Carissa edulis (Small Numnum): Complete Shrub Growing Guide
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Carissa edulis
1. Introduction & Taxonomy
The simple-spined num-num brings edible berries and formidable thorns to gardens across warm regions, where it serves equally well as security barrier, wildlife plant, and fruit producer. Native to Africa from Ethiopia to South Africa, this rugged shrub has fed people and protected homesteads for millennia with its sweet-tart berries and impenetrable thorny structure. Modern cultivation values both its practical applications and its tolerance of difficult conditions where more refined shrubs struggle.
(Description coming soon) Appearance Growth Rate Fast Growth Form ShrubClimber Ornamental Value Breathtaking Uses Properties ColorfulEvergreenFloweringScent Hazards Spiny Gardening FenceHedgeLandscapingOrnamental Food/Medicinal BeverageEdible FruitMedicinal
Taxonomic Classification
Habitat and Distribution
Carissa edulis is native to tropical and subtropical regions. This species inhabits environments typical of the Apocynaceae.
Botanical Note: A large family of flowering plants including many ornamental and medicinal species. Notable for often producing milky latex and frequently showy, tubular flowers. Includes desert succulents (Adenium, Pachypodium), tropical flowering shrubs, and important medicinal plants.
Native Range & Distribution Map
The map below shows the native range and notable cultivation regions for Carissa edulis.
2. Biology & Morphology
Growth Form & Architecture
Carissa edulis is an evergreen broadleaf shrub maintaining dense, lustrous foliage year-round. This dependable greenery provides consistent structure and privacy in the landscape.
Flowers & Reproductive Structures
Shrub flowers vary enormously across families, from tiny wind-pollinated catkins to large, showy insect-pollinated blooms.
Key Characteristics
- Height: 1-3m
- Growth Habit: Erect Shrub
- Growth Rate: Moderate under optimal conditions
- Life Cycle: Perennial
3. Reproduction & Propagation
Primary propagation methods for Carissa edulis: Cuttings, seed, or layering (varies by species).
Propagation Methods
Semi-hardwood cuttings taken in late summer. Layering for difficult-to-root species. Seeds may need stratification.
Propagation Tip: Wound the base of cuttings and use rooting hormone for best results.
4. Cultivation Requirements
Soil / Substrate
Rich, well-draining soil with organic matter. Many prefer slightly acidic conditions (pH 5.5-6.5).
Watering
Consistent moisture during growing season. Mulch to retain soil moisture.
Light Requirements
Full sun to partial shade. Most ornamental shrubs perform best with at least 4-6 hours of direct light daily.
Temperature
- Optimal Growth: 18-30°C (65-86°F)
- Minimum Tolerance: -12°C (10°F)
- USDA Hardiness: Zones 8-11
Pruning
Light pruning after flowering. Can be formally clipped for hedging. Remove dead or diseased wood anytime.
Fertilization
Apply a balanced slow-release fertilizer in spring. Most shrubs are moderate feeders.
Common Cultivation Mistake: Over-watering is the most common cause of shrub failure. Ensure good drainage and match watering to the species' natural habitat.
Seasonal Care Calendar
Follow this season-by-season guide for optimal care timing throughout the year.
🌱 Spring (March–May)
Apply compost or balanced fertilizer if desired, though plant thrives without feeding in poor soils. Prune to shape if needed (wear heavy gloves!). Water regularly during establishment. Flowers begin appearing as temperatures warm.
☀️ Summer (June–August)
Flowering and fruiting peak in warm season. Maintain moderate moisture for better berry production, though established plants survive drought. Harvest berries as they turn dark purple-black. Monitor for rare pest problems.
🍂 Fall (September–November)
Continue harvesting berries into fall in warm climates. Reduce watering as growth slows. Prune if desired to maintain hedge shape or control size. Collect seeds from berries if propagating.
❄️ Winter (December–February)
In frost-free climates, remains evergreen and may continue some flowering and fruiting. In areas with light frost, may experience leaf damage. Protect from temperatures below 25°F. Minimal care needed; avoid overwatering during cooler months.
5. Diseases & Pests
Carissa edulis is generally robust and pest-resistant when cultural conditions are optimal.
Major Diseases
Root Rot (Phytophthora, Pythium)
Caused by overwatering or poor drainage. Ensure good drainage and avoid waterlogging. Improve soil aeration.
Powdery Mildew
White powdery coating on leaves. Improve air circulation, avoid overhead watering, and apply fungicide if severe.
Leaf Spot (various fungi)
Brown or black spots on foliage. Remove affected leaves, improve airflow, and avoid wetting foliage.
Common Pests
- Scale Insects — Hard or soft scales on stems and leaves; treat with horticultural oil
- Spider Mites — Fine webbing on undersides of leaves in dry conditions; increase humidity
- Mealybugs — White cottony masses at leaf axils; spray with soapy water or neem oil
- Aphids — Cluster on new growth; spray with soapy water or introduce ladybirds
- Whiteflies — Tiny white insects on leaf undersides; use yellow sticky traps
IPM: (1) Choose the right species for your conditions. (2) Maintain good air circulation and hygiene. (3) Monitor regularly and act early. (4) Use chemical controls only as a last resort.
6. Indoor & Container Growing
Carissa edulis can be grown in containers and brought indoors during winter in cold climates.
Container Selection
Use containers with adequate drainage holes. Choose pots at least 5 cm larger than the root ball. Plastic retains moisture longer; terra cotta dries faster.
Indoor Light
Place in the brightest available location. Most shrubs need at least 4-6 hours of direct or bright indirect light.
Container Success Key: Match your container medium to the species needs: free-draining for xerophytes, moisture-retentive for tropical species.
7. Landscape Use & Design
Carissa edulis is a versatile landscape plant offering structure, colour, and seasonal interest.
Design Applications
- Hedging & Screening: Dense shrubs for privacy, windbreaks, and boundary definition
- Foundation Planting: Soften building lines and define entrances
- Specimen / Accent: Showcase plants as focal points in the garden
- Mixed Border: Combine with perennials, grasses, and bulbs for year-round interest
- Topiary & Formal: Shape dense evergreens into geometric or sculptural forms
Companion Planting
- Perennials — Echinacea, Salvia, Lavandula for mixed borders
- Other Shrubs — Layer heights and textures for depth
- Grasses — Ornamental grasses add movement and contrast
- Ground Covers — Underplant with low-growing species for a finished look
Design Principle: Plant shrubs in groups of odd numbers (3, 5, 7) for natural-looking compositions. Repeat key species throughout the garden for cohesion.
8. Cold Climate Strategies
Carissa edulis tolerates cold to USDA Zone 8. Winter protection or container culture may be needed in colder areas.
Hardiness Thresholds
- USDA Zones: 8-11
- Minimum Survival Temperature: -12°C (10°F)
Overwintering Options
- In-Ground Protection: Apply 10-15 cm of mulch over the root zone before first frost. Wrap trunks of borderline-hardy species with fleece.
- Container Culture: Move potted plants to a frost-free garage, conservatory, or cold greenhouse for winter.
- Microclimate Selection: Plant against south-facing walls or in sheltered spots to gain 1-2 zones of extra warmth.
Winter Survival Rule: Most shrub losses occur from late frost after spring growth has started. Avoid premature uncovering.
Frequently Asked Questions
Are the thorns really that bad?
Yes, the thorns are extremely sharp and strong, capable of puncturing tires and causing painful injuries. Always wear heavy leather gloves and long sleeves when working near or pruning these plants. The thorns are what make it excellent as a security barrier—few people or animals will attempt to push through. However, this makes it unsuitable near play areas, walkways, or anywhere people might accidentally contact it.
What do the berries taste like?
Ripe dark purple berries have a sweet-tart flavor often compared to cherries or cranberries, with pleasant fruity notes. They contain milky latex that turns clear when fully ripe. Eat only fully ripe berries, avoiding green or red stages which are astringent and contain more latex. Fresh berries are best, though they can be made into jams or jellies.
How cold-hardy is this species?
Hardy to about 25-28°F for brief periods once established, making it suitable for USDA zones 9-11. Temperatures below 25°F cause increasing damage, with plants killed by hard freezes around 20°F. It's less cold-tolerant than the related Carissa macrocarpa (Natal plum) which survives colder temperatures.
Explore More Species
Discover related species in our Shrub Encyclopedia:
Summary & Key Takeaways
Carissa edulis, is a erect member of the genus Carissa (Apocynaceae), native to Worldwide.
Key Points to Remember:
- Propagation: Cuttings or seed
- Light: Full sun to partial shade for most species
- Substrate: Well-draining, moderately fertile
- Watering: Moderate — match to species needs
- Hardiness: USDA Zones 8-11, minimum -12°C (10°F)