Xerarchs of the Cactus Kingdom Quiz

Answer: Arizona

The striking saguaro cactus (Carnegiea gigantea) is a native of the Sonoran Desert, which covers a large part of Arizona, as well the western part of the Mexican state of Sonora. Famous for its distinctive shape - a column-like trunk with branches known as arms, all covered in very sharp spines - the saguaro can grow to a height of 16 m (52.2 ft), with a diameter of up to 75 cm (30 in). Saguaros grow slowly, but are also long-lived, some of them reaching over 200 years of age. In the spring, they produce large white flowers, which in June turn into edible, ruby-red fruits.

This iconic xerophyte, a symbol of the American Southwest, provides not only food, but also nesting space to a number of bird species. When fully grown, it is also able to absorb huge amounts of water during rainstorms, allowing the plant to survive very long periods of drought.

The saguaro owes its generic name to industrialist Andrew Carnegie; the "gigantea" refers to the cactus' impressive size. Damaging any of these plants in any way is illegal in Arizona, where the Saguaro National Park was established in 1994 in order to protect this species; the saguaro blossom is also Arizona's state flower.

Answer: nopal

Prickly pears belong to the genus Opuntia (named after the Ancient Greek city of Opus) of the cactus family. Like the vast majority of cacti, these succulents are native to the Americas, but have been successfully introduced to other parts of the world. The most common (and most important in terms of its practical uses) species of Opuntia is the Indian fig (Opuntia ficus-indica), which is grown as a crop plant in many of the world's arid and semi-arid regions.

"Nopal", the name given to these plants in Spanish, comes from the Nahuatl "nohpalli", denoting the cactus' distinctive, fleshy pads (cladodes), which grow out of a central trunk. In Mexico, nopales are eaten as a vegetable, and are part of many traditional dishes. The fruits ("tuna" in Spanish, "fico d'India" in Italian) need to be harvested with care because they are covered in tiny spines; they are an important source of water in arid regions, and rich in vitamin C. In Sicily, the Indian fig grows almost everywhere, and its fruits are used to make various sweet treats, such as "granita" (a kind of coarse-grained water ice).

The opuntia cactus is depicted on the Mexican coat of arms, providing a perch for the eagle at its centre.

Of the three wrong answers, jícama and chayote are also vegetables widely used in Mexican cuisine, though neither of them comes from a cactus. Piñon, or pinyon, refers to the edible seeds of some species of pine, grown both in southwestern North America and the Mediterranean region.

Answer: tequila

The various species of agave (from a Greek word meaning "illustrious") are recognizable by their fleshy, blade-like leaves arranged in a distinctive rosette shape. Like other succulents, they are natives of the hot, dry regions of the Americas, but now grow in other parts of the world with similar characteristics - such as South Africa and the Mediterranean. Popular as ornamental plants in regions where water is scarce, some species of agave are also grown for their practical uses. Agave sisalana is a source of sisal, a natural fiber often used to make ropes and twine; agave nectar, a syrup-like sweetener, is derived from the sugar-rich sap extracted from agave flowers.

Though agave has traditionally been used for the production of alcoholic beverages such as pulque and mezcal, tequila is produced only with the sap of the blue agave (Agave tequilana). Blue agave plants, native to the highlands of the Mexican state of Jalisco, can grow to a height of 2 m (7 ft) and more. The spirit is named after the city of Tequila, whose red volcanic soil is perfect for the cultivation of the blue agave.

Answer: pineapple

Like most of the plants in the family Bromeliaceae (the bromeliads), pineapple is native to the tropical Americas. Though these plants are not exclusively found in arid or semi-arid environments, those that are have developed an adaptation - known as "tank habit" - that allows them to capture water and nutrients in a structure formed by their tightly overlapping leaves. The most economically significant bromeliad, the pineapple (Ananas comosus), generally grows in more humid environments (such as Hawaii or Costa Rica), but, like the other members of its family, carries out a process known as CAM (crassulacean acid metabolism) photosynthesis, in which the pores (stomata) in the plant's leaves remain closed during the day to reduce transpiration, and open at night to collect carbon dioxide.

Many bromeliads have beautiful, variegated leaves with interesting patterns, and are relatively easy to grow, which makes them popular as ornamental plants. The native peoples of Central and South America have used these plants (not just the pineapple, which was introduced to Europe and Asia by the Spanish and Portuguese) for centuries, both as sources of food and for other practical purposes.

Piña colada is a well-known cocktail made with pineapple juice, coconut milk and rum.

Answer: Kalahari

Cucumis metuliferus belongs to the family Cucurbitaceae, and is closely related to cucumbers and melons. Its fruits are distinguished by hard, yellow-orange rind studded with horn-like spines - hence the plant's common name of "horned melon"; the pulp is green and jelly-like, with lots of small seeds and a refreshing taste. The horned melon, like its relatives, is a vine, endemic to the semi-arid regions of central and southern Africa, where it grows wild at low to medium elevations. This rather alien-looking fruit is a traditional food for the African peoples who live within its range, and is especially important as a source of water during the dry season for the inhabitants of the Kalahari Desert. Outside of Africa, the horned melon - which has a long shelf life, and is very resistant to diseases - is also cultivated for ornamental purposes.

The name "kiwano", originally trademarked in the 1980s by two New Zealand exporters, comes from the resemblance of the fruit's pulp to that of the kiwifruit.

Of the deserts listed as incorrect choices, Danakil is located in East Africa (Ethiopia, Eritrea and Djibouti), Taklamakan in China, and Atacama in South America.

Answer: Brazil

The stately, long-lived carnaúba palm (Copernicia prunifera) is native to northeastern Brazil, a region of the vast South American country largely covered by the Caatinga ("white forest" in the indigenous Tupi language), a desert vegetation characterized by small, thorny trees and other xerophytes. This palm, adapted to withstanding long periods of drought, can grow to a height of 20 m (65.6 ft). Its products are very valuable to the inhabitants of this challenging environment: all parts of the tree can be used for different purposes, from food (for humans and livestock) to fibers and wood. However, the carnaúba palm is mainly cultivated for the wax extracted from its beautiful, fan-shaped leaves. Surfboard wax is made by mixing carnaúba wax with coconut oil, and many different kinds of polish employ this substance - prized for its high-gloss finish - as an essential ingredient; it is also used in the pharmaceutical industry as a coating for tablets.

Because of its economic and cultural importance, the carnaúba palm has been adopted as one of the symbols of the northeastern Brazilian state of Ceará.

Of the three incorrect choices, Ecuador is the only country that, like Brazil, is located in South America and for the most part in the Southern Hemisphere; it cannot, however, be described as large.

Answer: dragon

The genus Dracaena (from the Greek word for "female dragon") includes many popular, low-maintenance houseplants. These plants, related to agave (Q. 3), are native to tropical and subtropical regions of the world. The best-known species of treelike Dracaena are the Canary Islands dragon tree (Dracaena draco) and the Socotra dragon's blood tree (Dracaena cinnabari). The latter is only found on the islands of the Socotra Archipelago, which belongs to Yemen, though it is closer to Somalia and geographically part of Africa. Because of their climate and isolation, these islands are home to a staggeringly high number (around 700) of endemic plant and animal species.

The dragon's blood tree is successfully adapted to its harsh environment. Its unique shape resembles an umbrella held upright, with leaves growing in rosette-like clusters at the end of each branch; this uniquely-shaped crown provides shade and reduces evaporation in the island's hot desert climate. The tree's dark red resin, known as dragon's blood, was highly sought after in ancient times, especially for medicinal purposes; it is still harvested today, mostly to be used as varnish for violins.

Unfortunately, human activity and climate change are threatening the survival of this unique tree, which looks like something out of a science-fiction movie. Because of these challenges, the species has been classified by IUCN as Vulnerable (2004).

Answer: acacia

Acacia aneura, a tree of the family Fabaceae, is native to the Australian outback, where it grows extensively; its common name "mulga" comes from an Aboriginal language, possibly Yuwaalaraay. Like all Australian acacias, it is thornless, and well adapted to its arid environment: its needle-like phyllodes (leaf stems) are particularly effective at minimizing water loss, and its roots penetrate deep into the soil to find moisture. Generally small and shrub-like, mulga trees can live for hundreds of years. Used for centuries by the Aboriginal populations for its wood and other products, mulga is a very important source of fodder for livestock.

The habitat named after these trees - a savanna-like mix of woodland and grassland - covers about 20% of the interior of the Australian continent. Other species of Acacia are also found there, as well as the characteristic tussock grass known as spinifex (Triodia). Various animal species have also been named after the mulga habitat - notably, the mulga parrot (Psephotellus varius), and the mulga snake, or king brown snake (Pseudechis australis).

Of the three wrong answers, aloe is a succulent native to the Arabian Peninsula; alder is a tree of the birch family; and araucaria is a conifer of the Southern Hemisphere.

Answer: it is poisonous

Nerium oleander belongs to the family Apocynaceae, which bears the rather ominous common name of "dogbane" - a warning of sorts about the poisonous nature of many of these plants. In its wild state, oleander grows as a shrub (as shown in the picture, taken in a dry river valley in Libya), but is often trained into a small tree when cultivated for ornamental purposes. This plant, thought to be native to the Mediterranean basin (where it is widespread), has also been introduced to North America; it thrives in warm climates, and can tolerate long dry spells. Oleanders are prized as ornamental plants for their beautiful, five-lobed flowers - white, pink or red - and glossy, dark-green leaves; they also like hot sunlight, and animals tend to leave them alone because of their bitter taste.

Oleander contains various chemical compounds (known as cardiac glycosides) that are toxic to certain animals, including dogs and humans. Though rarely fatal, at least to adults, oleander poisoning can be rather unpleasant, so it is a good idea to be careful around the plant - also because its sap can cause allergic reactions such as dermatitis (no sneezing, though). Oleander flowers are often fragrant, and the plant does not have any thorns.

Answer: wormwood

Artemisia californica, the California sagebrush, is a member of the same genus as wormwood (Artemisia absinthium), the plant used as a flavouring for absinthe and vermouth, synonymous with bitterness: in the Book of Revelation, Wormwood is the name of a star that will turn one-third of the world's waters bitter. Most of the plants belonging to this genus contain powerful essential oils that discourage animals from feeding on them.

California sagebrush is endemic to the ecoregion of the west coast of North America known as California chaparral and woodlands - characterized by plants compatible with a Mediterranean climate (mild, wet winters and hot, dry summers). It is a shrub that can reach a height of 2.5 m (8 ft), with flexible stems and grey-green leaves; because of its pleasant smell, it is used as a seasoning in cooking. The Native American inhabitants of the region also used this plant for various medicinal purposes: indeed, its high content of flavonoids and terpenoids make it an effective anti-inflammatory and pain reliever. California sagebrush is also widely grown as an ornamental plant.

The word "chaparral" comes from the Spanish "chaparro", meaning "dwarf evergreen oak". In the Mediterranean region, similar plant communities are called "maquis" or "macchia", and the three plants mentioned as wrong answers are all found there.