Aloe marlothii will grow easily and with very little care in most South African gardens and is recommended for gardens where the species occurs naturally. Bear in mind this is a summer rainfall species and therefore naturally thrives under warm wet summers and warm to cool, dry winters. Thus grown within its natural distribution range, plants may require less water care. In cultivation the species can tolerate additional watering in both summer and winter rainfall gardens and often as a result the species may appear quite different from the natural forms (i.e. leaves lighter green and less thorny). It is not necessary to deprive your specimens of water, only be aware that over-watering will steadily deteriorate their general health. Prerequisites for success include:

• Full sun-choose a warm spot. Rockeries are ideal for capturing extra heat.
• Watering-a sign of over-watering is over-inflated leaves, excessive over-watering will lead to rot. Under-watering results in thin, harder, less green leaves. Compensate accordingly. Water once a week for the first month following planting and reduce watering thereafter. Well-established plants can survive for several months without water. Be sure not to over-water in heavy clay soils.
• Well-drained soil-no strict soil mix needs to be adhered to for planting, however at least one fourth compost should be incorporated into the soil. One quarter river sand and one quarter compost mixed in equal quantities will improve drainage in heavy clay soils. If you are unable to provide your plant with regular watering, and the soil consists of heavy clay, plant directly. This method will however slow or even stunt the growth of the plant and may lead to rot. Bone meal can be added in generous quantities when planting.
• Size-realize this is a large aloe and needs room to grow.
• Position-planted in the correct position the mountain aloe makes a prize specimen. Plants can be used as living pillars along driveways or fences or less formally as scattered feature plants in the garden landscape.
• Pests and diseases-avoid planting near infected aloes or choosing infected nursery specimens. Look out for:
  • White scale is unsightly and can virtually cover the entire plant with a white-dotted, paint-like appearance. Control by scrubbing either with soapy water or soap and oil or nicotine sulphate and soap. As a last resort spray with a contact insecticide.
  • Aloe rust fungus forms black spots on the leaves and cannot be controlled by spraying. It is recommended that infected leaves are removed and plants kept healthy by feeding. Alternatively remove entire plants if severely affected.
  • Aloe cancer is caused by mites and leads to deformed leaves and inflorescences. It is best to remove the entire plant form the garden to prevent disease spread.
  • Snout beetles wreak havoc by burrowing into the stem and depositing their eggs and subsequent developing larvae. Larvae hollow out the stem leading to collapse of the plant. Treat by drilling a tiny hole in the stem and injecting systemic insecticide.

Aloe marlothii can be grown from seed with relative ease. Use a nursery seed tray, pot or any container with drainage holes. Fill the bottom of the container with a layer of stones and a thin layer of compost to ensure drainage and prevent soil escaping from the drainage holes. Sow seeds in spring, directly in river sand by evenly sprinkling the papery seeds over the surface. Cover seeds with a light sprinkling of sand (just enough to cover seeds). Water with a fine rose spray to prevent seeds and sand becoming displaced and place in a warm sunny position. Place under cover such as eves, cold frame or greenhouse in a well-ventilated position. It is important to use sterilized soil and containers to avoid disease setting in. To avoid seedlings damping-off from the wilting fungus, a preventative fungicide can be applied.

Water seeds of A. marlothii daily until germination, thereafter reducing watering to every few days. Do not water in the late afternoon or evening as this will promote damping-off. As the seedlings begin to show their succulence and aloe shape they require less watering, however they will develop faster with regular watering and care. Transfer seedlings at any stage from several months to two years into small pots with a more loamy soil mix. Place a layer of stone chip with a few centimetres of compost at the bottom of the pot. Various potting mixes work provided they are well drained (i.e. two thirds of soil comprising river sand and compost and one third nursery potting mix or rose and shrub mix). Liquid organic fertilizers will improve general vigour and resistance to disease attack.