How to Grow the Beautiful Gladiolus Flower

By Matt Gibson & Erin Marissa Russell

Gladiolus flowers are very popular both as cut flowers for indoor bouquets and arrangements, and as garden standouts. and Also known as sword lilies, or just glads for short, gladiolus flowers produce some of the most beautiful, awe inspiring blooms you can find for your summer flower garden. There is a gladiolus well-suited to every garden spot you can think of as well, as they are available in a wide range of colors, heights, and flower styles.

The vast array of varieties range in height from two to five feet tall, with bloom sizes that range from miniature blooms, which are less than three inches in diameter, to giant blooms, which span over five inches in width. Flowers are displayed in a totem-like stack on the top portions of their upright stems, hence the nickname, sword lilies. Blooms come in a multitude of colors, including lavender to deep purple, deep maroon to candy apple red, pale to hot pink, soft to bright yellow, white, cream, coral, green, and even multicolor options.

Varieties of Gladiolus Flowers

There are over 260 different varieties of gladiolus to choose from. Having so many cultivars to choose from can be a headache. Luckily, there are certain varieties that stand out from the pack. Here are a few of our recommendations:

Abyssinian Sword Lily – White star shaped blooms with dark-purple centers. Hardy to USDA zones 7 through 10.

Alaska – Beautiful white blooms, can grow up to four feet tall, with 12 flowers on each spike. Attracts pollinators. Hardy to zones 8-11.

Black Star – Deep purple to maroon blooms. A very tall cultivar perfect for back borders. Hardy to USDA zones 3 through 10.

Candy Man – Deep pink flowers. Hardy to USDA zones 8 through 10.

Carine – White trumpet-shaped blooms with purple markings in the center, Hardy to all USDA zones.

Claudia – Grows up to two feet tall with red blooms. Hardy to zones 5 through 10.

Dream’s End – Super tall, good for back borders. Displays light orange flowers with large yellow centers. Hardy to USDA zones 8 through 10.

Glamini Glads – Highly pest resistant, dwarf variety great for front borders. One of the few cultivars to grow well in partial shade. Available in multiple colors. Hardy to zones 3-10.

Greenstar – Dark green foliage contrasts with light green flower petals. Can grow up to four feet tall. Hardy to USDA zones 7 through 10.

Flora – This variety is a five foot monster with deep purple blooms. Hardy to USDA zones 3 through 10. Will grow well in partial shade.

Passos – A garden standout, this cultivar produces stunning purple blooms with red centers and violet edges. Plants grow up to four feet tall. Hardy to USDA zones 3 through 10.

Prins Claus – White flowers with dashes of pink. Hardy to USDA zones 8 through 10.

Yellowstone – Bright yellow midsummer blooms. Hardy to USDA zones 2 through 10.

Honorable Mentions: Applause, Baccara, Blue Moon, Charm, Elvira, Impressive, Nathalie

Growing Conditions for Gladiolus

Plant gladiolus in a location that receives full sunlight. Gladioli will flower in partial shade locations, but the blooms will not be as colorful or vibrant as they would be in full sun, and the plant’s growth could be stunted from inadequate light.

Gladiolus prefers a well-drained, loamy, sandy soil. Gladiolus corms are prone to rotting in heavier, waterlogged soil conditions. If you have a clay-based soil, loosen the beds down a foot deep before planting. Give your gladiolus flowers plenty of space by placing corms six to ten inches apart in your garden beds. Plant small corms two to four inches deep in the soil, and larger corms four to six inches deep.

Sow your gladiolus corms two weeks before the last frost in the spring. For continuous bloomage, stagger the planting and flowering times by planting new corms every two weeks until early July. You can also get the most life out of the flowering season by investing in early, middle, and late season blooming gladiolus cultivars.

How to Plant Gladiolus

Pick a sunny spot with sandy, loamy soil and ample drainage. Amend beds with compost in the spring to improve drainage and nutrient content. Pull up any weeds that pop up in your gladiolus beds regularly, as the flowers don’t enjoy competition. Plant gladiolus corms around two weeks prior to the last spring frost and allow 70 to 90 days for blooms.

Sow corms two to six inches deep into the soil, planting larger corms deeper down and smaller corms less deep into the soil. Cover corms with two inches of soil. Space corms out six to ten inches apart in rows or groups of 10 to 15. When plants become six inches tall, support the stems by hilling up the soil around their bases.

For bigger blooms, plant corms that are at least one and one-fourth inch in diameter (the bigger the better). When planting corms, place them with the pointed end facing upwards. If you are growing your gladioli for cut flowers, plant corms in rows to make them easier to tend and harvest. If planting with other flowers in beds and borders, sow in large groups of 10 to 15, for a more dramatic effect.

Water your corms well just after planting. If you are growing taller gladiolus varieties, Be sure to provide stakes at planting time so that you do not damage the roots driving in stakes when the flowers are mature. Take care to avoid damaging the corms when staking.

Care for Gladiolus Flowers

Fertilize gladiolus with a water-soluble feed when the flowers reach six to ten inches in height, fertilizing four to six inches away from the stems. Feed again when the flower spikes first begin to show color. Weed beds early and often, rooting out any competition on sight. Add a two to four inch layer of organic mulch, like straw, wood shavings, or bark. Provide plenty of water for bigger blooms.

Tall gladiolus cultivars will likely need staking to keep flowers vertical, especially in windy locations. Some support can be given through hilling the soil, but stakes or providing grid support with stakes and string are better than hilling for keeping your gladiolus stalks upright. Single stem stakes are recommended.

Supplement rainfall to keep the soil moist at all times during growth, especially during the summer. Deadhead spent flowers to promote continuous blooming. Once all flowers from a stalk are spent, cut the stalk down to about two or three inches above the soil, but leave some of the plant intact so it will come back the following season.

In zones eight and nine, provide a layer of hay or straw mulch for winter protection. In zones 7 and below, dig up your corms before the first fall freeze and bring them indoors for the winter.

How to Propagate Gladiolus

Gladiolus can be propagated by seed or division. If you want a lot of gladiolus plants and have the time to invest, propagation from seed is the best method. Keep the flowers on the stem for about six weeks after they fade so that the seed casings will fully develop and dry. After six weeks, find the hard casing that houses the seeds. Sprout seeds into small plants for full-sized flowers in approximately three years.

For fewer plants, but quicker propagation, division is the best method. Dig up your corms at the end of summer to store. Each corm will have several cormlets attached to the bottoms. Remove each cormlet and plant them separately. Baby corms planted on their own will develop into full sized flowering plants within two to three years.

Garden Pests and Diseases of Gladiolus

Aphids: Though they come in a range of shapes and shades, all aphids are tiny, and they all tend to congregate on the undersides of leaves. Infested plants will show signs of the aphids sucking moisture from their tissues, such as withered, curled, or deformed leaves. Aphids also secrete a clear, sticky substance that attracts ants. You can stave off aphids with a homemade spray consisting of a liter of warm water, four or five drops of dish soap, and a teaspoon of neem oil. Read more about how to fight aphids in this article.

Aster Yellows: Plants with aster yellows may have stunted growth, exhibit deformed petals that are discolored to green, or develop witch’s brooms from excessive growth. Leafhoppers spread aster yellows, which is similar to a virus. Remove and dispose of any plants showing signs of aster yellows. Clean up the area to take out any weeds nearby, as weeds can be alternate hosts for the leafhoppers that carry the disease. Use diatomaceous earth to manage the leafhoppers that spread aster yellows.

Bacterial Leaf Spot: Bacterial leaf spot first shows up as small clear spots on plants with a wide yellow-tinged edge. These spots gradually spread out and take on an angular or irregular circular shape and develop a red-hued center. Bacterial leaf spot is most common when weather is cool and can cause deformed flower heads. To prevent the disease, water plants from the base instead of allowing foliage to be splashed with water, and do not work around your gladiolus plants when they are wet. Remove and dispose of plants that show signs of bacterial leaf spot, and replace them with plants from an unrelated family so the disease cannot take hold in new plants.

Botrytis Blight: Botrytis is a fungal disease that causes gray mold to appear on gladiolus foliage, buds, stems, and flowers. The disease is exacerbated by cool, wet weather. To prevent botrytis blight, do not water gladiolus at night. Water plants from the base to avoid splashing foliage with moisture. Ensure good air circulation around your plants. Remove and discard any affected portions of plants. Find out more about treating plants with botrytis blight in this article.

Cabbage Looper: Cabbage loopers are green caterpillars with white horizontal stripes that move in a characteristic “looping” motion similar to inchworms. Defend plants with floating row covers to prevent the associated moths from laying eggs on their foliage. If caterpillars appear, pick and squash them or drop them into a bowl of soapy water. Keep the garden cleaned up and avoid accumulation of the plant debris where loopers tend to hide. You can read more about protecting your plants from cabbage loopers in this article.

Slugs: When the weather is wet, slugs come out at night to feed on tender, green parts of your plants, leaving behind holes and mowed down new shoots. You’ll know when a slug has been in your garden by tracing the slimy trails they leave behind. If you catch a slug in the garden, pick and squash it or drop it into a bowl of soapy water. Diatomaceous earth or any brand of coffee grounds sprinkled around vulnerable plants also keep slugs at bay. You can read more about fighting off slugs in this article.

Spider Mites: Spider mites are tiny bugs about the size of a fleck of black pepper, though the color of the inset can be blck or red, brown, or yellow. Like aphids, spider mites suck the juice from plant tissues, but the mites emit toxins that leave white specks on plant foliage. Spider mites also leave behind webbing, and foliage where they have been may turn yellow or become dried out. Spider mites spread most easily when the weather is dry. Because they are so small, simply turning a high-pressure jet of water on your plants is enough to knock them off. Do this every other day, or control using insecticidal soap. You can learn more about treating plants for spider mites in this article.

Thrips: There are many types of juice-sucking thrips insects that can plague the garden, but gladiolus thrips are most common between June and September. Flowers that are prey to thrips will show flecks of white or, in severe cases, turn brown and never open. You can prevent thrips from overwintering on stored gladiolus plants by keeping plants in a frost free spot that doesn’t provide too much warmth to freeze the thrips out. A camphor tablet or bathroom deodorizer placed every so often in your rows of plants will also deter them. Get more details on fighting thrips in this article.

How to Harvest Gladiolus

Gladiolus plants make excellent cut flowers to use in arrangements, but it’s important that you harvest the flowers carefully so they will last as long as possible in the vase. Harvesting cut flowers carefully also means that the plant will remain in good health so it can continue providing flowers for your arrangements for as long as possible.

Flowers should be trimmed for adding to arrangements before or after the heat of the day to avoid unneeded stress for plants. You’ll need a sharp, clean knife as well as a bucket of lukewarm (not cool) water. Choose stalks that are mostly buds, with just one or two open flowers, for the longest-lasting blooms. The other blossoms will open after you cut the stalk and create your arrangement.

Make clean, diagonal cuts through the stem of your desired stalks, then place them into the bucket of lukewarm water. For the plants to continue generating flowering stalks, you should leave at least four leaves behind. Let the flowers rest in a dim, cool spot for a few hours in their bucket of water before you use them in an arrangement. Once the blooms have been added to an arrangement, remove the spent blooms as they appear and trim an inch from the bottom of the stalk every couple of days.

How to Store Gladiolus

Gardeners in cold areas need to dig up the gladiolus plants after they have begun to fade for the fall but before the season’s first frost. Use a clean, sterilized spade and dig the entire plant out of the ground, holding onto the top of the plant to help pull it up.

Be gentle so you do not bruise or damage the corms as you work. If any become damaged, discard them instead of storing them for the winter. Shake the corms to remove excess soil, and trim the stalk to leave just one inch growing from the corm. You can also save the smaller cormels, but keep them separate from the corms, as they should be planted in spring for flowers to appear two or three years later.

Before you store the corms, they should first be allowed to cure (dry out) in the outdoor sunshine for a day or two, unless weather interferes. Remove any excess soil, and lay the corms out on wood trays or flats. Then choose a warm, breezy spot and let the corms cure for two weeks in a spot where the temperature stays between 80 and 85 degrees Fahrenheit (27 to 29 degrees Celsius). The oldest corms at the base of the new ones can then be removed and disposed of.

Leave the husks on the corms you wish to store, and treat them with a fungicide or bulb dust to prevent disease. Add the dust and the corms both to a paper back and shake it well to make sure the treatment gets to all parts of the corms. Then prepare the corms for storage in paper bags, cloth sacks, old onion sacks, or even in pantyhose. Position whichever container you choose with plenty of room between sacks so that air can circulate.

Store your gladiolus corms in a spot where they are safe from freezing and the temperature stays between 35 and 45 degrees Fahrenheit (2 and 7 degrees Celsius). The storage location should also have low humidity. Somewhere like a cool basement will work well. Plant the corms again in the spring to enjoy your gladiolus flowers for another season.

Gardeners have been enjoying the stunning spires of gladiolus flowers in the garden for years. This distinctive flower invokes summer and is an excellent addition to a cut flower garden or holding up the back row of a flower bed as a border flower. With so many different colors and varieties to choose from, there’s sure to be a gladiolus that fits perfectly into your garden this season.