and abundant grow to be quite large, but they develop shallow root systems and windstorms can topple them easily. Once mature, growth is very slow compared to that of other trees under similar conditions. On windy or dry sites, Kiawe grows as a shrub or a small twisted tree only a few meters tall. Where it grows in strong trade winds, it is sculpted and shaped by the prevailing winds and lies along the slopes as a rounded bush. Although it is a coastal species, Kiawe is easily defoliated by the windblown salt spray of winter storms. Kiawe trees grows in areas where fire hazard is often extreme. Trees rarely survive slow-burning fires; they are usually killed outright by fire.

Invasive Habits — Once Kiawe was introduced to Hawaii it quickly became a pest species, invading, out-competing, and overwhelming native grass species and woody plants. It is a successful invasive species due to its ability to reproduce in two ways: production of large numbers of easily-dispersed seeds, and vegetative growth (by suckering) to create thick monotypic stands that shade out all other nearby plant species. It requires less than four inches of annual rainfall to establish itself and survive. It survives well in dry environments due to its extremely long taproot. It is so efficient at withdrawing moisture from soil that it can kill nearby plants by depriving them of water. It is often found growing in areas where other plants do not grow, such as sandy, dry, degraded slopes; salty soils; disturbed areas; and rocky cliffs.

A dense, continuous canopy of Kiawe trees growing along a beach front in the Kawalilipoa neighborhood of Kihei, south Maui.
(To view a larger version, click on image.)

Ironically, it is these very traits that have made Prosopis species so valuable in efforts to control soil erosion due to desertification in Africa and South Asia. Kiawe serves a similar purpose on islands such as Maui where beach erosion is a serious problem.

These well-established Kiawe trees rooted in the unstable sands of Kealia Beach protect a delicate intertidal marine habitat from the ravages of wind-blown sand and storm-driven waves.
(To view a larger version, click on the image.)

Hawaii’s Jungle Fowl: They can’t tell morning from midnight

Until this morning, like every other Maui kama’aina (long-time resident), I was convinced that the only really objectionable characteristics of our ubiquitous feral chickens (more correctly known as Red Junglefowl) was that they’re everywhere on the island and they crow (loudly and constantly) at any hour of the night or early morning hours.  Unfortunately, those “sweet little chickens” the malahini (tourists) so love to feed and photograph have turned to crime!

A family portrait: Jungle Fowl rooster, hen and two fledged youngsters: E. Lipoa Road, Kihei, Maui.
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While shopping at the outdoor farmers market in north Kihei, I noticed a hen and her clutch of eight chicks foraging along the ground amongst some empty fruit and vegetable boxes. Much to the joy of some tourists and other naive adults, the hen suddenly performed a VERY athletic standing broad-jump into a crate of ripe apple bananas, whereupon she proceeded to loudly tear off several individual fruits from their bunches and fling them to the ground in front of the appreciative chicks. The attending clerks were not amused, and they and I had to chase the offending parent bird and her piteously cheeping children out of the banana crate and onto the street.

Red Jungle Fowl, Gallus gallus, run wild on most of the main islands of Hawaii, where they frequently cross-breed with domestic fowl. Jungle Fowl may be the progenitors of modern domesticated chickens. They probably originated in Southeast Asia about 8,000 years ago. The Polynesian colonists brought them to the Hawaiian Islands, along with other domesticated livestock and plants (referred to as “canoe species”), on their large sea-going canoes. Over the years, enough junglefowl escaped and went feral to form a large population on all of the major islands. One popular theory that’s gained street creds locally is that many of the feral birds are the escaped offspring of the hundreds of fighting cocks bred for the ring. Though outlawed in Hawaii, cock fighting is still popular as an underground sport. The presence of so many illegal “backyard” breeders inadvertently loosing track of the offspring may account for the recent spike in the feral birds’ population.

Rooster standing guard duty at Kokee Park headquarters, Kaua’i.
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The Red Jungle Fowl belongs to the class Aves, order Galliformes, suborder Phasiani and family Phasianidae, which includes pheasants and partridges. It is indigenous (native) to Southwest Yunnan Province (China), Myanmar (AKA Burma), Thailand, the Malay Peninsula, Singapore, northern Sumatra, the north-western region of the Himalayas and northern India. Subsequently it was introduced to Africa, Australia, the Marshall Islands, Micronesia, the  Northern Mariana Islands, and the Palau Group, as well as Hawaii, where the birds flourish and breed in large numbers due to the absence of any of their natural predators.

In general, the male bird’s plumage is gold, red, brown, dark maroon, orange, metallic green and gray. Two characteristic white patches shaped like ears appear on either side of the head. These “ear patches”, as well as the greyish skin of their bare legs and feet, distinguish Red Jungle Fowl from other chickens. The male birds can measure up to 70 cm in length. Both sexes have a total of 14 tail feathers, but the rooster’s tail can grow to almost 28 cm in length. Additionally, the female bird tends to be leaner and more compact than her tame barnyard counterparts.Normally, the Red Jungle Fowl is herbivorous and insectivorous: they favor wild and domesticated seeds of any kind they encounter while foraging, while beetles and other earthbound insects fill out their menu.

Hen & rooster greeting visitors to Kokee Park headquarters, Kaua’i.
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Fertile eggs take about 20 days to gestate and hatch. Chicks are fully feathered by the fourth or fifth week, and are sexually mature by their fifth month (female birds mature a bit later than males). In the wild, Gallus gallus can live for as long as ten years, under ideal conditions.

Rooster and chick, E. Lipoa Road, Kihei, Maui.
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During their mating season, which is usually Spring and Summer (though the Hawaiian birds seem to be “at it” all year long), the male birds announce their presence with the familiar “cock-a-doodle-doo” call. This serves both to attract potential mates and to make other male birds in the area aware of the risk of fighting a breeding competitor. Unlike the myth of the “cock crowing at dawn”, the roosters in my immediate neighborhood start crowing at about 3 or 4 AM and don’t put a sock in it until well after sunrise, usually 8 or 9 AM. I sleep like the dead, and so am not bothered in the least by the morning symphony of 10 or more birds crowing their defiance at one another. However, some of my immediate neighbors are not similarly blessed with the gifts of nocturnal oblivion and tolerance toward poultry, and so have resorted to setting live-traps in strategic locations. Trapped birds are then removed to the outskirts of town or the nearest golf course to live out their lives disturbing someone else’s peace (and putting).

Maui’s Blue Morning Glory: Ipomoea indica

Before I moved here I never gave the Morning Glory a second thought: to me it was just a colorful but mostly innocuous ground cover on the beaches of California where I grew up. However, on a small island like Maui they are kind hard to ignore because there are so many of them and they are seemingly everywhere you look. From the high-tide line on most of our white-sand beaches to almost 4,000 feet up Haleakala’s volcanic slopes, their cookie-cutter-perfect flowers and massive amounts of foliage and choking vines spill out over the landscape, engulfing everything from derelict automobiles to the headstones in cemeteries.

Flowers & foliage, the Blue Morning Glory, Ipomoea indica.
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The Morning Glories are plentiful in the Hawaiian Islands for two reasons: (1) they are able to adapt to almost any environment and (2) they propagate like oversexed rabbits. Their roots can absorb large quantities of seawater, they tolerate almost any kind of soil, and though they may be torn to shreds and small pieces they are still capable of taking root and flourishing. They choke off the saplings of competing species and shade-out established trees and bushes. On the other hand, Morning Glories can be important pioneer species that stabilize sand dunes and prevent beach erosion.

A solitary blossom of Ipomoea indica.
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The Blue Morning Glory (Ipomoea indica)

Ipomoea indica is a perennial vine native (indigenous) to Hawaii (“koali awa” in Hawaiian). It is variously known as Ocean Blue Morning Glory, Blue Morning Glory, and Blue Dawn Flower. It’s also called a “Dunny Creeper” in Australia (a “dunny” is an outhouse toilet), referring to its habit of covering everything in sight with its vines, including small out-buildings. Its geographic origin is uncertain: it may be native to the West Indies. It is now naturalized throughout the tropics and is found on all the main Hawaiian Islands. It is usually found at lower elevations (below 200 m) but has been known to grow at altitudes above 1,200 m.

Close-up of a mature Ipomoea indica plant. Note the characteristic 3-lobed leaves.
(Click on the image to see a larger version.)

Ipomoea indica prefers sunny open ground in a moist environment, but will tolerate seasonal dry spells once it is well established. It is a perennial that grows as a sprawling (ground-hugging) vine that produces a dense ground cover, but it is often seen climbing and twining over other plants. The vine itself (called a “stem”) is softly hairy and may grow to more than seven meters in length. The distinctively shaped leaves are large (as much as 15 cm wide and 17 cm long) and numerous. They may be heart-shaped when immature; mature leaves are 3-lobed to 5-lobed with pointed tips. The upper and lower surfaces of the leaf are covered by silky, short, closely-spaced hairs.

The flower is large (as much as 80 mm in diameter) It usually ranges in color from sky blue to purple-blue; less commonly it may also be light magenta and reddish-pink. It has paler mid-petal bands and a pink to whitish tube inside. The petals (3 to 15 per flower) are joined, which accounts for the distinctive trumpet-like shape of the flower. Ipomoea indica sets flowers all year, continuously flowering during warmer months. The short-lived flowers are replaced as they fall from the vine.

The fruit is a small (about 10 mm in diameter) 3-chambered spherical capsule. These are rarely produced by the plant. It has almost no self-fertilization and so grows vegetatively: its preferred method of propagation is by the production of numerous stolons, stems that grow above ground and are able to produce both roots and foliage. Individual stolons are readily detached from the parent plant and dispersed by mechanical means such as flooding, stream flow, landslides, or human activity (ground clearing and weed removal). Even when badly damaged, a plant can easily recover 4-6 m of its length in a single growth season. One theory about why Ipomoea indica evolved this unique reproductive behavior is that the species is a sterile hybrid and its genes are self-incompatible.

This species contains toxic alkaloids (including Ergonovine, which bears a strong molecular resemblance to Lysergic Acid Diethylamide, or LSD) that discourage ingestion by grazing animals. This defense mechanism contributes to its prevalence as a weed species.

Photo shows the tendency of the Blue Morning Glory to choke off sunlight from other plants by spreading its tendrils and vines in all directions, wrapping itself around anything from tree trunks to derelict automobiles.
(Click on image to see larger version.)

The Blue Morning Glory is a vigorous climbing vine that not only forms a dense ground cover but can easily extend itself high into the forest canopy. The twining stems can quickly choke off the growth of seedlings of other species and smother even older well-established plants. It also poses a significant shading hazard to other species.