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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>Ron B</span> Tue, 05/13/2014 - 07:53
Can I plant small corms and get flowers
<a title="View user profile." href="/author/editors">The Editors</a> Fri, 05/16/2014 - 17:01

If the corms are tiny plant them in containers to grow bigger. It may take a couple of years before these flower.

 <span>Amanhunt</span> Mon, 05/05/2014 - 23:35
I planted my gladiolus bulbs 12 inches deep before reading it should be about 6 inches. Will it still bloom properly or should I replant them?
<a title="View user profile." href="/author/editors">The Editors</a> Tue, 05/06/2014 - 06:25

If you just planted, we'd re-set the corms 4 inches deep. Otherwise, we've never tried 12 inches so it's an experiment! 

 <span>Sccallen</span> Sun, 07/20/2014 - 19:19
In NY I always plant my glads 12" at a minimum in well draining soil. They grow 6'+ tall on average and need this depth to support the plant in addition to staking support. Additionally, this protects them from the frost / freezing. At this depth I also till the upper 4 to 6" each year by hand to loosen up the soil, carefully though as I have found new bulbs a few inches above the original ones planted. Mine reproduce like rabbits ... or potatoes ... and the average new bulb size is 3 to 4" in diameter. After tending the soil in the spring, I cover with another 2-3" of mulch to keep the weeds down and the soil moist. This works for my area where we have hot and humid summer months.
<span>Shari From Lon…</span> Mon, 07/21/2014 - 23:09
Hi I live in long island Ny South shore I have been very successful with my glads. I never have dug them up but the winters has been getting very cold the past few years and I was wondering if you have been digging up yours? In a bit of a debate if I should.?
<span>Piyubhakta9199…</span> Wed, 04/23/2014 - 13:27
very good and usefully
<span>Diana Kingston</span> Thu, 04/17/2014 - 11:43
I live in Belize, Central America and I have planted Gladiolas for the first time. I planted them three to a pot and set them in my fridge since Belize is so hot all the time. They have sprouted already so how soon can I put them in the ground, and will I have to take them up after they bloom and perhaps store them in the fridge until next year or could I just leave them in the ground all year long?
<span>Demaroge</span> Thu, 04/17/2014 - 12:36
I doubt you need to keep them in the fridge. I live in Georgia and my Gladiolas live outside all year around. It gets very hot and humid here. I would plant them outside in an area where the soil drains well. The corms (that is the seed) stay in the ground here in Georgia over the winter because it doesn't usually freeze. If the ground 'Hard' freezes it will kill them. They don't like to sit it wet soil. They will rot. So, if you have a lot of rain make sure the area you plant them is not heavy clay type soil and that the area doesn't stay 'sopping wet' because it drains well. It gets to be over 100 degrees here and my Gladiolas are in full sun most of the day. I do have to water them sometimes if it hasn't rained. The winter weather here is generally cool with some freezing days (not long enough to freeze through the ground.) I do cover the ground above the Gladiola corms with a heavy layer of mulch after I cut back the leaves yellow. Leave the leaves alone until they yellow because they are storing energy for next year's crop. I hope that helps you. Gladiolas are beautiful! I love to cut the flowers and show them off in a gorgeous vase.
<span>Sk</span> Wed, 04/02/2014 - 09:34
We live in Dallas, TX area and planted the glads for the first time. We seem to be in zone 7B. Do we need to dig up the corms at the end of the season? If so when?