Aloe marlothii is a striking, robust, large, single-stemmed aloe with a majestic presence. The mountain aloe is without doubt one of southern Africa's most rewarding aloes to grow and adds an interesting slant to aloe culture.Aloe marlothii is a large, perennial, succulent, single-stemmed aloe, usually 2-4 m tall (occasionally up to 6 m), with old dried leaves remaining on the stem below the upper living leaves. Leaves are large, broad and succulent, light green to greyish green to blue-green, up to 1500 x 250 mm, having a broad base tapering to a sharp point, covered with spines on upper and lower surfaces and maroon- coloured teeth with orange tips along leaf margins.
Flowers are held on racemes on a branched candelabra-shaped inflorescence, having up to 30 racemes (single spikes covered with individual flowers). Flower colour varies from the typical orange-red to yellow or bright red and may be present between May and September. The distinguishing character lies in the slanted inflorescences. They are usually almost horizontal but may be almost vertical in some forms.