Gladioli (singular: Gladiolus), often affectionately called "glads," are strikingly beautiful flowering plants prized for their tall, sword-like foliage and vibrant, showy blooms. Belonging to the iris family (Iridaceae), they grow from corms — swollen underground storage organs — and produce impressive flower spikes typically reaching 60–120 cm (2–4 ft) in height.

Each spike can carry up to 20 individual funnel-shaped flowers that open sequentially from the bottom upwards, creating a cascading, long-lasting display. Gladioli are available in an extraordinary range of colours including red, pink, white, yellow, orange, purple, lavender, and multicoloured varieties, making them extraordinarily versatile in the garden and as cut flowers.

Gladioli prefer well-drained soil and full sun, thriving in warm summer conditions. They are planted from corms in spring once soil has warmed sufficiently, and reward gardeners with dramatic blooms in mid to late summer. In colder climates, the corms must be lifted and stored over winter to prevent frost damage.

In the language of flowers, gladioli symbolise strength of character, integrity, and remembrance, making them a meaningful choice for both celebratory and memorial occasions. Their elegant form and wide colour palette ensure they remain a favourite in borders, cutting gardens, and floral arrangements worldwide.

How To Grow

Growing Gladioli

Gladioli are grown from corms (swollen underground storage organs) and are straightforward to cultivate given the right conditions.

Soil Preparation

Choose a site with well-drained soil and full sun (minimum 6–8 hours per day). Loosen the soil to a depth of 30 cm (12 inches) and incorporate generous amounts of compost or well-rotted organic matter. Gladioli prefer a slightly acidic to neutral soil pH of 6.0–7.0. On heavy clay soils, add grit or coarse sand to improve drainage, as waterlogged conditions will cause corms to rot.

Planting Corms

Plant corms in spring once the soil temperature has reached at least 13°C (55°F) and the risk of hard frost has passed. For a succession of blooms throughout the season, plant corms every two weeks from early spring through to early summer.

• Depth: Plant corms 10–15 cm (4–6 inches) deep, pointed side up
• Spacing: Space corms 15–20 cm (6–8 inches) apart in rows
• Water well after planting

Watering

Keep the soil consistently moist throughout the growing season, aiming for the equivalent of approximately 2.5 cm (1 inch) of water per week. Water at the base of plants rather than overhead to reduce the risk of fungal diseases. Reduce watering as the foliage begins to die back at the end of the season.

Feeding

Apply a balanced slow-release fertiliser at planting. As flower spikes develop, switch to a high-potassium feed to encourage strong stems and vibrant blooms. Avoid excessive nitrogen, which promotes leafy growth at the expense of flowers.

Staking

Gladioli produce tall, top-heavy flower spikes that are vulnerable to wind damage. Insert sturdy stakes or use a plant support ring when plants reach approximately 30 cm (12 inches) in height. Tie stems loosely to avoid bruising.

Mulching

Apply a 5–8 cm (2–3 inch) layer of organic mulch (straw, bark chips, or compost) around the base of plants to conserve soil moisture, suppress weeds, and moderate soil temperature.

Winter Care & Corm Storage

In climates where winter temperatures regularly drop below -2°C (28°F), corms should be lifted after the first autumn frosts cause the foliage to yellow:

1. Cut stems to approximately 5 cm (2 inches) above the corm
2. Carefully lift corms with a fork, shaking off excess soil
3. Allow corms to dry in a warm, airy location for several days
4. Remove shrivelled old corms and trim any remaining stems
5. Store healthy corms in paper or mesh bags in a cool, frost-free, well-ventilated space at 4–10°C (40–50°F)
6. Replant the following spring

Harvesting

Harvesting Gladioli as Cut Flowers

Gladioli make exceptional cut flowers and harvesting them correctly ensures the longest possible vase life and an impressive display.

When to Cut

Harvest gladioli when the lowest two or three flowers on the spike have just begun to open, with the remaining buds still closed. These buds will continue to open sequentially over the following days, extending the display. The ideal time of day to cut is early morning or late evening, when temperatures are cooler and stems are fully hydrated.

How to Cut

• Use a clean, sharp knife or pruners — blunt tools crush the stem and reduce vase life
• Cut at a 45-degree angle to maximise the surface area for water uptake
• Always leave at least 4–5 healthy leaves on the plant after cutting; these are essential for photosynthesis and allow the corm to continue building energy reserves for the following season
• Immediately plunge cut stems into a bucket of clean, cool water

Conditioning for the Vase

• Allow cut stems to stand in water in a cool, shaded location for 2–3 hours before arranging
• Add a commercial floral preservative to the water, or use a homemade solution of 1 teaspoon of sugar and a few drops of household bleach per litre of water
• Use a tall vase to support the long stems and prevent them from bending
• Remove any leaves that would sit below the waterline to prevent bacterial growth

Maintaining the Arrangement

• Change the water every two days, re-cutting the stem ends each time
• Keep the arrangement away from direct sunlight, heat sources, and draughts
• Remove individual spent flowers by pinching them off as they fade; the remaining buds will continue to open

After Harvest

Allow remaining foliage on garden plants to continue growing after cutting. Do not remove or cut back the leaves until they have naturally yellowed and died back, as this period is critical for corm development and energy storage for the next season.

Common Problems

Common Problems with Gladioli

Thrips (Thrips simplex)

Gladioli thrips are one of the most common and damaging pests. They feed on foliage and flowers, causing silvery streaking, distorted growth, and discoloured blooms. Infestations are worst during hot, dry weather.

Control: Remove and destroy heavily infested plant material. Inspect corms before storage and discard any that show signs of thrip damage. Dusting stored corms with an appropriate insecticide powder can reduce carry-over to the following season.

Fusarium Corm Rot (Fusarium oxysporum)

A serious fungal disease causing corms to develop dark, sunken lesions and rot. Infected plants may wilt, yellow, and die prematurely. The disease persists in the soil for many years.

Control: Rotate planting sites, avoid waterlogged conditions, and only plant healthy, firm corms. Remove and destroy infected plant material immediately. Do not compost diseased material.

Botrytis (Grey Mould)

Grey mould (Botrytis gladiolorum) causes water-soaked spots on leaves and flowers, which develop a fuzzy grey coating in humid conditions.

Control: Ensure good air circulation around plants, avoid overhead watering, and remove infected material promptly. Fungicide treatments may help in severe cases.

Dry Rot (Stromatinia gladioli)

Small, dark lesions appear on the corm, which eventually shrinks and mummifies. Infected plants produce stunted, yellowing growth.

Control: Only plant firm, healthy corms. Improve soil drainage and rotate planting sites regularly.

Aster Yellows

A phytoplasma disease transmitted by leafhoppers causing yellowing, stunted growth, and deformed flowers.

Control: Control leafhopper populations and remove infected plants immediately. There is no cure once a plant is infected.

Neck Rot & Penicillium Storage Rot

Blue-green mould developing on corms during storage, caused by Penicillium species.

Control: Ensure corms are thoroughly dried before storage, maintain good ventilation in the storage area, and discard any soft or mouldy corms before replanting.