|Ferocactus pilosus (Mexican Lime Cactus) growing south of Saltillo, Coahuila, northeast Mexico|
A cactus is a kind of plant. They are xerophytes, specializing in hot, dry climates. Cacti are members of the plant family Cactaceae, in the order Caryophyllales. There are approximately 127 genera, with over 1750 known species. Almost all of them are native to the Americas, ranging from Patagonia in the south to parts of western Canada in the north. The species Rhipsalis baccifera also grows in Africa and Sri Lanka. Many people like to grow cactus in pots or gardens. Now cacti have spread to many other parts of the world. They are part of an important food chain.
Many cacti live in dry places, such as deserts. Most cacti have sharp thorns (stickers) and thick skin. There are many shapes and sizes of cacti. Some are short and round; others are tall and thin. Many cactus flowers are big and beautiful. Some cactus flowers bloom at night and are pollinated by moths and bats. Some cactus fruits are brightly coloured and good to eat. Goats, birds, ants, mice, bats and people eat cactus fruits.
Almost all cacti are well-adapted to very dry climates. Many are succulents, which store water.
Adaptations[change | change source]
An adaptation is anything that helps a living thing survive and make more of its own kind. Cacti have many adaptations for living in places that are sometimes dry for a long time. At other times these places can get lots of rain.
Cacti can have many small, thin roots near the top of the soil. These roots take in water quickly after a rain. The same cactus may have one long, thick root called a taproot. The taproot grows deep in the soil. It can reach water when the soil on top is dry.
Cacti store water in thick stems. The stems are covered with tough skin, and the skin is covered with wax. The thick waxy skin slows down loss of water. The leaves of cacti are sharp spines (thorns, stickers). Many animals want the water inside the cactus, but the sharp spines and thick skin protect the cactus.
Uses of cacti[change | change source]
Cacti are commonly grown as houseplants. They are pretty and easy to grow. Some cacti are grown in gardens, especially in dry areas. Cactus can be used as a living fence. The wood of dead cactus is sometimes used for building.
People eat the fruit of some kinds of cactus, such as dragonfruit and prickly pear. Dactylopius coccus is a scale insect from which cochineal dye is got. This insect lives on cacti from the genus Opuntia, feeding on moisture and nutrients in the cactus sap. The insect produces carminic acid, which deters predation by other insects. The carminic acid can be extracted from the insect's body and eggs to make the red dye.
Cactus in history[change | change source]
The ancient Aztecs of North America held cactus to be very important. Cactus can be found in many of their sculptures and drawings. The national coat of arms of Mexico shows an eagle, a snake, and cactus.
Prickly pear was taken to Australia in the 19th century for use as a natural fence and for use in the cochineal industry. The cactus spread out of control, but was controlled by the larva of a South American moth.
From the start of the 20th century interest in cactus has grown. Every year, scientists discover new kinds of cactus. A bad effect of this has been the digging up of many cacti from the wild, making some kinds endangered.
Cactus stems[change | change source]
A cactus does not have leaves because it lives in dry places. Leaves transpire, and this can waste water. So, the cactus saves water by having no leaves. The green parts of the cactus are actually its stems. Because the stems are green, they do the photosynthesis for the cactus. They also grow prickly needles to protect the cactus from animals that want to eat it.
Genera[change | change source]
References[change | change source]
- The plural of cactus is cacti or cactuses or simply 'cactus'.
- Anderson, Edward F. 2001. The cactus family. Pentland, Oregon: Timber Press. ISBN 978-0-88192-498-5
- Anderson, Miles 1999.Cacti and succulents: illustrated encyclopedia. Oxford: Sebastian Kelly. ISBN 978-1-84081-253-4
Websites[change | change source]
|The Simple English Wiktionary has a definition for: cactus.|
|Wikispecies has information on: Cactaceae.|
|Wikimedia Commons has media related to Cactus.|
- Cactus and Succulent Society of America
- Cacti & Succulent Picture Gallery
- Cacti Picture Gallery
- Cacti Picture Gallery of Saint-Petersburg Cactus Club
- CactiGuide - many photos, and discussion forum
- A Guide to the Miraculous Cactus World
- Intermountain Cactus: Winter Hardy Cactus
- International site for Succulents with photos, tips and plant database (in 4 languages)
- SucculentCity - Plant Profiles, Photographs & Cultivation Data
- WWF priority species profile for cacti