Plantbase

Botanical name:

Aloe arborescens

Common names:

Krantz Aloe, Torch Aloe (English); Kransaalwyn (Afrikaans); ikalene (Xhosa)
inkalane, umhlabana (isiZulu)

Synonyms:

Aloe mutabilis

Plant family:

Asphodelaceae (as-foh-del-AY-see-ee)
- Includes genera Aloe, Asphodelus and Kniphofia

Plant categories:

Shrubs; Cacti and Succulents; Non-herbaceous Perennials

SA tree no:

28.1

Zimbabwe tree no:

17

Name derivation & history:

The name aloe is from the Greek 'alsos' and refers to the bitter juice from the leaves of these plants. It is probably derived from the earlier Arabic word alloeh or the Hebrew word allal, both meaning bitter.

The Latin word arborescens means tree-forming or tree-like, and is a bit misleading in that this aloe is not really tree-like, but the name was originally applied to this species in reference to the stem-forming habit.

The common name krantz aloe refers to its habitat, a krantz being a rocky ridge or cliff.

Aloe arborescens is one of approximately 130 Aloe species native to southern Africa. It is possibly the most widely cultivated aloe in the world and can be seen grown in gardens in many cities around the world.

Leaf habit:

Evergreen

Height:

2 to 3 metres

Width:

1 to 2 metres

Has thorns

Plant shape:

A much-branched, multi-headed shrub 2 to 3 metres high.

Leaf description:

The simple, evergreen, succulent leaves are long ( up to 70 cm), narrow (7 to 8 cm), and taper to the apex. They are usually slightly sickle-shaped and the margin is lined with conspicuous pale teeth. Although normally a dull greyish-green to blue-green, they may turn reddish when exposed to cold or too much sun or in drought.

The leaves are arranged in attractive rosettes at the ends of the branches. The old, dead leaves remain on the plant below the rosette for a while before dropping off.

Spine or thorn description:

Pale teeth on leaf margins.

Flower description:

The large colourful flower spikes are borne in profusion during the cold winter months (May-July), brightening up a drab winter garden. Deep orange is the most common colour, but there are also pure yellow forms, and an unusual bi-coloured form of deep orange (almost red) and yellow. The inflorescence is usually unbranched, with two to several arising from a single rosette.

Flower colour:

Deep orange is most common, but varies from red to pure yellow or even bi-coloured

Flowering months:

May to July

Fruit description:

A green capsule, ripening to brown, with 3 compartments that contain many slightly winged seeds.

Bark or stem description:

Many branches carrying multiple heads.

Natural distribution:

This species is distributed mainly over the eastern, summer rainfall areas of the country. It has the third widest distribution of any aloe, occurring from the Cape Peninsula along the eastern coast, through KwaZulu-Natal, Mpumalanga and Limpopo province and further north into Mozambique, Zimbabwe and Malawi.

Habitat:

It is one of the few aloes that can be found growing at sea level right up to the tops of mountains. The krantz aloe is adapted to many habitats, but is usually found in mountainous areas where it favours exposed ridges and rocky outcrops. It is also found in dense bush.

Water requirements:

Waterwise (little water required)

Frost tolerance:

Semi-hardy to hardy (tolerates a fair amount of frost)

Light conditions:

Sun; semi-shade

Interaction with physical surroundings:

As with all the aloes, the flowers produce nectar and are attractive to many kinds of birds, in particular the small and colourful sunbirds, which flit from flower to flower in search of nectar. The flowers also attract bees.

The flowers are also a favourite food of the Grey Go-away Bird (Grey Lourie) and they often bend or snap the young inflorescence stalks as they clamber around eating the flowers.

Uses & Cultural aspects:

In many parts of South Africa Aloe arborescens is planted around kraals (domestic stock enclosures) as a living fence. It often happens that the position of old kraals can still be seen many years after they have been abandoned because the aloes persist. Cuttings intended for use as barrier plants are sold in muthi shops.

The Zulu people use the leaves of this plant, dried and pounded into a powder, as a protection against storms. Decoctions of the leaves are also used in childbirth and in treating sick calves. In the Transkei it is used for stomach ache and given to chickens to prevent them from getting sick. In the Orient, this aloe is grown in domestic gardens as a convenient first-aid treatment for burn wounds and abrasions. In fact it was only after it was used to treat irradiation burn victims of Hiroshima that its healing properties received attention from the West. Extracts from the leaves have been widely investigated since then and shown significant wound healing, anti-bacterial, anti-ulcer, anti-inflammatory, anti-carcinogenic, hypoglycaemic and also alopoeic activity. The leaves have also been found to have purgative properties and the leaf sap is reported to relieve x-ray burns.

Cultivation:

The krantz aloe is an easy and rewarding plant to grow, and is a popular garden plant in many countries. It enjoys full sun, well-drained, compost-enriched soil and can tolerate moderate frost but is sensitive to severe frost. It is fast-growing, and it will tolerate drought and neglect once established. It is grown mainly as an ornamental or as an accent plant, but is also an excellent and impenetrable hedge plant.

The krantz aloe is easily propagated from a branch or stem cut off, allowed to dry for a day or so until the wound has sealed, and then planted in well-drained soil or sand. They need not be rooted in any particular place and then transplanted, but can be placed directly into their permanent place in the garden. It is important to remember not to water the cuttings too heavily as over-watering may cause them to rot.

This aloe can also be grown from seed, sown in spring. Seed should take three to four weeks to germinate, and the seedlings must be protected from frost.

Aloe arborescens hybridises readily with other aloes.

Pests & diseases:

Aloe arborescens var Lutea (a rare yellow form).

Notes:

The species formerly known as Aloe mutabilis is now regarded as a synonym of Aloe arborescens. It is a cliff dwelling form with smaller, less branched rosettes and red & yellow bi-coloured flower spikes and is more evident on the high inland plateau of the northern provinces of South Africa. This cliff dwelling form of Aloe arborescens can be seen hanging from the cliffs alongside the waterfall at the Witwatersrand National Botanical Garden.

Although it is in fact a large much-branched shrub, Aloe arborescens has been allocated a national tree number (28.1).

References:

South African National Biodiversity Institute, South Africa.

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