How to Grow Gladioli: The Complete Gladiolus Flower Guide

Beautiful multicolor gladiolus flowers in vase.
Photo Credit
Tienuskin/Shutterstock
Botanical Name
Gladiolus spp.
Plant Type
Flower
Sun Exposure
Full Sun
Soil pH
Slightly Acidic to Neutral
Bloom Time
Summer
Flower Color
Multicolor
Orange
Pink
Purple
Red
White
Yellow
Hardiness Zone
8
9
10
11

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Planting, Growing, and Caring for Gladiolus

Catherine Boeckmann

The gladiolus is a classic perennial known for its tall flower spikes and large, colorful blooms! A great cutting flower, the gladiolus looks spectacular in summer bouquets. Come autumn, glads need to be lifted in zones 7 and colder. Learn how to plant, grow, and care for gladiolus in all seasons.

About Gladiolus

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 , “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 zone for the classic Grandiflora gladioli (your typical garden glad) is zone 8 and warmer. Still, it’s well known that by covering the corms with a good mulch, you can keep them alive in zones 6 and 7 for certain varieties such as “Nanus Hybrids.” In colder zones, your glad corms should be lifted, dried, and stored for the winter. 

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Planting

For the best blooms, plant glads in full sun (6 to 8 hours of sunlight per day) in well-drained 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 (13°C). See your local frost dates here.
  • From your last frost date to early summer, plant another round of corms every ten 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 1¼ 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.
  • If planted with other flowers in borders or annual beds, plant the corms in groups of 7 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 them 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 2-3 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.

Learn more tips for storing gladiolus through the winter.

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 are 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,’ which has deep purple-red blooms
  • ‘CԻ⳾,’ for its beautiful, deep pink flowers
  • ‘CDzٲ,’ which sports ruffled flowers in blue-purple
  • ‘Dream’s End,’ which 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,’ which has yellow flowers edged with red
  • ‘Green Time,’ for its unusual lime-green flowers
  • ‘Prins Claus,’ which has white flowers with splashes of pink on its petals
  • ‘P,’ which produces off-white flowers with a yellow center and a pink edge

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 gladiola flowers

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Wit and Wisdom

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

Pests/Diseases

Flowers
About The Author

Catherine Boeckmann

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

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Comments

Please wait and allow the stalks to turn to the color amd consistency of the brown paper bags before removing. If removed to early, it has a tendency to effect the feeding that nature gives to the bulbs/corms during a time we believe is the ugly time. If you are concerned with the appearance, I recommend planted something that may over-shadow that until each is ready for discard. I enjoy the varying degrees of red gladioli and love adding single colors to the bunch to create different effects. Currently, I have Buck-red celosia camoflouging my glads.

Frances Young (not verified)

9 years 2 months ago

This is the first year I put glads in pots on my deck. I noticed that after the flower dies a small seed pod like growth occurs where the flower was. Is this something I can use to grow new ones or is this something that should be discarded?

These are little seed pods. Wait until they turn brown before taking them off the plant. In early spring plant the seeds in pots inside and wait until they are a few inches tall before plating them outdoors. It may take a couple of years before they will flower.

Colorado Glads (not verified)

9 years 2 months ago

I love the gladiola flowers and decided to grow them first time myself. I live in Colorado. Stalks came up and got many stems with buds but they dry up and don't open up or bloom. I have all these stocks and it's a shame the flowers don't open up. Any ideas?

Perhaps you need to put plant food in when you water them, or you need to water them more frequently?

Mani214 (not verified)

9 years 2 months ago

Can you put the corms in the refrigerator over the winter?

They should be fine in a paper bag kept in the vegetable drawer of your fridge. Check them occasionally for rot and throw out any that get mushy.

sawyer45306 (not verified)

9 years 2 months ago

I planted 30 Blue Glads this spring along with 30 white and 30 red. What stumped me was the fact that all 30 blue DIDNT bloom blue at all but bloomed a purplish pink color instead. My question is, could soil ph cause the color difference? If I recall with Hydrangea changing the ph will change color from blue to pink or pink to blue.

There are very few flowers that are a true blue color. Many varieties that are called blue have purple or pink hues mixed in. We don't think that the pH of your soil has anything to do with the color change. There are a few causes for color change, older corms sometimes change color over time and a couple of viruses can also cause color change in glads.

In May of this year (2016), the response to this question indicates that ph level may indeed affect bloom color.