How to Grow and Care for Gladiolus

Gladiolus (Gladiolus palustris) is a summer bulb, technically called a corm, that can create a garden spectacle of colored blossoms. A member of the Iridaceae family, plants in the genus Gladiolus also go by the name flag flower and sword lily. Fast-growing gladiolus plants are a smart choice for gardens where space is at a premium; they grow to 2-5 feet tall, adding drama to the border. As annuals, the root system is limited, giving it a small footprint for the vertical accent these plants deliver. Even balcony gardens can accommodate a dozen gladiolus corms in a container. 

Move over, cosmos: Gladiolus flowers make excellent vegetable garden companions. The flowers attract pollinating insects to increase those tomato yields, and the bold blossom colors won't get lost between your rows of beans and squash. Plant gladiolus corms in the gaps where you've removed faded spring vegetables like peas and lettuce. 

Gladiolus is mildly toxic to dogs, cats, and livestock.

Gladiolus Care

Here are the main care requirements for growing gladiolus:

• Plant in full sun, however, they tolerate partial shade.
• Use any well-draining soil.
• Water deeply at first, and then weekly after the first watering.
• Plant when the weather is warm, or about 60°F.

Light

Gladiolus do best in full sun, but if it's not available they will still flower in partial shade.

Soil

Any well-draining soil is fine for growing gladiolus bulbs. Although glads can tolerate shallow planting, placing them at least 6 inches under the soil’s surface provides support to emerging shoots.

Water

After the initial planting, water well. Then, water gladiolus weekly.

Temperature and Humidity

Planting glads too early won’t reward you with earlier blooms: Gladioli pout in cold soil, and may even rot. Wait until night temperatures reach 60°F before you set out your gladiolus bulbs, choosing a spot in your garden that receives at least five hours of full sun each day. Gladioli bloom from July until frost. However, the plants don’t bloom continuously, so planting new corms every two weeks will extend the blooming season.

Fertilizer

Fertilize newly emerged gladioli shoots with a balanced, 10-10-10 liquid fertilizer.

Types of Gladiolus

• 'Atom': Red with picotee white border
• 'Boone': Yellow with coral accents; said to be hardy to zone 6
• 'Green Lace': Ruffled chartreuse blooms
• 'Lucky Star': Unusual for its fragrance; white with red throats

Pruning

Pinch back dead flowers after they wither. When the plant is done blooming, cut back the bloom with gardening shears to ground level unless you plan to dig and store your bulbs. 

Propagating Gladiolus

Gladiolus can be propagated by dividing corms. Follow these steps.

1. First, dig up your corms and save them for storage at the end of the growing season. Remove the cormlets (baby corms) from the parent corm, and store them in a dry place until spring.
2. Plant the stored cormlets in a separate area come spring. The plant will not flower in its first year.
3. Dig them up again in the fall and store them over the winter. When spring arrives, plant the corms and expect them to reach flowering size during this second year.
   

Growing Gladiolus From Seed

It is possible to grow gladiolus from seed, however, don't expect to see blooms for many years.

1. Harvest the seeds from gladiolus to propagate via seed.
2. After the flowers have died, leave the blooms on the stalks for about 6 weeks before removing the casing that is filled with seeds.
3. Open the casing, remove the seeds, and store them in a cool dry place until spring (tucking them away in an envelope is good).
4. Sow the seeds indoors in small containers. Add fine sand over the top of the soil and keep the soil moist in a warm, bright location.
5. Seedlings will emerge in several weeks, but allow them to develop leaves before hardening them off.
6. Transplant the seeds to a garden bed when the weather has reached 60°F or warmer. Water regularly as you prepare the plant to flower in the years to come.

Potting and Repotting Gladiolus

Gladiolus grows well in containers. Fill a large, well-draining container with potting soil (you can add compost) and space the corms 3 inches deep and about 4 inches apart. Keep the pot in a sheltered area over the winter, and wait for the plant to bloom again the following year.

Repot the gladioli when the corms begin to crowd each other. Dig up corms, spacing them at 4 inches in the same pot with refreshed soil or in a larger pot to include more corms, Save any extra cormlets for additional pots, for the garden, or to gift to friends.

Overwintering

Gladiolus flowers may perennialize in zone 8 and warmer, but most gardeners treat them as annuals. When the first frost strikes, you can dig your glad bulbs for winter storage. Dry them for a few weeks, and store them in a cool, dry place.

Common Pests & Plant Diseases

Thrips sometimes bother gladiolus plants. You may not see the tiny winged insects, but you’ll notice brown foliage tips and flecked foliage. Treat thrips with insect soap.

How to Get Gladiolus to Bloom

Bloom Months

Gladiolus typically blooms in the summer, between June and July. The blooms will last until the first frost and can come back year after year. You can extend the bloom by planting a succession of corms every few weeks in the spring.

What Do Gladiolus Flowers Look and Smell Like?

Gladiolus's flowers bloom in red, pink, yellow, purple, green, orange, and white. Gladiolus plants produce trumpet-shaped flowers that open from bottom to top on a sword-like stem, adding drama to the landscape and bouquets alike. Hybridizers have expanded the color palette so that few flowers rival it, short of bearded irises. One color you won't find in the glad flowerbed is true blue.

Some people describe the scent as warm, evoking notes of clove and almond, while others say it smells sweet like carnation or honeysuckle.

How to Encourage More Blooms

To encourage more blooms, regularly fertilize gladiolus with an 8-8-8 balanced fertilizer mixture that is not high in nitrogen. This will help form foliage, which will bring more blooms.