Ultimate Guide to Summer‑Flowering Bulbs in South Africa (2025‑26)
Ultimate Guide to Summer-Flowering Bulbs in South Africa (2025–26)
Last updated: 25 September 2025
Welcome to the most comprehensive, South Africa-specific handbook on summer-flowering “bulbs”. Whether you garden on a coastal balcony in Durban, a Highveld smallholding near Johannesburg, or a Mediterranean courtyard in the Western Cape, this guide will help you choose the right species, plant at the right time, and enjoy months of colour and fragrance.
Quick definition: Gardeners often say “bulbs” but we also mean corms, tubers, rhizomes and tuberous roots—storage organs that power seasonal growth.
Table of Contents
- Understanding South African Climate Zones
- Soil Preparation & Site Selection
- Summer Bulb Planting Calendar
- Bulb Basics: Bulb vs Corm vs Rhizome
- Top 20+ Summer-Flowering Bulb Profiles
- Design Ideas & Planting Techniques
- Maintenance, After-Care & Overwintering
- Troubleshooting & Pest Management
- Frequently Asked Questions
1. Understanding South African Climate Zones
To succeed with bulbs you must match species to climate. South Africa spans six horticultural zones (SANBI-style regions) and two broad rainfall patterns.
| Zone | Region Examples | Rainfall Pattern | Summer Bulb Notes |
|---|---|---|---|
| Zone 1 – Coastal Summer Rainfall | Durban, Richards Bay | Hot, humid summers; mild winters | Tropicals thrive (e.g., Tuberose, Canna). Watch fungal disease; ensure airflow. |
| Zone 2 – Coastal Winter Rainfall (Mediterranean) | Cape Town, Stellenbosch | Cool, wet winters; hot, dry summers | Drought-tolerant choices (Eucomis, Gladiolus nanus). Deep mulch and irrigation in summer. |
| Zone 3 – Winter Rainfall Karoo | Calvinia, Clanwilliam | Low rainfall; large temp swings | Indigenous bulbs (Sparaxis) excel; irrigate exotics through heat. |
| Zone 4 – Summer Rainfall Highveld | Johannesburg, Bloemfontein | Summer storms; cold, dry winters with frost | Dahlias, lilies, gladioli excel; lift tender tubers before frost. |
| Zone 5 – Sub-Tropical Highland | Pietermaritzburg, Mbombela | Warm, wet summers; light frost in winter | Zantedeschia (callas) and Crocosmia naturalise easily. |
| Zone 6 – Lowveld & Limpopo | Tzaneen, Phalaborwa | Very hot summers; mild winters | Hippeastrum hybrids and Crinum love heat; give afternoon shade and mulch. |
Rainfall Cheat-Sheet
- Summer-rain zones: Plant once soil warms to ~16 °C (typically mid-September Highveld; late August Lowveld).
- Winter-rain zones: Irrigate summer bulbs through the dry season; plant early September to leverage residual soil moisture.
2. Soil Preparation & Site Selection
Drainage first
Most bulbs hate “wet feet”. If water puddles for 30+ minutes after rain, build raised beds or switch to large containers.
Ideal pH
- Exotics (dahlias, gladioli): pH 6.0–6.5.
- Indigenous Cape bulbs (Ixia, Sparaxis): can tolerate pH ~5.5.
3-Part Bulb Bed Mix (per m²)
- 20 L coarse river sand
- 20 L well-rotted compost
- 2 kg bonemeal or ±60 g organic 3-1-5 fertiliser
Sunlight
- 6+ hours full sun yields the strongest stems and colour.
- Provide afternoon shade for Zone 1 & 6 heat-lovers.
3. Summer Bulb Planting Calendar
Quick-View Table (by Zone)
| Zone | Earliest Safe | Peak Planting | Last Chance |
|---|---|---|---|
| 1 | 15 Aug | 1 Sep – 15 Oct | 30 Nov |
| 2 | 1 Sep | 15 Sep – 30 Oct | 15 Dec |
| 3 | 1 Sep (with irrigation) | 15 Sep – 30 Oct | 15 Dec |
| 4 | After last frost (~10 Sep) | 25 Sep – 10 Nov | 15 Dec |
| 5 | 1 Sep | 15 Sep – 15 Oct | 30 Nov |
| 6 | 15 Aug | 1 Sep – 31 Oct | 15 Dec |
Stagger for success
Plant gladiolus every two weeks from September through November for bouquets into April.
4. Bulb Basics: Bulb vs Corm vs Rhizome
| Storage Organ | Example | Key Planting Note |
|---|---|---|
| True Bulb | Hippeastrum, Crinum | Plant nose at or just below soil surface. |
| Corm | Gladiolus, Ixia | Replace corms every 2–3 years for vigour. |
| Tuber | Dahlia | Eyes up; cover only 3–5 cm. |
| Rhizome | Canna, Zantedeschia | Plant horizontally, ±5 cm deep. |
| Tuberous Root | Tuberose | Soak 4 hours before planting in very dry regions. |
5. Top 20+ Summer-Flowering Bulb Profiles
How to use this section
- Scan the table for your climate match.
- Click the variety/category name to shop.
- Note depth and spacing—bulbs are unforgiving here!
| Bulb | Height | Bloom Months | Best Zones | Depth / Spacing | Water | Pot Friendly | Notes |
|---|---|---|---|---|---|---|---|
| Gladiolus grandiflorus | 1.2 m | Nov–Feb | 1,4,5 | 10 cm / 10 cm | Med | ✓ tall pots | Stake on windy sites; lifts easily. |
| Gladiolus nanus | 60 cm | Oct–Dec | 2,3 | 8 cm / 8 cm | Low | ✓ | Drought-tolerant, smaller flowers. |
| Dahlia (border types) | 45–90 cm | Dec–May | 1,4 | 3–5 cm / 40 cm | High | ✓ | Pinch at 30 cm for more blooms. |
| Oriental Lily ‘Casa Blanca’ | 1 m | Dec–Jan | 4,5 | 15 cm / 20 cm | Med | ✗ deep pot | Intense fragrance; partial shade in Zone 1. |
| Asiatic Lily mix | 80 cm | Oct–Nov | 1–5 | 12 cm / 15 cm | Med | ✓ | Non-scented, fade-proof in heat. |
| Zantedeschia ‘Black Star’ (Calla) | 50 cm | Nov–Jan | 1,2,5 | 8 cm / 20 cm | Med | ✓ | Loves damp soil; semi-shade. |
| Tuberose (Polianthes tuberosa) | 90 cm | Jan–Mar | 1,6 | 5 cm / 20 cm | Med | ✓ tall pot | Evening perfume; great for cutting. |
| Canna ‘Tropicanna’ | 1.2 m | Dec–Apr | 1,6 | 10 cm / 40 cm | High | ✓ large pot | Dramatic foliage; weekly feeding. |
| Hippeastrum hybrid (summer-bloom) | 45 cm | Nov–Dec | 1–4 | Half bulb above soil | Low | ✓ | Keep dry in winter rest. |
| Crocosmia ‘Emily McKenzie’ | 70 cm | Dec–Feb | 4,5 | 8 cm / 15 cm | Med | ✓ | Thrives in Highveld; naturalises. |
| Eucomis comosa (Pineapple Lily) | 60 cm | Jan–Mar | 2,3 | Top at soil level | Low | ✓ | Heat-tolerant; drought-wise once established. |
| Crinum moorei | 1 m | Dec–Feb | 1,6 | Neck at soil level | Med | ✗ | Semi-shade; plant once—lasts decades. |
| Sparaxis mix | 30 cm | Oct–Nov | 2,3 | 5 cm / 5 cm | Low | ✓ shallow | Mass for colour carpets. |
| Ixia viridiflora | 40 cm | Oct–Nov | 2,3 | 5 cm / 5 cm | Low | ✓ | Rare turquoise blooms. |
| Triteleia ‘Queen Fabiola’ | 40 cm | Oct | 2,4 | 5 cm / 5 cm | Low | ✓ | Starry violet umbels; naturalises. |
| Nerine bowdenii | 45 cm | Mar–Apr | 1–5 | Neck above soil | Low | ✓ deep pot | Autumn bonus bloom. |
| Amarine ‘Belladiva’ | 60 cm | Mar–Apr | 1–5 | Neck above soil | Low | ✗ | Hybrid vigour; giant heads. |
| Agapanthus ‘Blue Storm’ | 60 cm | Dec–Mar | 1–6 | Crown at soil | Med | ✓ | Evergreen clumps; drought-wise. |
| Scadoxus puniceus | 40 cm | Nov–Dec | 1,6 | 3 cm / 15 cm | Med | ✓ | SA native with fire-red pompons. |
| Curcuma longa | 80 cm | Feb–Apr | 1,6 | 5 cm / 25 cm | High | ✓ | Edible turmeric rhizomes + orchid-like blooms. |
6. Design Ideas & Planting Techniques
1) “Sunset Layered Pot” (50 cm barrel)
- Back: Cannas
- Mid-layer: Calla ‘Black Star’
- Edge: Trailing Portulaca for spill
2) Highveld Cutting Bed Grid (1 × 3 m)
- Row 1: Gladiolus succession every 2 weeks
- Row 2: Dahlias mixed colours
- Row 3: Oriental lilies for fragrance
3) Mediterranean Gravel Matrix
Combine Eucomis, Crocosmia, Ixia with Lavandula for a drought-proof pollinator strip.
7. Maintenance, After-Care & Overwintering
| Task | Frequency | Notes |
|---|---|---|
| Watering | When top 2 cm dry | Mulch to 5 cm in Zone 2 summers. |
| Feeding | Every 4 weeks with 3-1-5 | High-feeders (dahlias, cannas) respond strongly. |
| Staking | At planting | Prevents root damage later; use bamboo/mesh. |
| Deadheading | Weekly | Extends bloom; channels energy to storage organs. |
| Lifting | Mid-May (Zone 4 frost) | Store gladiolus corms at 10–12 °C, ±50 % RH. |
| Division | Every 3 years | Prevent overcrowding of agapanthus & hippeastrum. |
8. Troubleshooting & Pest Management
| Symptom | Likely Cause | Remedy |
|---|---|---|
| Brown streaks on gladiolus leaves | Thrips | Remove worst spikes; spray neem every 7 days. |
| Yellowing dahlia foliage, green veins | Iron deficiency (high pH) | Drench with iron chelate; lower pH with sulphur. |
| Mushy calla rhizomes | Water-logging | Improve drainage; water less frequently. |
| Bent dahlia stems | Wind damage | Stake early; pinch for sturdier growth. |
Organic hacks: Scatter diatomaceous earth to deter snails; interplant marigolds to help with nematodes.
9. Frequently Asked Questions
How deep should I plant summer bulbs?
Rule of thumb: roughly 3× the bulb’s height measured from the nose down. Examples: gladiolus ±10 cm; calla ±8 cm; dahlia eyes covered 3–5 cm.
Can I plant summer bulbs in the winter-rainfall Cape?
Yes—plant in early September and maintain a weekly soak through the dry summer. Choose drought-tolerant natives where possible.
Do I need to lift bulbs every year?
- Highveld (frost): Lift gladiolus and dahlias after frost blackens foliage.
- Western Cape (no frost): Often left in the ground; cut water May–July for dormancy.
Which bulbs bloom fastest from planting?
- Tuberose can flower in ~90 days.
- Gladiolus nanus can flower ~80 days after planting.
What fertiliser ratio is best?
A balanced 3-1-5 (N-P-K) sustains foliage while supporting flowers and storage-organ development.
