How to Grow Gladiolus Corms
Grow Guide #2659
Binomial name: Gladiolus grandiflorus
Life Cycle: Perennial
This 'How to Grow' guide details everything a home gardener needs to know to plant, grow and care for Gladioli (Gladiolus grandiflorus).
When to Plant Gladiolus Corms
Use the table below to identify the best time of year to plant gladiolus corms in your climate.
Gladiolus plants are best grown in full sun. Choose a location that will receive at least 6 hours of full sun each day.
Gladiolus plants produce tall, slender flower spikes that can be damaged in windy areas. Choose a sheltered position away from strong winds.
Gladiolus plants need a loose, well drained soil enriched with organic matter. Prepare soil by weeding it thoroughly, digging it over to at least a spade’s depth to loosen the soil, and adding aged animal manure or compost. Organic matter can be dug into heavy soil to lighten it so roots can grow freely. Keep the area free of weeds until planting. Learn more about preparing soil for planting here.
How to Plant Gladiolus Corms
Gladiolus corms should be planted directly in their final position in the garden.
- Plant individual corms 15cm apart and 10cm deep with the tip pointing upwards.
- Cover with soil and water in well.
- Keep soil moist but not wet until shoots emerge.
How to Grow Gladiolus
Gladiolus plants may need watering during the growing season. Water when the soil is dry about 5cm below the surface (test this by scratching away a little soil with your finger). Water deeply in the early morning or late afternoon. Avoid watering the leaves of plants to avoid fungal diseases. Learn more about watering here.
Gladiolus plants may need to be staked to support them while they grow. If staking, make sure you have the stake in place when you plant corms to avoid disturbing the plant’s roots later. Use a sturdy stake and tie stems gently to the support using twine or plant ties as the plant grows.
Gladiolus plants should flower in approximately 90-120 days.
If growing gladioli for cut flowers, use sharp snips or secateurs to cut the longest stems possible, removing the lower leaves and placing the stems immediately in a clean bucket of water. Learn more about cutting and conditioning homegrown flowers here.
In most climates gladiolus corms can be left for several years to naturalise in the garden. In areas that experience infrequent frosts apply a thick layer of mulch in autumn to protect corms over winter. In areas that experience heavy or frequent frosts corms are best lifted and stored over winter.
To lift corms wait until the foliage turns yellow. Cut the foliage off at ground level, then use a garden fork to lift corms from the soil, taking care not to damage them. Spread the corms on a wire rack in a cool, dry place for 10-14 days to dry them. Then store the corms in a net bag until it is time to replant them.
Common Problems when Growing Gladioli
Like all plants, gladiolus is susceptible to some pests, diseases and other problems. Below is a list of the most common problems gardeners encounter when growing gladiolus plants:
- Aphids are small (2-4mm long) sap-sucking insects that congregate on the new shoots or the undersides of leaves. They can cause leaves to wilt or become discoloured, and also excrete honeydew which can attract ants and other insect pests. To manage aphids, remove them by spraying with a garden hose, apply a soap or alcohol spray, or encourage predatory insects to your garden. Read more about aphids here.
- Rotten corms are caused by pathogens entering corms after sitting in cold, wet soil or being temporarily waterlogged. Corms may show obvious signs of rot or have no roots or shoots. If soaking corms before planting, do not soak them for longer than recommended. Plant corms in free-draining soil, raised garden beds or containers. If growing corms as perennials, lift and store them over winter and replant in spring.
- Thrips are black, beige or white flying insects (<1.5mm) with larvae that suck tissue from leaves and petals, leaving behind very small white or transparent markings. While not usually causing serious damage, the marks affect the look of flowers and foliage and thrips can also transfer pathogens from one plant to another. Wash thrips from affected plants using a garden hose, encourage predatory mites and lacewings with companion planting, or spray with soap, eco-oil or neem oil.
- Slugs and snails are molluscs that feed on tender leaves and shoots, mostly at night, leaving slimy trails behind them. Control them by removing their hiding places, keeping free range poultry, collecting them by torchlight or by placing traps. Read more about slugs and snails here.