The Hawaiian Islands do not have any native cacti, although numerous species have been brought in for usage as ornamental plants, reputedly from Acapulco, Mexico, in the early 19th century.
Cacti can be found on Maui.
I spent the majority of my work as an earth scientist in the American West’s deserts, where species of tree-sized cactus are common. It follows that I naturally began to believe that “giant cactus” only existed in arid sand deserts on North American soil. Imagine my shock and perplexity when, on Maui, a tropical island in the middle of the Pacific Ocean, with more than 300 inches (760 centimeters) of annual rainfall, I came upon hundreds of thickets of a fairly huge type of cactus, the Prickly Pear.
East Maui’s Ho’okipa Beach is home to a mature prickly pear cactus that is growing on a rock face there.
Opuntia ficus-indica, also known as “Panini” in Hawaiian, was first introduced to the Hawaiian Islands in the early nineteenth century, reportedly as cattle fodder, but it has now become a native of all the principal islands. Although it is not uncommon to see giant adult plants cling to nearly vertical cliff sides, particularly in dry leeward coastal locations, it loves sunny open terrain on mild slopes. This species of Opuntia prefers rocky, well-drained soils with a pH range of 7 to 8.5 because these soil characteristics promote root growth and branching. Additionally, it can survive on somewhat salinized soils and in air that is between minus 6 and 65 degrees Celsius.
A mature prickly pear cactus that resembles a tree is growing in a cattle field on Pulehu Road in south Maui. more than 10 meters in length, horizontally! [Image: click for a larger version.]
At maturity, the gigantic segmented cactus known as the prickly pear can grow to heights of three to five meters with a lateral span of two to three times that height (usually at 20 years of age). The individual leaves of this plant, known as “pads or “nopales,” are edible but are coated in widely spread aureoles that have one to six 1-3 cm long white or yellowish spines. In addition to these powerful spines, glochids, which resemble microscopic hairs but are no less powerful than conventional spines, are abundant in aureoles. Unsafe handling of the prickly pears’ pads and fruit can result in many of these small spines getting stuck in the handler’s skin and soft tissues, where they can stay for days or weeks and frequently get infected. The considerable woody stem of the tree is made of old pads.
This species’ fruit, which is also known as “tunas or “pears,” is normally greenish white to yellow, yellowish brown, or reddish-purple in color (depending on the strain). At maturity, individual fruits are roughly 10 cm long and half that wide, and they are juicy and barrel-shaped. Similar to the pads, the delectable nopales have glochids in their aureoles and need to be handled with care and prepared correctly before eating.
A prickly pear cactus with a “nopale (leaf) with multiple fruits (“tunas”) growing in a cattle pasture on Pulehu Road, south Maui.
Insects pollinate the flowers of the prickly pears. They have a cup-like shape, are vivid yellow or orange, and have a diameter of 5-7 cm. They develop along the edges of distinct pads and bloom in the spring or first part of the summer.
South Maui’s Pulehu Road, prickly pear cactus flower [click on image to view a larger version].
Birds, feral pigs, and lizards that eat the fruits also spread the seeds. After extended rainy periods followed by months of hot weather, the seeds from whole fruits and animal droppings begin to sprout. Although seeds in the soil might live for many years. Cladodes (flattened succulent segments and stems), which fall near to parent plants and readily take root, are used in vegetative reproduction. The latter type of reproduction frequently produces dense stands of numerous, big plants.
Pulehu Road in south Maui, showing a healthy nopale of a prickly pear cactus [click on image to get a larger version].
Don Francisco de Paulo Marin most likely brought Opuntia ficus-indica from Mexico to Hawaii in or around 1809. Its inherent flaws kept it from becoming well-liked by ranchers despite being originally meant to serve as a fence in cattle pastures, cattle fodder, and a source of food for humans (*panini is Hawaiian for “fence wall”). This species, if grown in the incorrect environment, has the potential to become a dangerous weed that can take over cow grazing areas and eventually wreck them with its invasive overgrowth. Additionally, it might displace some local flora and disturb ecosystems. By 1910, prickly pear cactus had been planted on thousands of acres of pastureland. Although only the spineless types were first developed, through genetic recombination and selective grazing pressure, the species gradually returned to the spiny wild genotype. There were significant Prickly Pear invasions in numerous nations over a span of roughly 200 years (including the Hawaiian Islands).
[Click on image to view a larger version] New bud developing on the tip of a “nopale of a Prickly Pear Cactus.
Biological Surveillance
Prickly pear cactus once came dangerously close to engulfing Maui and the nearby islands. Due to its propensity to quickly spread outside of its initial cultivation zones, the plant is regarded as a nuisance species. Cactus infestations were such a serious environmental problem that extensive biological control measures had to be started. The tunneling larval caterpillar of the Argentinean cactus moth (Cactoblastis cactorum) was shown to be the most efficient biological control agent. Early in the 20th century, releases of the caterpillar in Australia (where Opuntia ficus-indica infestations most severely damaged the environment) resulted in practically total eradication of the species. Cactoblastis was brought to Hawaii in 1950 as a result of its success in Australia.
A cactus moth (Cactoblastis cactorum) larval caterpillar considering its next meal. South Maui’s Kula. [Image: click for a larger version.]
The larvae of Cactoblastis cactorum consume the entire cactus plant by digging communally into the fruits, pads, stems, and root system, devouring the entire biomass from the inside out and leaving nothing above ground. Even if the caterpillar only partially preys on the cactus plant, the accompanying tissue damage encourages the spread of bacteria and fungi, hastening the plant’s demise. The larvae of the cactus moth are capable of obliterating entire cactus stands. On the island of Hawaii’s Volcano National Park, they were planted in an invasive stand of prickly pear cactus in 1985, thus removing the risk of an adverse invasion. In the western slopes of Maui’s Haleakala volcano, there are currently a lot of solitary stands of Opuntia ficus-indica, particularly in the vicinity of the villages of Pukalani, Makawao, Kula, and Ulupalakua. Although there are a lot of cactus here, most of them are in bad shape since moth larvae have been preying on them.
Medical and Pharmaceutical Applications
The Prickly Pear Cactus has some redeeming qualities despite its well-deserved reputation as an invasive species and noxious weed: recent laboratory studies have revealed that extracts of the plant’s various parts have significant medicinal benefits and are potential sources of raw material for the pharmaceuticals industry.
Fruit from prickly pears contains antioxidants.
Oxidative stress happens when a cell’s ability to defend itself fails. Oxidative stress is caused by an imbalance between oxidants and antioxidants, an overabundance of oxidants, and/or a deficiency in antioxidants. A significant amount of new data points to the importance of oxidative stress in a number of features of acute and long-term cellular and tissue inflammation. According to studies by the U.S. Department of Agriculture, fruits like blueberries, cranberries, raspberries, strawberries, apples, and prickly pears have significant levels of antioxidants that reduce inflammation. According to studies, betalains, a group of red and yellow pigments produced from indoles that are present in plants like the common beet, support the antioxidant and free radical-scavenging functions of prickly pear fruits. Only one plant species, the prickly pear cactus, is known to possess all 24 of the known betalains, a class of uncommon and effective therapeutic antioxidants. Many severe inflammatory disorders in humans are treated with these antioxidants. They might also aid in encouraging tissue and organ recovery as well as easing the more unpleasant symptoms of an alcoholic hangover. Not terrible for a weed, is it?
Visit the website “How to Eat Prickly Pear Cactus” first if you intend to try your hand at making Prickly Pear tunas and nopales for your dinner table. It includes very thorough directions for getting rid of the glochids and their double-nasty spines. If you eat fruits that you have prepared yourself, PLEASE BE CAREFUL! Try them at a real Mexican restaurant where they know how to make these bad boys, that’s my recommendation!