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How to Grow Gladiolus: Planting, Caring for, and Storing Gladioli Corms

Beautiful multicolor gladiolus flowers in vase.
Image Credit:
Tienuskin/Shutterstock
Botanical Name
Gladiolus spp.
Grown as
Tender Perennial
USDA Zones
8a
8b
9a
9b
10a
10b
11a
11b
Toxicity
Toxic
Sun Exposure
Full Sun
Water Needs
Moderate
Height
3-6 feet
Spread
1–3 feet
Soil pH
Neutral
Bloom Time
Summer
Flower Color
Multicolor
Orange
Pink
Purple
Red
White
Yellow
Special Features
Container-Friendly
Cut Flower
Attracts Butterflies
Attracts Hummingbirds
Attracts Pollinators
Deer-resistant
Rabbit-resistant
Resilience
Heat-Tolerant
Plant Type
Bulbs
Written By: Catherine Boeckmann Executive Digital Editor and Master Gardener

Gladiolus—tall, dramatic, and bursting with color—is the showstopper of any summer garden. Whether you call them glads or garden gladiators, these bold bloomers add height and flair to beds and bouquets alike. But when autumn creeps in, it’s time to lift those corms or tuck them in with mulch. 

Ready to grow your own floral fireworks? Here’s how to plant, care for, and store gladiolus like a pro—zone by zone.

Part of the iris family (Iridaceae) and commonly known as “glads,” these lovely flowering plants are available in a multitude of colors and sizes—from the smaller hybrids that fit perfectly in containers to the large-flowered Grandiflora hybrids, which send out huge spikes of blooms in a range of colors. 

The most common gladioli typically reach between 2 and 5 feet in height, sporting flowers ranging in size—from “miniature” blooms less than 3 inches in diameter to “giant” flowers greater than 5 inches across! The taller varieties, which need to be staked, are often placed in the back of a garden to complement shorter plants nicely.

“The gladiolus ‘bulb’ is actually a food-storage structure known as a corm,” explains David Trinklein, a Horticulture Extension State Specialist at the University of Missouri, “Botanically, corms are flat, thickened underground stems. Gladioli growing natively in South Africa were exposed to a dry season. It was the function of the corm to maintain the plant while dormant until growth resumed after the spring rains began.”

Gladiolus Winter Hardiness

The accepted hardiness zones for the classic gladioli in the Grandiflora group (your typical garden glads) are Zones 7 or 8 and warmer. Still, it’s well known that by covering the corms with a good mulch, you can keep gladioli alive in Zones 6 and 7, or in even colder zones for certain varieties such as Nanus hybrids. In colder zones, your glad corms should be lifted, dried, and stored for the winter. 

 Find your USDA Plant Hardiness Zone here.

Planting

For the best blooms, plant glads in full sun (6 to 8 hours of sunlight per day) in well-draining soil that’s moderately fertile. They will not do well in heavy, soggy soil. Mix compost (humus) into your soil to improve consistency and fertility.

When to Plant Gladiolus

  • Start planting gladiolus corms in the spring once the danger of frost has passed and the soil has warmed to at least 55°F (about 13°C). See your local frost dates here.
  • From your last frost date to early summer, plant another round of corms every 10 days or so. This will result in continuous blooms through early fall!
  • Depending on the variety, it takes between 60 and 90 days from the time glads are planted for the corms to root, grow, and bloom.
Gladiolus corms in a metal bowl
Gladiolus corms

How to Plant Gladiolus

  • Ready your garden by using a garden fork or tiller to loosen the soil to about 12 to 15 inches deep. After loosening the soil, mix in a 2- to 4-inch layer of compost or aged manure.
  • To ensure large-sized blooms, plant corms that are 1-1/4 inch or larger in diameter.
  • Set the corm in the hole about 4 inches deep with the pointed end facing up. Cover with soil and press firmly.
  • Space the corms 6 to 8 inches apart.
  • If you grow gladioli primarily for cut flowers, plant them in rows. It’s easier to tend the plants and to harvest the flowers this way.
  • If you plant glads with other flowers in borders or annual beds, plant the corms in groups of seven or more for the best effect.
  • Water the corms thoroughly at planting.
  • If you’re planting tall varieties, be sure to stake them at planting time. Be careful not to damage the corms with the stakes.

Growing

How to Grow Gladiolus

  • Put a 2- to 4-inch layer of mulch around your gladioli to keep your soil moist and help prevent weeds.
  • If you get less than 1 inch of rain a week, water your plants regularly throughout the summer. Otherwise, water them moderately when they are growing to keep the soil moist.
  • Remove the faded/dead flowers to ensure continuous blooms. Once all the flowers on a stalk are gone, cut the stalk off at about 2 to 3 inches above the soil.
  • Be sure to leave the plant intact so it can mature and grow the corms for the next season.

Winter Protection for Gladiolus

  • If you live in USDA Hardiness Zone 8 or warmer, put down a layer of hay or straw for winter protection. Gladiolus can remain in the ground through winter, provided a hard freeze (28°F or colder) isn’t common in your area.
  • In colder regions (Zone 7 or colder), dig up gladioli corms once the foliage has faded after the first fall frost. A light frost will kill the foliage but not the rest of the plant. Be sure to dig up the gladiolus corms before a hard freeze (28°F), or the plants could be fatally damaged.
  • All that said, many gardeners who live in the “border” Zones 6 and 7 have tried leaving glads in the ground and found that they survived; this is a judgment call based on your microclimate, your variety of gladiolus, and climate shifts.

purple and red Gladiolus flowers

Digging Up and Storing Gladioli Corms

To dig up the gladioli corms for winter storage, follow these tips:

  • Use a spade and dig up the entire plant, grasping the top to pull it out of the soil. Avoid bruising or injuring corms while digging. Shake off all loose soil (do not wash them off) and discard damaged corms. Cut the stalk down to 1 to 2 inches above the corm. Save the small cormels separately if you so desire. These will bloom in 2 to 3 years if you replant them each spring.
  • Allow the corms to dry in the sun for 1 or 2 days if the weather agrees. Sift out excess soil and place corms in wooden flats or trays. Cure in a warm and airy location for 2 to 3 weeks. Remove and throw away the oldest bottom corms (from the base of the new ones).
  • Don’t remove the husks on the corms.
  • Dust the corms with a fungicide (“bulb dust”) to avoid disease problems. Place dust and bulbs in a paper bag and shake vigorously.
  • Store the corms in paper or cloth bags, pantyhose, or old onion sacks. Stack or hang the containers, so air can move among them. Store the corms at 35° to 45°F (2° to 7°C) in low humidity. A cool basement is quite suitable. Do not allow corms to freeze.
  • Replant these corms in the spring for another year of beautiful blooms.

Harvesting

To cut glads for bouquets, follow these tips:

  • Cut the flower stalks early in the morning or at night, not during the heat of the day.
  • Use a sharp knife and bring a bucket of lukewarm water to the flower bed; cut diagonally through the stalks and place in the bucket.
  • Cut stalks with only one or two open flowers. The rest of the buds will open after you put them in a vase. Leave at least four leaves on the plant in the ground if you want to reuse the corms.
  • Place the bucket with the flowers in a cool dark place for a few hours before arranging them in a vase.
  • Remove lower fading flowers and cut about 1 inch off the bottom of each flower stalk every few days.

Purple gladiolus flowers

Pests and Problems

Types

Gladioli come in a variety of sizes and colors, with the most popular being part of the following hybrid groups:

  • Grandiflora Hybrids: These are the classic gladioli that produce a plentiful amount of large (5- to 6-inch) blooms in a range of colors. The plants produce flower stalks that reach up to 4 feet in height and can be winter hardy to Zone 7.
  • Dwarf Grandiflora Hybrids: These miniature glads are an excellent choice for containers and cutting gardens, as their flowers are about half the size of Grandifloras, and their shorter stalks don’t typically require staking. They are also winter hardy to Zone 7. Glamini gladioli are included in this group; they are pest-resistant and will bloom in full sun or partial shade.
  • Nanus Hybrids: Hardy to Zone 5, these smaller gladioli look a lot like Grandifloras, but do not produce as many flowers. They tend to grow no larger than about 2 feet in height, which makes them perfect for containers or small spaces.

Some specific gladiolus varieties of note include:

  • ‘Black Star’ has deep purple-red blooms.
  • ‘Candyman’ is known for its beautiful, deep pink flowers.
  • ‘Costa’ sports ruffled flowers in blue-purple.
  • ‘Dream’s End’ makes a good background plant because its flower spike is up to 3 feet tall (and it has pretty light orange flowers with large yellow centers).
  • ‘Fun Time’ has yellow flowers edged with red.
  • ‘Green Time’ is grown for its unusual lime-green flowers.
  • ‘Prins Claus’ has white flowers with splashes of pink on its petals.
  • ‘Priscilla’ produces off-white flowers with a yellow center and a pink edge.

Wit and Wisdom

  • Gladiolus is one of the August birth flowers.
  • Gladioli are sometimes called “sword lilies” due to their blade-like leaves. “Gladiolus” comes from the Latin gladius, meaning “sword.”
  • In the language of flowers, gladiolus signifies remembrance. Learn more flower meanings!

Bulbs

About The Author

Catherine Boeckmann

Catherine Boeckmann

Executive Digital Editor and Master Gardener

Catherine Boeckmann loves nature, stargazing, and gardening, so it’s not surprising that she and The Old Farmer’s Almanac found each other. She leads digital content for the Almanac website and is also a certified master gardener in the state of Indiana.

Read more from Catherine Boeckmann

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Comments

<span>Anonymous</span> Sat, 04/06/2013 - 15:40
I live in RI, if I put hay on the top of my flower beds in the fall will the bulbs be ok for the winter
<span>Anonymous</span> Mon, 04/22/2013 - 12:05
Where I live, I have never had to dig up my bulbs,(gladilous,tulips,cana,daffodils,columbine, etc;). All I do is put the Fall leaves on my flower beds before the 1st frost. Hope this helps you. Happy Gardening!
<a title="View user profile." href="/author/editors">The Editors</a> Mon, 04/08/2013 - 20:02
Most of RI is too cold to cover with hay. In hardiness zones 7 or colder, corms should be dug before the first frost, stored, and replanted in spring.
<span>Anonymous</span> Mon, 04/22/2013 - 12:15
I have way to many Glads in my flower beds. They have started to come up and have the green stems on them, can I transplant them now before the flowers open up to other areas in my yard?
<a title="View user profile." href="/author/editors">The Editors</a> Mon, 04/22/2013 - 12:42
Yes, you can transplant them now. Dig carefully so that you don't disturb the bulbs and roots. Plant in new spot and keep watering to prevent transplant shock. You may loose a few flowers but most should be just fine.
<span>Anonymous</span> Thu, 03/28/2013 - 12:35
I live in Oklahoma and am planting a few gladiolus as well as a few other things for the first time this season, and I am not quite sure when exactly I should plant them? I know they say last frost, but that's sometimes hard to determine here.
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 04/16/2013 - 10:12
You can plant the glads now. See our frost chart at almanac.com/content/frost-chart-united-states with last spring frost dates shown for Oklahoma.
<span>Anonymous</span> Mon, 03/18/2013 - 10:55
I bought corms last November and I would like to plant them this coming April. Thing is is that they were on clearance from last summer - would it be okay to plant them after they've never been in soil for this long? How long can the corms last without being planted? I kept them cool & dry all winter. Thanks!
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 03/19/2013 - 10:42
As long as the corms are dry and there is no visible rot they are fine.
<span>Anonymous</span> Sun, 03/17/2013 - 20:17
So Im planting gladiolus this spring :) been wanting to for awhile. Just wondering if I should lift the bulbs in winter? I live in paso robles, California, zone 8 :)