The Num Num plant, botanically known as Carissa macrocarpa and commonly called Natal Plum, is a subtropical evergreen shrub native to the coastal regions of South Africa. This resilient species is prized for its ornamental value, featuring glossy, dark green foliage and fragrant white, star-shaped flowers. The plant yields a deep red, plum-like fruit that is edible when fully ripe, tasting somewhat similar to a cranberry or slightly unripe cherry. Due to its dense growth habit and tolerance for harsh conditions, it is frequently used as a protective hedge or a groundcover in landscaping.
Climatic Requirements and Hardiness Zones
The Num Num plant thrives in warm, moist subtropical and tropical environments, which dictates its narrow range for reliable outdoor cultivation. It is generally suitable for year-round growth in USDA Hardiness Zones 9b through 11, where average minimum winter temperatures remain above 25°F (-3.9°C). Established plants can briefly survive temperatures as low as 25°F, but young plants are more sensitive and require protection below 30°F (-1°C).
The plant’s ideal growing temperatures range from 65°F (18°C) up to 100°F (38°C). Prolonged exposure to temperatures near or below freezing will cause significant damage, affecting foliage and potentially killing branches. In colder climates outside of Zone 9b, cultivators must grow Carissa macrocarpa in containers, allowing the plant to be moved indoors or protected during winter months to avoid frost damage.
Light and Sun Exposure Needs
Optimal growth, flowering, and fruit production in the Num Num plant depend heavily on receiving sufficient sunlight throughout the day. The shrub shows a distinct preference for full sun exposure, which is defined as a minimum of six hours of direct, unfiltered sunlight daily. This high light intensity promotes the densest foliage and ensures the most abundant set of the distinctive red fruit.
While full sun is preferred for maximum yield, the plant exhibits good tolerance for partial shade conditions. Growing in reduced light will result in sparser foliage and a noticeable decrease in the quantity of both flowers and subsequent fruit. In extremely hot and arid environments, a few hours of afternoon shade can actually be beneficial, helping to protect the plant from the most intense heat of the day.
Soil Composition and Drainage
The success of the Num Num plant is highly dependent on the physical structure and drainage capacity of its planting medium. While the species is highly adaptable and can tolerate a variety of soil types, it absolutely requires excellent drainage to prevent root issues. Waterlogged soil is the main enemy of this shrub, as prolonged saturation can quickly lead to root rot and plant stress.
It can thrive in poor, sandy, and even coastal soils, which is consistent with its South African coastal origins. Although it tolerates less-than-ideal conditions, the plant performs best in a well-drained loamy soil that is moderately fertile. The preferred soil reaction is slightly acidic to neutral, with an acceptable pH range spanning from approximately 6.1 to 7.5. Its natural resilience also extends to high salt tolerance, making it an excellent choice for landscaping near the sea.
Water Availability and Irrigation
A key characteristic of the Num Num plant is its substantial drought tolerance, a feature that makes it popular in xeriscaping and low-water landscapes. Once the shrub is fully established in the ground, its watering needs are minimal, and in some climates, it may not require any supplemental irrigation at all. This is due to its thick, leathery leaves, which efficiently reduce water loss through transpiration.
Newly planted specimens require a different approach to establish a strong root system. During the first year, it is necessary to provide moderate, consistent watering to encourage deep rooting. For established plants, the general rule is to allow the soil to dry out almost completely between deep waterings to avoid the development of root rot. The frequency of irrigation will vary seasonally, requiring more water during hot, dry periods and when the plant is actively setting fruit, while watering must be significantly reduced in the cooler winter months.