When to Plant Gladioli Bulbs

In the UK, gladioli bulbs — known as corms — should be planted from mid-April to early June. The key factor is soil temperature and frost risk. Gladioli are not frost hardy, so the ground must be reliably frost-free before planting. For a prolonged flowering period, stagger planting every two weeks through late spring. This gives a continuous display from mid-summer into early autumn. Earlier plantings tend to bloom in July, while later ones flower into September.

How to Grow Gladioli

Gladioli thrive in full sun and well-drained soil. They need a position that gets at least six hours of sunlight daily and protection from strong winds, as their tall flower spikes can easily be blown over. Incorporating organic matter into the soil before planting improves drainage and supports better flower development. Gladioli are often grown for cutting gardens but also add vertical interest to borders when planted in groups.

Where to Plant Gladioli

Choose a sunny, sheltered spot with light, fertile soil that drains well. Avoid planting in heavy or poorly draining soils, as this can lead to rotting of the corms. Raised beds or mixed borders work well, particularly if you’re combining gladioli with sturdier, shorter perennials that can help support them. For show-stopping displays, plant in blocks rather than thin rows.

Can You Grow Gladioli from Corms?

Yes — gladioli are grown almost exclusively from corms. These bulb-like structures store energy and regenerate each season. Each planted corm typically produces a single flowering stem, and small new corms form beneath the soil during the season. These can be lifted, stored and replanted for future years, although it may take a couple of years for smaller ones to flower.

How to Plant Gladioli Bulbs

Plant gladioli corms 10–15cm deep, with the flat base facing down and the pointed tip upwards. Space them 10–15cm apart for a dense display, or slightly wider if mixing with other plants. In cooler parts of the UK, planting deeper helps protect them from late cold spells. Water well after planting, and add a layer of mulch to retain moisture and reduce weeds.

How to Care for Gladioli

Water gladioli regularly, especially during dry periods, and feed with a balanced fertiliser every few weeks as they grow. Once buds start forming, switch to a high-potash feed to support blooming. Tall varieties should be staked to prevent wind damage. Remove faded flowers to encourage further blooms and stop the plant focusing on seed production. In autumn, once the leaves yellow and die back, corms can be lifted, dried and stored over winter.

Pests and Diseases

Gladioli are relatively resilient, but thrips can be a problem, especially in hot, dry conditions. These small insects cause silvery streaks on leaves and distorted flowers. Lift and destroy any severely affected plants and avoid replanting in the same spot the following year. Slugs and snails can also target young shoots. Good spacing and airflow help reduce fungal problems like botrytis.

Do Gladioli Come Back Every Year?

In warmer parts of the UK with well-drained soil, gladioli corms may survive winter and return the following year. However, in most areas, it’s safer to lift the corms after the first frost and store them in a cool, dry place over winter. Replant in spring for the best results. With care, the same corms can be reused for several seasons, and new ones will develop alongside the originals.

Are Gladioli Hardy in the UK?

Gladioli are not fully hardy in most of the UK. They can tolerate mild winters in sheltered, well-drained locations, particularly in southern regions. However, wet, cold winters can cause corms to rot in the ground. Lifting and storing them is the most reliable way to protect your investment and ensure healthy plants the next year.

How to Store Gladioli Corms Over Winter

In most parts of the UK, gladioli corms won’t survive winter if left in the ground. Cold, wet soil often leads to rotting, especially in heavy clay or poorly drained beds. Lifting and storing the corms after flowering gives you the best chance of growing strong, healthy plants year after year.

When to Lift Gladioli Corms

Wait until the foliage has turned yellow and started to die back naturally, usually in late October or early November. This means the plant has finished feeding the corm and it’s ready to go dormant. Lifting them too early can lead to weak regrowth in the following season. Don’t wait too long though—corms left in soggy soil for extended periods are more likely to rot.

How to Lift and Clean Gladioli Corms

Use a garden fork to gently loosen the soil and lift the corms without damaging them. Shake off the excess soil and cut back the dead foliage, leaving a short stub. You’ll often see a new corm growing on top of the old one. Gently twist and remove the old, shrivelled base—it’s done its job and can be discarded.

Drying Gladioli Corms

Once cleaned, lay the corms out in a single layer in a dry, airy space out of direct sunlight. A shed, garage, or greenhouse works well. Allow them to dry for about two weeks, which helps toughen the outer skin and prevent mould in storage. Turn them occasionally to help all sides dry evenly.

Storing Gladioli Corms

After drying, store the corms in paper bags, cardboard boxes, or mesh sacks. Keep them somewhere cool, dark, and frost-free—around 5 to 10°C is ideal. Make sure there's airflow to prevent condensation and rot. Don’t store them in plastic bags or sealed containers, as these trap moisture.

Checking During Winter

Inspect stored corms once a month through winter. Discard any that show signs of softness, mould or rot. If you see shrivelling, it may be too warm or dry—move to a cooler, more humid space if possible. Healthy corms will remain firm and dry until spring.