Also Known As: Bottlebrush Aloe, Rosary Vine
Category: Large Clumping Aloes
USDA Hardiness Zones: 9b - 11
OverviewAloe rupestris is a robust fast growing mostly single stemmed tree aloe with very showy flowers. The Aloe species that in fact carries the moniker, Bottlebrush Aloe, is quite spectacular but is nowhere near as popular a garden plant as it should be, given its ease of growing. Gradually matures into a sturdy trunked tree aloe, topped by a spiraling rosette that produces Candelabra-like 4 foot stalks covered in a bright yellow-to-gold-to-red conical racemes in Winter.
DescriptionMature specimens of Aloe rupestris have a relatively thin, unbranched trunk on top of which sits a compact, spiraled, rosette of thick succulent, blue grey leaves. In habit it resembles the related A. thraskii and A. excelsa, which also produce rather top-heavy rosettes atop an unbranched trunk. The stem (trunk) is sturdy to support the leaf structure and can reach a height of up to 8 meters. Mature plants carry many dried leaves that cover the upper part of the stem, giving it a rather shaggy appearance. These help to protect the stem from fires and hot sun, and even though they are unlikely to face a fire within a garden setting, should not be seen as an untidy part of the plant in need of removal. Although they can grow to 8 meters it more commonly will grow to about 3 meters in cultivation. Leaves are stiff, long, narrow, moderately channeled, straight to slightly incurved, a deep dull green and incredibly armed with extremely sharp, often hooked red-brown teeth. This is among one of the most dangerous tree aloes to walk by (until leaves over your head)- will easily and readily tear off any exposed flesh brushed up against them. Leaves of the bottle-brush aloe spread out in a spiral formation, have a smooth surface and curve downwards (re-curved). Offsetting forms have been favored in cultivation. In its natural habitat Aloe rupestris grows in bushes or next to a tree which gives support during strong winds. Aloe rupestris has a spread-root-system the roots are somewhat fleshy.
FloweringWhat is remarkable about Aloe rupestris are its 1 or 2 candelabra-form inflorescences up to 1.25 meters (4 feet) tall above the leaf rosette that bear 6-15 or more erect, cylindrical racemes. In late winter to early spring appear the sturdy inflorescence bearing many bottlebrush-like spikes of flowers that start out as tight masses of bright yellow buds that burst open to become completely overshadowed by the brilliant orange-red, exerted stamens. When they open, bright reddish stamens extend far out, and give each raceme a fluffy 'bottlebrush' look. The blooms are not long lasting but an amazing display that looks more like a Banksia flower than an aloe when in full bloom. Aloe rupestris is probably the most fluorescent of all the tree aloe flowers. It looks like psychedelic bottle brush from a distance. The individual flowers begin as tight yellow buds that are packed densely on the racemes.
Origin / HistoryThe plant name 'rupestris' means 'growing in rocky places' and refers to its habitat. The Bottlebrush Aloe gets its common name from its distinctive and showy flowers. Aloe rupestris occurs naturally across the south-eastern summer-rainfall areas of Kwazulu-Natal Province, South Africa, as well as Swaziland and southern Mozambique. Within this range, it favors rocky areas in bushveld, sandy coastal forest, and hilly areas where it occurs on rocky ridges and slopes. The region is frost free and day temperatures reach around 38C. The species is not considered to be threatened in its habitat. Aloe rupestris is closely related to Aloe excelsa and Aloe thraskii. Aloe rupestris has been given tree status in South Africa and its national tree number is 30.3.
Care / CultivationAloe rupestris is easy to grow, requiring very little care. Plant in full sun in a well-draining soil and irrigate occasionally to regularly - this aloe can take it dry or with abundant summer irrigation, so long as the soil drains well. When watering allow soil to dry out between waterings. Though drought tolerant, regular Summer water will pay off in steady growth (expect a gain of 1-2' per year) - which may eventually require a bit of support for the stalk. It tolerates weekly watering in the summer; once a month, or not at all in the colder months of December and January. At least in California, this plant nearly always is a super aggressive off-setter, unlike any other in the tree aloe family. Aloe rupestris is susceptible to Mealy bugs and white scale. These plants do not like over watering or insufficient sun, both of which will lead to an increased susceptibility to disease. Aloe rupestris has fairly slender stems and can be a little top heavy, particularly when in bloom, so staking may be in order as it gets taller; in its natural habitat it grows in dense shrub thickets which provide support. Propagated almost exclusively by seeds planted in autumn, in trays of coarse river sand. They thrive in alkaline soils; ash and lime additions are useful. These are relatively fast growers, going from 8 inch seedlings to 5 foot tall plants in about 6-7 years.
Frost TendernessIt is also one of the hardier of the large aloes, tolerating temperatures down to at least 25°F with minimal leaf damage but it’s still best to avoid planting in areas with prolonged periods of frost.
Use in the GardenAloe rupestris has beautiful flowers and makes a welcome addition to any garden. In mild climates it can be cultivated outdoors for use in landscaping, preferably planting it in hot and dry gardens. Fairly fast and easily grown in warm temperate and tropical climates in USDA Zones 9 to 11. The Bottlebrush Aloe is well suited to rock gardens, and at the edges of forest, grassland and bushveld, and will take a little bright shade during a hot summer. It can be grown in large containers. It’s a great way to add evergreen, vertical fascination & dramatic mid-Winter color to your garden. Aloe rupestris is popular with birds, bees & butterflies who find it's flowers impossible to resist.
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