Aloe

Aloe is a massive genus of flowering succulent plants. It contains over 650 accepted species. These plants are classified in the family Asphodelaceae. They belong to the subfamily Asphodeloideae. Most species are succulents, meaning they store water in fleshy parts. They use enlarged leaves, stems, or roots to hold this moisture. This mechanism allows them to survive in very dry, arid environments.

The physical structure of most aloe species is quite distinct. They typically grow in a rosette pattern. A rosette is a circular arrangement of large, thick leaves. These leaves can be bright green or grey. Some varieties even show stripes or mottled patterns. Many species appear to be stemless and grow at ground level. However, other varieties grow from branched or unbranched stems. Some aloes from South Africa are even arborescent, which means they grow like trees.

Flowering is another key characteristic of the genus. Aloe flowers are usually tubular in shape. They often appear in colors like yellow, orange, pink, or red. These flowers grow in dense, hanging clusters called pendants. They are located at the apex, or the top, of the stems. These stems can be simple or branched.

Scientists have worked hard to understand how to group these plants. In the past, aloe was assigned to different families. It was once placed in the family Liliaceae, known as the lily family. It was also assigned to the family Aloeaceae. Modern systems like the APG IV system from 2016 place it in Asphodelaceae. Molecular phylogenetic studies since 2010 have changed how we view the genus. These studies suggested that the genus was not monophyletic. This means it did not include all descendants of a single ancestor. In 2014, researchers John Charles Manning and his team divided the genus into six distinct genera. These include Aloidendron, Kumara, Aloiampelos, Aloe, Aristaloe, and Gonialoe.

The history of human use for aloe is very long. The name "Aloe" likely comes from the Arabic word al'uluh. This term means a "bitter and shiny substance." It may also come from the Hebrew word ahalim.

Ancient Greeks and Romans used Aloe vera to treat wounds. During the Middle Ages, people used the yellowish liquid from the leaves as a purgative. This liquid often contained aloin, which acts as a laxative. However, the US Food and Drug Administration banned aloin in over-the-counter laxatives in 2002. Today, most aloe juices do not contain significant amounts of aloin.

Aloe vera is the most famous species in the genus. It is often called "true aloe" because it is the standard for many pharmaceutical uses. About 75% of all aloe species are used locally for medicinal purposes. Other important species include Aloe ferox and Aloe perryi. Humans use these plants for cosmetics and skin care products. They are also used in essential oils to help dilute solutions before skin application. Some species are even used as natural flavoring. For example, Aloe socotrina is reportedly used in yellow Chartreuse.

Beyond medicine, aloe has many cultural and ornamental roles. Many species are highly decorative and are collected by succulent enthusiasts. Some cultivars, like Aloe 'Lizard Lips', have won awards from the Royal Horticultural Society. In some cultures, plants like Aloe variegata were planted on graves. This was done because of a belief that it ensured eternal life. Some species have even been used to create hybrids. For instance, crossing Aloe with Gasteria creates a plant called Gasteraloe. Crossing Aloe with Astroloba creates a hybrid called Aloloba.