Aloe is a succulent plant in the genus containing over 500 species of flowering succulent plants. Also written Aloë, the most widely known species is Aloe vera, or “true aloe”, so called because it is cultivated as the standard source of so-called “aloe vera” for assorted pharmaceutical purposes.
Other species, such as Aloe ferox, also are cultivated or harvested from the wild for similar applications.
The Aloe species was first described by Carl Linnaeus in 1753 as Aloe perfoliata var. vera, and was described again in 1768 by Nicolaas Laurens.
The first known written reports on the nourishing juice of the aloe vera plant reach as far back as 6,000 years ago in ancient Egypt. Aloe was regarded as a sacred plant the “blood” of which held the secrets to beauty, health, and immortality.
Both Cleopatra and Nofretete greatly valued the nourishing juice and used it as a part of their daily skin and beauty care.
The usage of aloe was regarded as the pursuit of physical beauty. Even the dead were embalmed with aloe vera because of its anti-bacterial and anti-fungi qualities.
The common belief was that in stopping the physical decomposition process eternal life could be attained, both on a physical and a spiritual level. Aloe was known as the “plant of eternity”. It’s anti-inflammatory and pain soothing effect was documented in the “papyrus Eber” of 1,550 BC.
Most Aloe species have large, thick, fleshy leaves. Aloe flowers are tubular, frequently yellow, orange, pink, or red, and are borne, densely clustered and pendant, at the apex of simple or branched, leafless stems.
Some species of Aloe appear to be stemless, with the rosette growing directly at ground level; other varieties may have a branched or unbranched stem from which the fleshy leaves spring. They vary in color from grey to bright-green and are sometimes striped or mottled. Some aloes native to South Africa are tree-like (arborescent).
The genus is native to tropical and southern Africa, Madagascar, Jordan, the Arabian Peninsula, and various islands in the Indian Ocean (Mauritius, Réunion, Comoros, etc.).
A few species have also become naturalized in other regions (Mediterranean, India, Australia, North and South America, Hawaiian Islands, etc.).
In the past, it has been assigned to the family Aloaceae (now included in the Asphodeloidae) or to a broadly circumscribed family Liliaceae (the lily family). The plant Agave americana, which is sometimes called “American aloe”, belongs to the Asparagaceae, a different family.
More recently, the APG IV system places the genus in the family Asphodelaceae, subfamily Asphodeloideae. Within the subfamily, it may be placed in the tribe Aloeae.
Over 500 species are accepted in the genus Aloe, plus even more synonyms and unresolved species, subspecies, varieties, and hybrids.
Some species are:
- Aloe aculeata Pole-Evans
- Aloe africana Mill.
- Aloe albida (Stapf) Reynolds
- Aloe albiflora Guillaumin
- Aloe arborescens Mill.
- Aloe arenicola Reynolds
- Aloe argenticauda Merxm. & Giess
- Aloe bakeri Scott-Elliot
- Aloe ballii Reynolds
- Aloe ballyi Reynolds
- Aloe brevifolia Mill.
- Aloe broomii Schönland
- Aloe buettneri A.Berger
- Aloe camperi Schweinf.
- Aloe capitata Baker
- Aloe comosa Marloth & A.Berger
- Aloe cooperi Baker
- Aloe corallina Verd.
- Aloe dewinteri Giess ex Borman & Hardy
- Aloe erinacea D.S.Hardy
- Aloe excelsa A.Berger
- Aloe ferox Mill.
- Aloe forbesii Balf.f.
- Aloe helenae Danguy
- Aloe hereroensis Engl.
- Aloe inermis Forssk.
- Aloe inyangensis Christian
- Aloe jawiyon S.J.Christie, D.P.Hannon & Oakman ex A.G.Mill.
- Aloe jucunda Reynolds
- Aloe khamiesensis Pillans
- Aloe kilifiensis Christian
- Aloe maculata All.
- Aloe marlothii A.Berger
- Aloe mubendiensis Christian
- Aloe namibensis Giess
- Aloe nyeriensis Christian & I.Verd.
- Aloe pearsonii Schönland
- Aloe peglerae Schönland
- Aloe perfoliata L.
- Aloe perryi Baker
- Aloe petricola Pole-Evans
- Aloe polyphylla Pillans
- Aloe rauhii Reynolds
- Aloe reynoldsii Letty
- Aloe scobinifolia Reynolds & Bally
- Aloe sinkatana Reynolds
- Aloe squarrosa Baker ex Balf.f.
- Aloe striata Haw.
- Aloe succotrina Lam.
- Aloe suzannae Decary
- Aloe thraskii Baker
- Aloe vera (L.) Burm.f.
- Aloe viridiflora Reynolds
- Aloe wildii (Reynolds) Reynolds
- In addition to the species and hybrids between species within the genus, several hybrids with other genera have been created in cultivation, such as between Aloe and Gasteria (×Gasteraloe), and between Aloe and Astroloba (×Aloloba).
History Of Aloe
The earliest documentation of Aloe was discovered on the clay boards from Nippur which date back as long ago as 2,200 BC. The people of this era were already aware of the cleansing effect of aloe on the intestines, in this period of history illnesses were always regarded as demonic possession of the body and only a divine plant such as aloe had the natural power to exorcise the demons.
In the times of Alexander the Great, aloe vera was commonly used for medicinal treatment in the countries of Asia. It is documented that Alexander the Great employed the use of aloe juice to heal the war wounds to his warriors (356 – 323 B.C.)
Alexander went to the extent of having transportable carts of planted Aloe for practical reasons in order to have fresh supplies at the ready during his numerous battle campaigns.
It is said, that Aristotle convinced Alexander the Great to capture the Island Socotra specifically to gain possession of the precious aloe groves in doing so Alexander acquired sufficient medication to heal the wounds of his entire battalions.
To their benefit, the Romans followed the wisdom of the Egyptians and Greeks by also using the healing powers of the aloe vera plant.
During the reign of Emperor Nero in around 50 B.C. the physician and naturalist Dioscorides journeyed the whole of the orient researching new methods of medication. He wrote several books teaching on pharmaceutics which included many prescriptions for the treatment of countless illnesses.
In his extensive chapters based on the positive effects of plant therapy, he describes the aloe as one of his favourite healing plants. He recommended the use of aloe juice for numerous physical disorders such as the treatment of wounds, gastrointestinal discomforts, gingivitis, arthralgia, skin irritation, sunburn, acne, hair loss, etc.
In Chinese culture, aloe has been an important ingredient in medical treatments since the times of the Marco Polo expeditions.
The treatment book of Shi- Shen described aloe vera as the “Method of Harmony”- the plant played a major role in the everyday life of the Chinese.
The Japanese culture also greatly values the aloe plant, in Japan, it was known as the “royal plant”, the juice was consumed as an elixir and the samurai used it for embrocations.
Around 1100 and during the middle-ages, does Hildegard of Bingen, a benedictine-nun, describe Aloe as a cure for icterus, gastric-infections, and migrain, against caries and for saniouse uclers.
According to Rudolf Steiner, the aloe represents the moon in conflict with the sun – relating to the high liquid content of the plant. The main characteristic is the tension between the ethereal and the astral.
A special facet of the aloe plant is its ability to organize the water, to maintain life and to reproduce (numerous offshoots!) in dire conditions: heat, wind, dryness.
Due to its robust outer layer and its myriad webbed inner vein system, the aloe manages to maintain its moistness by preventing evaporation; it is a truly remarkable survivor of nature.
Priest Kneipp was a great admirer of the aloe vera, in both plant and powder form. Kneipp was overwhelmingly convinced of the purifying and detoxifying effect on the digestive system.
The intestine and the intestine-associated immune system played a major role in the treatments of Kneipp. It is also reported that Kneipp had great healing success when applying the aloe to both infective and degenerative ailments of the eye.
New worlds were discovered with the aid of aloe vera, Christopher Columbus was known to have aloe vera growing in plant pots on his armada of ships and the plant was used to heal the wounds of his mercenaries.
During the 16th century, Spanish Jesuit monks – harvested the wild aloe vera and were known to spread the plant it in areas where it had not yet been cultivated.
Today these monks are still renowned as well educated phytologists and healers. The Maya Indians christened the highly resourceful juice of this desert plant as the “Fountain of Youth”.
During the 16th century, the Indian tribes also became familiar with the aloe healing plant. Aloe was one of the 16 holy plants which were worshiped with god-like status.
The diluted aloe juice that they applied to their skin worked as an insect repellent protecting them on their exhausting marches through the infested swamp areas. The Indians also used the aloe insect repellent on wood and other vulnerable materials that were likely to be damaged by insects; this treatment preserved the materials with great effect.
Also famous is the elixir of the Swedish doctor Dr. Yernest who died in a horse riding accident at the ripe age of 104 years old. At the point of this accident, the recipe for the elixir had been a well-kept family secret for some years prior.
In the meantime, however, this secret has been disclosed to the whole world. The elixir which is known today as Swedish Bitters is composed of practically the same ingredients: An ounce of aloe, a gross each of zedoary root, gentian root and the best of saffron, a gross of fine rhubarb root, a gross of larch fungus, a gross of theriac venetaian all mixed with a pint of good quality brandy, let brew for ten days and then filter. Back then the good Swedish doctor assured us: “take 7 to 8 drops of this remedy every morning diluted in wine, tea or bouillon and this will guarantee longevity without the need of bloodletting or a doctor. The remarkable thing is that this remedy is good for everything.”
In Sanskrit, aloe is known as Ghrita-Kumari. Kumar means girl and it was believed that this plant supplied the energy of youth to women and had a rejuvenating effect on female nature. In the Indian ayurvedic medicine, aloe is applied in numerous applications such as rejuvenating remedies, for menorrhea problems and to stabilize the cardiovascular system. Aloe is regarded as the plant of balance between pitta, kapha and vata – the aloe is one of the very few plants that hold these qualities!
Aloe species are frequently cultivated as ornamental plants both in gardens and in pots. Many aloe species are highly decorative and are valued by collectors of succulents. Aloe vera is used both internally and externally on humans as folk or alternative medicine. The plants can also be made into types of special soaps or used in other skin care products (see natural skin care).
Numerous cultivars with mixed or uncertain parentage are grown. Of these, Aloe ‘Lizard Lips’ has gained the Royal Horticultural Society’s Award of Garden Merit.
Of the 500+ species, only a few were used traditionally as herbal medicines, Aloe vera again being the most commonly used species. Also included are A. perryi and A. ferox.
The Ancient Greeks and Romans used Aloe vera to treat wounds. In the Middle Ages, the yellowish liquid found inside the leaves was favored as a purgative.
Unprocessed aloe that contains aloin is generally used as a laxative, whereas processed juice does not usually contain significant aloin.
Some species, particularly Aloe vera, are used in alternative medicine and first aid. Both the translucent inner pulp and the resinous yellow aloin from wounding the aloe plant are used externally for skin discomforts. As an herbal medicine, Aloe vera juice is commonly used internally for digestive discomfort.
According to Cancer Research UK, a potentially deadly product called T-UP is made of concentrated aloe and promoted as a cancer cure. They say “there is currently no evidence that aloe products can help to prevent or treat cancer in humans”.
On May 9, 2002, the US Food and Drug Administration issued a final rule banning the use of aloin, the yellow sap of the aloe plant, for use as a laxative ingredient in over-the-counter drug products. Most aloe juices today do not contain significant aloin.
According to W. A. Shenstone, two classes of aloins are recognized. Nataloins, which yield picric and oxalic acids with nitric acidwhich does not give a red coloration as with nitric acid.
Added barbaloins, which yield aloetic acid (C7H2N3O5), chrysammic acid (C7H2N2O6), picric and oxalic acids with nitric acid may be divided into a-barbaloins, obtained from Barbados Aloe, and reddened in the cold.
As well as b-barbaloins, obtained from Aloe Socotrina and Zanzibar Aloe, reddened by ordinary nitric acid only when warmed or by fuming acid in the cold.
Nataloin (2C17H13O7·H2O) forms bright-yellow scales, barbaloin (C17H18O7) prismatic crystals. Aloe species also contain a trace of volatile oil, to which their odor is due.
Aloe perryi, A. barbadensis, A. ferox, and hybrids of this species with A. africana and A. spicata are listed as natural flavoring substances in the US government Electronic Code of Federal Regulations.
Aloe socotrina is said to be used in yellow Chartreuse.
All species of Aloe (except for A. vera L.) appear on CITES (Convention on the International Trade in Endangered Species of Wild Fauna and Flora).
Appendices, meaning that trade in aloes is controlled to prevent utilisation that would be incompatible with their survival.
A total of 21 species, including varieties of some of these species, are included in Appendix I and trade in specimens of these species is permitted only in exceptional circumstances. The other aloes are all on Appendix II and therefore certain permits are required to trade in these aloes.
In South Africa most aloes are also protected, with very few exceptions, by environmental legislation in all nine provinces. It is thus illegal to remove plants from their natural habitat without the necessary collecting and transport permits issued by a provincial or other nature conservation authority, and consent from the land owner.
In the latest Red List of South African Plants, a total of 46 aloes are listed as species of conservation concern: Critically Endangered: 5; Endangered: 4; Vulnerable: 15; Near-threatened: 10; Rare: 9; Declining: 1; Data Deficient –Insignificantly known: 2.
Common threats listed for the survival of these aloes are restricted distribution ranges, habitat destruction, and fragmentation, collecting for horticultural purposes, invasive alien encroachment, and harvesting for medicinal purposes.
Fortunately, the genus is well represented in ex-situ collections with 88% of all aloe taxa in three gardens, the Kirstenbosch, Karoo, and Pretoria National Botanical Gardens in South Africa.
The most common shape of flowers found in Aloe is tubular flowers, although some species have curved or even bell-shaped flowers.
Flowers are typically brightly colored and most often in various hues of red, orange and yellow, but there are also some species with green, pink or white flowers.
The vast majority of aloes flower in winter, while some groups, like the grass aloes for instance, usually flower in spring or summer.
Aloe fruit is capsules that dry out and split open to release the mature small, brown to black, angled seeds that sometimes have a narrow or prominent translucent or white wing. The wing is thought to aid wind dispersal of the seeds.
There are a group of ± 20 aloes from Madagascar and the Mascarene islands that have a fleshy berry, which does not dry out completely and become woody. These berried aloes are sometimes separated into the genus Lomatophyllum. and their leaves are generally not as succulent as those of other aloes.
Aloes are mostly long-lived plants, especially the larger species. A specific quiver tree (Aloidendron dichotomum) was estimated to be between 100-145 years old, while some exceptionally tall specimens (of over 10 m) of Aloe marlothii may even be over 200 years old.
Aloes are well-adapted to the often arid conditions found in their natural environment. Their succulent leaves enable them to survive prolonged periods of drought. Sharp thorns and spines, as well as usually bitter leaf sap, are good deterrents for many herbivores, although certain animals seem completely undaunted by these defence mechanisms of aloes and the juicy leaves are often eaten.
Aloes often occur in environments that are prone to regular fires. Several strategies exist through which plants survive these fires. Some aloes are resprouters; fires can completely kill the above-ground parts, but plants have a thick underground rootstock that resprouts.
Other aloes survive fires by growing in fire protected habitats; these are most often rocky outcrops, where the fire is not as severe as in the surrounding grassland vegetation. Many stemmed aloes retain their old dry leaves around their stem and this acts as an insulator against the heat of fires.
Brightly colored, tubular flowers that are filled with nectar are a welcome source of food during the winter. Aloe flowers are regularly visited by pollinating birds and insects, but also by pollen and nectar thieves (these can be insects, birds or mammals) that do little in terms of pollination; some can even destroy an inflorescence completely.
Seed: Propagating aloes from seed is relatively easy and germination usually starts within one week of sowing. Seed should be harvested as soon as the capsules are dry and start to split open.
A resting period is not required and the seed should be sown fresh if possible. In South Africa the best months to sow seed is from August to February. Use a mixture containing equal parts of sifted compost and coarse river sand, sow seed over the surface and cover with a very thin layer of soil or pure sand, followed by a layer of pea-sized gravel.
The gravel layer provides support for the emerging seedlings which have a very weak root system and are very tender during their first few months. In nature seedlings are usually found in the shelter and shade of Ã¢e~nurse’ or companion plants.
Try to imitate this by keeping the seedling trays in the shade. Seedlings can be transplanted once three true leaves have formed, usually after about a year.
Cuttings: Cuttings are a popular and reliable way of propagating tree and shrub-like aloes. Stem cutting should be allowed to dry in the shade for a few days or even weeks, and then planted in the intended spot in the garden. Leaving cuttings to dry before replanting allows for the wound to heal and dry. This much reduces the risk of fungal infection and eventual rotting of the entire cutting. Plants grown from cuttings will reach maturity faster than plants grown from seed.
Division: Suckering aloes that form large clumps of many rosettes can be propagated by splitting a clump into individual plants. Suckers and small plants should be removed from the mother plant with a sharp knife. These should also preferably be left to dry in the shade before planting, especially if the suckers do not yet have roots of their own.
Plants that already have roots can be planted into their required places or pots and will become established faster than rootless plantlets. As in the case of cuttings, plants grown from clump division will reach maturity faster than plants grown from seed.