How to plant gladioli bulbs – for a brilliant display

Learning how to plant gladioli is an easy way to transform backyard borders into a dazzling summer display. Also known as Sword Lilies, these tall spires of trumpet blooms come in practically every shade from pure white, lime green through to deepest burgundy.

There are also plenty of appealing ruffled, double and bi-colored blooms, perfect for pepping up garden color.

One real bonus of these tall flowering bulbs is that with their upright stems and leaves they take up little room in a border. Providing long-lasting color from summer to fall, try planting bulbs amongst other herbaceous perennials to give garden beds a boost. You can even raise them in plastic nursery pots and pop them into their final position prior to flowering.

'Fall is the perfect time to select your gladioli, before planting in spring. Experiment with new combinations or go for pre-selected bulb mixes for stunning results. 

'Today’s glads are far showier than those that grow in the wild and the color options are simply incredible,' says Diane Blazek, spokesperson for the National Garden Bureau.

Whatever your floral preference, this simple planting guide will tell you all you need to know.

How to plant gladioli

Gladioli are amongst the best summer bulbs. 

‘I love gladioli because they are really just the most impactful flowers to grow,’ says Tabar Gifford from American Meadows. ‘They are stunning, and the impression they make is deceiving for how easy they are to grow. The key for planting is they do need to be planted the full 'depth, or they'll flop over! They also benefit from regular watering if you're not getting rain, which is pretty typical in the peak of summer.’

How to plant gladioli for successional blooms

Flowering from bottom to top, a single gladioli flower spike can provide continuous color for two to three weeks. Perfect for brightening up backyards and vases alike, you can stretch the spectacular display even longer by planting successively.

When to plant gladioli? Begin planting the bulbs outside just before the last frost date – this can vary from late March to early May – depending on where you live. Continue planting batches at fortnightly intervals until early July. This will guarantee an uninterrupted show across the summer right through fall.

How to plant gladioli in a border

Sun loving with a preference for free-draining soil, gladioli are, on the whole, pretty easy to grow. Providing you plant them at the right depth, water and feed them regularly they will reward with masses of long lived and vivid blooms.

Plant to the right depth: Grown from corms (which are very similar to bulbs) gladioli like to be planted around 4-6 inches (10-15cm) deep. ‘High-quality corms may cost more, but larger corms will give you taller stems with more flowers,’ Diane Blazek continues.

For healthy growth aim to water regularly, 1 inch (2.5cm) per week is a good guide and dose with diluted tomato feed fortnightly.

Stake as they grow: With plants reaching up to 39 inches (100cm) these flowers are likely to need staking as they grow, especially if the site is exposed. Use one bamboo cane per stem and slide into position when planting, to avoid accidentally spearing the corm. Secure with soft twine.

Protect indoors over winter: ‘Gladiolus corms are winter hardy in zone 7-10,’ says Kath LaLiberte of Longfield Gardens. ‘In colder areas, you can dig the corms in fall and overwinter them indoors. Alternatively, you can treat your glads as annuals and purchase fresh corms each spring. If you want to overwinter the corms, cut only as much stem as you need, leaving plenty of foliage behind to help the corm replenish its energy for next year.’

If, in milder areas, you are tempted to leave the corms in the ground cover with a thick layer of wood chips or mulch, to ward off any frost and icy chill. There is no guarantee that this will always work but thankfully gladioli corms are pretty inexpensive so can be replaced in spring if necessary.

You can also grow gladioli in pots in a sunny area of your yard, but ensure you provide good drainage.

Should you soak gladiolus bulbs before planting?

If you soak gladiolus bulbs before planting, the corm will be quicker to shoot. Do so overnight to make a significant difference, however note that you will only see shooting a week or so earlier. And, of course, if you're wondering when gladiolus bloom, this will bring it forwards by a week.