Aloe is the name of a plant genus that contains more than 300 species. Most of the aloe species are native to Africa, Madagascar and the Arabian Peninsula. In addition to the familiar cactus-like plant called aloe vera that many people use to soothe sunburns and other skin ailments, this genus has plants that range from grassy succulents to large trees.
The tree aloe, or aloe barberae, is native to South Africa, Mozambique and Swaziland. It grows to 60 feet tall with a trunk up to 10 feet in diameter. It sports 1-1/2-inch red flowers with green spots during the winter months. Aloe arborescens is another aloe species that grows in dry regions of South Africa and also grows into a tree. Aloe pillansii, or "bastard quiver tree," is another South African aloe that can grow to 30 feet tall. It looks like a tall cactus or dracaena and grows in very arid regions. Another tree variety is the aloe dichotoma, or "quiver tree," which is one of the largest of the aloes.
Aloe vera is the star of the Aloe genus that many people know for its gooey sap that can soothe a sunburn in minutes. It is included in many commercial skin remedies and has strong economic significance. Aloe vera is the best aloe to use for medicinal purposes, since other member of the genus can have toxic properties. Aloe vera is suited for use as a houseplant and does well in lower light and dry conditions. It is frost tender, so it needs protection from the cold.
Poisonous or Toxic Aloes
Aloe venenosa and Aloe barbadensis both contain poisonous juice inside their leaves. Aloe venenosa and aloe barbadensis grow to 2 feet tall with a spread of up to 3 feet. These species contain a compound called aloin, which was used in laxative products until 2003, when the U.S. Food and Drug Administration banned it. These two poisonous aloes come from Africa, are frost tender and drought tolerant. They will withstand full sun or part shade in hot areas. These Aloes are suited to growing in the Southern and Southwestern United States and parts of the California and southern Oregon coasts.
Aloes That Deter Predators
Aloe ferox, also known as cape aloe, and several other aloe species have bitter properties that, when applied correctly, can help to repel certain predators. Aloe ferox helps contribute to a lucrative industry in South Africa. Indigenous people of South Africa used aloe ferox for its laxative, wound healing and anti-arthritis properties. Aloe ferox can grow to 9 feet and is a single-stemmed plant from South Africa that resembles an agave. Leaves are dull green, sometimes having a red tinge. It is found in open spaces as well as areas with shrubs and bushes. Like many other aloes, it is frost tender and thrives in dry areas.
Cold Hardy Aloes
Several species of aloe are frost tolerant and can live in conditions that are nearly alpine. Aloe aristats, aloe polyphylla and aloe striatula are landscaping possibilities for areas with cold winters. Aloe polyphylla grows at 6,000 to 8,000 feet in elevation and can survive some snow. This aloe has a spiral growth habit and is popular in wet, cold English gardens. Hardy aloe, the aloe striatula, hails from the eastern cape of South Africa and grows to 6 feet tall. It tolerates cold temperatures and dry weather.