How to grow gladiolus
Overview
Gladiolus is a cormous perennial from the Iridaceae family, grown for its tall, dramatic flower spikes in a range of colours. It requires a distinct warm growing period and full sun to produce its best blooms, making it a seasonal standout in summer gardens.
Varieties
- Gladiolus 'Princess Margaret Rose' — A popular Australian variety with soft pink blooms and a strong, tall stem.
- Gladiolus 'Black Star' — Deep maroon-black flowers, striking in arrangements and a favourite for contrast.
- Gladiolus 'White Prosperity' — Pure white spikes, excellent for cutting and wedding work.
Soil Preparation
Gladiolus prefers slightly acidic to neutral soil (pH 6.0–7.0) with good drainage. Amend heavy clay with sand or organic matter to improve drainage. Add a balanced fertiliser before planting to support strong growth.
Growing Guide
Plant corms 10–15 cm deep and 10–15 cm apart in well-drained, sunny soil. For a succession of blooms, stagger plantings every 2–3 weeks from spring to early summer. Support tall spikes with stakes or netting, especially in exposed positions. Water regularly during active growth but allow soil to dry slightly between waterings to prevent rot.
Care
Feed with a balanced liquid fertiliser every 2 weeks during active growth. After flowering, cut stems to the base but leave foliage to die back naturally. In frost-prone areas, lift and store corms in a cool, dry place over winter.
Companion Planting
Plant gladiolus near dahlias, zinnias, and sunflowers for a vibrant summer display. Avoid planting near beans or peas as they can attract thrips; also keep away from root vegetables that compete for nutrients.
Common Pests & Risks
Thrips cause silvery streaks and distorted flowers; control with insecticidal soap or neem oil. Corm rot (Fusarium) occurs in wet, poorly drained soil; ensure good drainage and avoid overwatering. Aphids may attack new growth; hose off or use pyrethrum.
Harvesting
Cut flower spikes when the lowest 1–2 flowers begin to open, using a sharp knife. Harvest early morning or evening for longest vase life. Remove spent flowers promptly to encourage more blooms on the same spike.
Troubleshooting
Yellow leaves: overwatering or poor drainage; reduce water and improve soil. Brown leaf edges: thrips damage; treat with insecticidal soap. Stunted growth: corm rot from wet soil; lift and discard affected corms. Flowers fail to open: insufficient sun or heat; move to full sun. Spikes lean or break: lack of staking; provide support early.