How often should I water it?

Water deeply but infrequently, allowing the soil to dry out completely between waterings.

Can I grow it indoors?

It is generally too large and requires too much direct sun to thrive indoors long-term.

Plant guide

Mountain Aloe.

Aloe marlothii

Pronounced AL-oh mar-LOTH-ee-eye

Also known as Flat-flowered Aloe, Mountain Aloe, Transvaal aloe, tree aloe

mountain aloe — Photo by Rosemary Harrison (CC BY-SA) via iNaturalist

This is a striking, large succulent that grows as a solitary rosette. It is native to rocky slopes in southern Africa, where it stands out for its impressive size and texture. You will love how it adds a rugged, architectural feel to your garden.

Another photo of Mountain Aloe — Photo by Sunčana Bradley (CC BY) via iNaturalist

At a glance

Care level: Easy
Plant type: Succulent
Light: Full sun
Indoor light: Direct sun
Water: Every 14 to 30 days
Mature size: 10 to 15 feet tall
Growth rate: Medium
Hardiness: USDA 9 to 11
Bloom time: Mid winter to early spring

Care

Plant this aloe in well draining soil to prevent root rot. Watch for mushy leaves, which often signal that the plant is getting too much water. It thrives when given plenty of sunshine and minimal fuss.

Watering: Allow the soil to dry out completely between waterings.
Feeding: Feed with a balanced liquid fertilizer diluted to half strength during the growing season.
Pruning: Remove dead or damaged leaves at the base as needed to keep the plant tidy.
Repotting: Repot only when the plant becomes rootbound or outgrows its container.
Soil: Sandy, well draining cactus mix
Soil pH: 6.0 to 7.5
Temperature: -2 to 40°C
Humidity: 10 to 40%
Drought tolerance: High
Lifespan: Perennial, can live for several decades.
Deer and rabbits: High

Signs it needs repotting

Roots growing out of the drainage holes
Water sitting on the surface for too long
The plant becoming top-heavy and unstable

Safety

People: The plant contains aloin, which is a potent laxative and skin irritant.
Pets: This plant is toxic to cats and dogs if ingested.
Children: The leaves are lined with sharp, stiff spines that can easily scratch or puncture a child's skin.
Contact allergens: The sap can cause contact dermatitis in sensitive individuals.
Airborne allergens: The pollen may cause mild respiratory irritation in some people.
Edibility: The sap is not for consumption and can cause severe digestive distress if ingested.

How to identify it

Large, thick, spiny succulent leaves
Grey green to brownish leaf color
Prominent teeth along leaf margins
Tall, branched flower spikes held out horizontally
Solitary, tree like growth habit

Height: 2 to 4m
Spread: 1.5 to 2.5m
Leaves: gray-green, blue-green, evergreen
Flowers: orange, red, yellow, 2 to 3cm
Fruit: brown, late spring

Problems to watch for

Root rot · This occurs when the soil stays too wet for too long.
Aloe mite · These tiny pests cause abnormal, gall-like growths on the leaves.

By symptom

Plant problems by symptom

Check your mountain aloe from a photo

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Growing it

Propagation: seed, cuttings
When to plant: spring, early summer
Overwintering: Keep the plant dry during the winter months to prevent rot. If you live in a frost-prone area, move the container to a sheltered spot.
In containers: It can grow in a large, heavy pot, but it will eventually become top-heavy and require a very stable container.

Seed

1. Sow seeds in a well-draining sandy mix.
2. Keep the soil lightly moist until germination.
3. Provide bright, indirect light for seedlings.

Pair this plant with other drought-tolerant species that do not require frequent soil disturbance.

Grows well with

Blue Fescue · Its fine texture contrasts beautifully with the bold, spiky leaves of the aloe.
Sedum · These low-growing succulents provide a nice groundcover that shares similar water needs.

Similar species

Aloe ferox · It has a similar stature but its flower racemes stand erect like candelabras rather than spreading horizontally.

Science

Family: Asphodelaceae
Genus: Aloe
Order: Asparagales
Class: Liliopsida
Native range: Southern Africa, specifically South Africa, Botswana, and Zimbabwe.
Conservation: It is not currently endangered, but wild collection is strictly regulated in many areas.

It survives in arid, rocky environments by storing water in its thick, succulent leaves.

Value to wildlife: nectar source, nesting habitat
Pollinators: bees, butterflies, birds
Uses: ornamental specimen, xeriscaping, rock garden focal point

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 2/9
Soil reaction: 6/9
Light: 8/9
Temperature: 7/9
Moisture: 2/9
Nutrients: 3/9

Taxonomy resolved against GBIF.

Questions people ask

How often should I water it?: Water deeply but infrequently, allowing the soil to dry out completely between waterings.
Can I grow it indoors?: It is generally too large and requires too much direct sun to thrive indoors long-term.

Where the name comes from

The name honors Rudolf Marloth, a German-born South African botanist who documented much of the region's flora.

Good to know

It can grow up to 4 meters tall in ideal conditions.
The leaves are covered in small, sharp spines on both surfaces.
It is a very slow grower, often taking years to reach maturity.
The nectar is highly attractive to sunbirds in its native habitat.

Also in

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This guide was generated with AI on October 28, 2026 and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.