This species is only occasionally tree-like (up to 5 m) and is more often a dense bush or rambling shrub in wooded spots or scrub.

Num-nums can also form a focal point with their ornamental foliage, flowers and fruit. Natural environments with frequent fire regimes result in low-growing forms. These plants have cultivation potential for use as borders in formal gardens. This species can also be used to provide neat hedges in parking areas.

C. macrocarpa deals well with salt-laden winds, making it a good choice for coastal areas.

Young plants need to be sheltered from cold for the first years as a precaution. The plants need moderate watering and grow in semi-shade to full sun. They are excellent for windy areas as the plants are wind-resistant. Plants are moderately drought-resistant but rather frost-tender and therefore best suited to the warmer parts of the interior and coastal plains as they are very tolerant of sea breezes.

Plants should be spaced approximately a metre apart to form an impenetrable hedge - they are well armed with thorns. They can also be used as ornamental plants in an informal border. Carissa bispinosa should be planted in light, well-drained soil with the addition of plenty of compost. It can be lightly pruned to keep it neat.

Leaves are opposite, simple, shortly petiolate, ovate, broadly ovate or ovate-elliptic, with a smooth margin, glossy dark green above, paler below, with short, thorn-like tips (heart-shaped tapering to a sharp point).

Pruning the plant is beneficial because it induces the development of more fruiting tips. Beyond cutting, little pruning work has to be done to restrain the bush from massive growth. This results in an increasing amount of fruits per plant.

Plants produce attractive flowers that may attract birds, insects (especially butterflies) and even monkeys to your garden.

Flowers are small, white or tinged pink, with a long, slender corolla tube, sweetly scented and clustered at the tips of twigs.

Night-flying insects pollinate the white, bisexual flowers.