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.
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.
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.
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.
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Comments
Traditionally, the corns should be lifted anywhere where temps go below 32 degrees F and the ground freezes solid or you risk loosing them. Lift 3 to 4 days after the first hard killing frost. If you live in a cold climate but enjoyed a warmer-than-average winter, your gladiolus plants may still grow even if they weren't lifted. It does seem that winters are getting warmer as we also live in a cold climate and we've seen some glads that we missed emerging out of the grown.
Hi Andrew,
It takes gladiolus about 90 days from planting until they bloom. If it has already been 90 days since you planted and there are still no blooms, there are a few possible explanations: It could be that there was not enough light (they need full sunlight to bloom), there was too much water (if they are flooded they may begin to rot), or they are too small and young to bloom. For the final possibility, add a little fertilizer mix of 8-8-8 to the soil. If there continue to be no blooms, cut the leaves down in the fall or after they die. Maybe they will bloom next year!
The spot are not likely to be good news, Sheree. Are they brown spots with reddish edges? How is the plant at the soil line? Is it showing any signs of decay? This could be boytrytis blight. It may be that the corm was infected and more serious indications may begin to appear as the season gets on. It is advised not to plant infected corms—but yours are already underway.
If the spots are longish, almost rectangular with brown and yellow, this could be curcularia leaf spot. Again, planting of infected corms is not advised.
There are a number of other problems that can afflict gladiolus corms, also indicated by spots of one color or another. Fungicide is recommended, and not planting infected corms is advised. A nursery person could direct you to the proper fungicide.
There are many reasons why glads don't flower. Here are a few:
• the place they are planted might not be ideal: If there is poor drainage, bulbs can rot; if the area has become shady (such as due to nearby trees or other plants), they are not getting sun; if the soil has become compacted, the bulbs can not push through it (annual lifting and replanting helps to eliminate this problem).
• the bulbs are old: Nothing lasts forever; after a few years, corms just give out.
• the corms have not been fed (fertilized): Annual fertilization helps but do not overdue nitrogen; use a balanced (8-8-8) fertilizer.
• pests and disease: corms are vulnerable to root blights, bacterial scab, and viruses.
It just might be time to replace and replant.
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Gladioli take up to 90 days to bloom, so if you plant them now, they might make it just before the first frost. If you don't mind that your blooms might be a little short-lived, then there's no harm in planting them now. And if they don't end up blooming this year at all, they will at least have had the chance to gather energy for a great bloom next summer!