Adding bold swaths of color and elegant, fanned foliage to the late season garden, gladiolus (Gladiolus spp.) are beloved for their showy, ruffled flowers held on upright stems.
The tall spikes of fluttering petals bloom in saturated shades of burgundy, coral, mauve, pink, purple, rose, white, and yellow as well as bicolor combos, adding dramatic appeal to beds, borders, and cutting gardens.
We link to vendors to help you find relevant products. If you buy from one of our links, we may earn a commission.
They can be grown as annuals or perennials, depending on your region, and are generally pretty low maintenance, but if you have problems with your gladiolus not blooming, it’s usually a result of a few common growing mistakes.
In our guide to growing gladiolus, we discuss how to cultivate these flowers in your landscape.
In this article, we’ll unearth the reasons why your gladiolus may fail to bloom and suggest some easy fixes.
As an avid gardener, I was excited to plant gladiolus bulbs in my flower bed last spring. I carefully selected a sunny spot with well-drained soil and planted the bulbs at the proper depth according to the planting directions. However, when summer arrived, I was disappointed to find that my gladiolus plants were not blooming.
After doing some research online and talking to fellow gardeners, I learned that there are several common reasons why gladiolus may fail to bloom In this article, I’ll share the most likely causes and solutions to help get your gladiolus plants flowering.
Improper Storage Over Winter
Gladiolus are not hardy in most zones and need to be dug up each fall and stored indoors over the winter. If the bulbs are not stored properly they can be damaged by cold temperatures and fail to bloom the following season. The ideal storage conditions are cool (40-50°F) and dry.
I store my gladiolus bulbs in breathable mesh bags or paper bags in an unheated basement or garage. Be sure to discard any bulbs that are diseased or rotting, as these can spread problems to healthy bulbs in storage. Inspect stored bulbs periodically and remove any that show signs of mold or mushiness.
With proper overwintering methods, your gladiolus bulbs should keep successfully until spring planting time.
Planting Too Early
Though we all get eager to plant as soon as the ground thaws, gladiolus need warm soil temperatures to thrive. Planting the bulbs too early in cold soil can delay growth and flowering. Wait until daytime temperatures reach at least 65°F before planting.
I try to hold off until mid to late spring for gladiolus planting. You can push the season a bit by warming the soil with black or red plastic mulch. Just make sure no late frosts are predicted that could damage emerging plants.
Inadequate Sun Exposure
Like most flowering bulbs, gladiolus require full sun to bloom properly. “Full sun” means at least 6 hours of direct sunlight daily. Areas that receive morning sun and afternoon shade also work well.
When choosing a planting site, look for spots that are not shaded by trees, shrubs, or buildings. Morning shade is acceptable if afternoon sun exposure is ample. Dappled shade beneath light tree canopies can also work, as long as the sunlight is not too diminished.
Poor Soil Quality
Rich, well-drained soil is key to success with gladiolus. They thrive in fertile loam or sandy loam soils enhanced with compost or other organic matter. Avoid heavy clay soils and areas that collect standing water after rains.
Before planting gladiolus bulbs, work 1-2 inches of compost into the top 6-8 inches of soil to improve drainage and nutrition. I also blend in a balanced bulb fertilizer at this time per package directions. Maintaining optimal soil quality encourages good root growth and flowering.
Insufficient Watering
Like most bulb plants, gladiolus form their flower buds while actively growing foliage. Inconsistent watering during this stage can lead to buds drying up and flowers failing to form.
Gladiolus prefer moist soil while actively growing. Water them thoroughly after planting and provide 1-2 inches of water per week if rainfall is lacking. Use a soaker hose or drip irrigation to target the root zone and avoid wetting foliage excessively.
As flowers begin to bloom, you can reduce watering frequency somewhat. But consistent soil moisture is key, especially prior to bloom.
Pests Like Thrips
Tiny insects called thrips can be a common culprit behind gladiolus plants not flowering properly. These tiny pests feed on leaves and buds, causing deformity, discoloration, and abortion of flowers.
Check plants carefully, especially under leaves, for signs of thrips if your gladiolus are not blooming right. These winged insects are slender and only 1-2 mm long. You may see black dots of excrement on leaves as well.
Control thrips with regular applications of horticultural oil or insecticidal soap. Spray every 7-10 days until you see no further signs of the insects. Be sure to coat the undersides of leaves thoroughly.
Diseased Bulbs
Gladiolus bulbs are susceptible to fungi like fusarium, verticillium wilt, and corm rots. Diseased bulbs often fail to produce any growth above ground or have yellow, stunted foliage.
When purchasing gladiolus bulbs, look for plump, blemish-free ones without signs of mold, lesions, or rotting. Avoid bulbs that are very soft or dried out. Check bulbs carefully in storage as well and discard any that show disease symptoms.
Only plant healthy, disease-free bulbs to avoid problems. Rotate planting sites and allow beds to rest for a few years between gladiolus plantings.
Age Decline
As gladiolus bulbs grow and divide over several seasons, their vigor slowly declines. Older bulbs may produce sparse foliage and fewer or no flowers at all.
Lift and divide bulbs every 2-3 years to maintain productivity. Replant only the largest, healthiest corms. Also amend soil and provide extra fertilization to rejuvenate older beds.
With good care, most gladiolus varieties should bloom well for 5 years or more before declining with age.
Too Much Shade
Gladiolus require full sun – at least 6 hours of direct sunlight per day. Planting in too much shade is one of the most common reasons for no flowers.
Areas that receive only morning sun with afternoon shade can also inhibit good flowering. Choose an open, sunny area clear of trees and taller plants that may shade the gladiolus.
If you must plant in light shade, choose a partially shaded spot that receives at least 4-6 hours of sun daily, preferably in the afternoon.
Excessive Nitrogen
While gladiolus benefit from balanced fertilization, too much nitrogen can promote leafy growth at the expense of flowers. Sources of excessive nitrogen include fresh manure and nitrogen-heavy lawn fertilizers.
Avoid planting gladiolus in close proximity to areas fertilized with high-nitrogen products like manure and lawn fertilizer. Opt for compost and bulb fertilizers that provide a balanced ratio of nutrients instead.
Water Stress
Consistent moisture is important for gladiolus, especially while actively growing foliage and flower buds are forming. Insufficient watering can cause buds to dry up and fail to bloom.
Provide 1-2 inches of water per week from rainfall or irrigation during the growing season. Use soaker hoses or drip irrigation to target the root zone efficiently. Mulching also helps conserve soil moisture.
Corm Age and Size
The size and age of the corm will determine how abundantly it flowers – if it blooms at all.
Corms that have matured – and flowered – for a few years produce new corms that piggyback on top of the old one, eventually replacing the parent which shrivels up and dies.
Along with the new main corm, tiny baby corms, called cormels or cormlets, are produced at the same time, emerging from the seam between the old and new sections.
First year corms are smaller than the parent and typically won’t bloom – they only produce flowers in their second year of growth, and cormlets can take up to three years to bloom.
If you’re dividing an existing clump, make sure you replant only the largest corms – these are the ones that produce the most buds.
First year corms and cormlets can be planted up in pots then placed in an out of the way spot to mature for a year or two before planting out.
When you purchase commercial stock, choose only the largest and healthiest corms for the most abundant blooms.
Corm Planting Depth
With any spring or summer flowering bulbs, one of the most common reasons for seeing plenty of foliage but few flowers comes from planting them too deeply.
Gladiolus corms follow the bulb-planting rule of thumb: plant to a depth that’s about twice the height of the corm.
For large corms, this can be four to six inches deep. Medium sized ones are planted three to four inches deep, and small ones just two to three inches deep.
Gardeners often plant bulbs and corms deeper than is recommended to protect them from winter’s chill.
If you have perennial clumps and worry about damage from freezing temperatures or hard frosts, adding a winter mulch is a better option than burying them too deep.
In mid-autumn, layer on two to four inches of bark mulch, shredded leaves, or straw then remove it in spring.
Your corms will stay safely snug and produce more flowers than when they’re planted too deep.
For a profusion of blooms, gladiolus plants need regular fertilizing and do best with a bloom-boosting feed.
As mentioned, start them out strong by amending the planting site with a shovelful of organic material and mixing in some bone meal when you put them in the ground.
Once the second leaf emerges, feed with a product that has an NPK ratio a bit higher in phosphorus than nitrogen, such as 5-10-10 or 5-10-5. Nitrogen is the first number (N), phosphorus is the second number (P), and potassium is the third (K).
Use slow release pellets scratched into the soil around the plants in early spring and reapply in midsummer.
Alternatively you can use a liquid or water-soluble fertilizer instead, but this should be applied monthly throughout the growing season to promote healthy growth and plenty of blooms.
Another frequent reason for declining flower numbers comes from overcrowding. This is most often an issue with perennial clumps but it can also impact annual plantings.
In the case of perennials, overcrowding happens as the corms mature.
With each growing season, the bulbs increase in size. And at the same time, they’re producing new corms and cormlets – and all are vying for their share of available light, nutrients, and water.
A clump consisting of a dozen or so corms can produce hundreds of tiny cormels and dozens of first year corms, effectively choking out the larger ones and stunting development.
And stunted corms means fewer blooms or flowers that are small and underdeveloped.
To promote vigorous plants with ample flowers, divide your perennial clumps every two or three years in fall. Wait until after blooming is finished, but be sure to do it before hard frosts arrive.
Keep only the mid-sized to large corms for replanting and discard the majority of cormlets – but not in the compost bin, they’ll grow there too!
With annual plantings, overcrowding happens as a result of planting the corms too close together. This can quickly deplete available nutrients which are needed to produce big bulbs for big blooms.
Exhibition plants are grown with a six- or eight-inch spacing, but in the garden, planting corms three to four inches apart is adequate for energetic growth and attractive blooms.
Pest infestations can reduce or prevent flowering as well as contribute to the spread of plant disease. To reduce the risk, always start with top quality corms that have a crisp hull and are free of blemishes, soft spots, and odors.
The most likely culprits to infest your gladiolus plant are aphids, mites, and thrips. If you notice that pests are attacking your glads, apply a natural insecticide like neem oil to get rid of them.
Avoid possible disease issues from botrytis blight, mosaic virus, and rot by controlling pest infestations and planting corms in well-draining soil.
Why Are My Gladiolus Not Blooming?
FAQ
Why do my gladiolus have leaves but no flowers?
Corm Planting Depth
With any spring or summer flowering bulbs, one of the most common reasons for seeing plenty of foliage but few flowers comes from planting them too deeply. Gladiolus corms follow the bulb-planting rule of thumb: plant to a depth that’s about twice the height of the corm.
How can I get my gladiolus to bloom?
Wait a year and fertilize with a balanced 8-8-8 plant food in spring to encourage both foliage and bloom formation. Annual fertilization is key to getting a gladiolus plant to bloom but avoid any food with a high percentage of nitrogen, which helps form foliage.
Why is gladiolus not blooming?
Corm size, fertilization practices and pest problems can prevent flowering. Small, undersized glad corms will produce leaves but no flowers.
When can I expect my gladiolus to bloom?
Gladiolus Soft Innocence, for example, typically blooms in early to late summer, while Gladiolus Circus Color blooms in mid to late summer. Expect to see your flowers to bloom in about 90 days from when the foliage begins to emerge above ground.Jan 29, 2025