How to Grow Gladiolus
There would be no person in this world who won’t like gladiolus. These tall, elegant flowers with their colorful blooms win the heart of the beholders at once, and one can be easily tempted to grow their very own gladioli. One can plant gladioli to get their flowers cut to make flower arrangements or to adorn their garden along with other plants like celosia, lavatera, and zinnias.
Gladioli are commonly known as ‘glads’ and are native to South Africa. It’s a perennial plant and the best thing about it is that it comes in a range of colors. The plant reaches up to a height of 2 to 6 feet. Flowers too vary greatly in forms and sizes from as tiny as less than 3 inches to as big as larger than 5 inches in diameter.
Published: May 16, 2020.
Gladioli grow best on site with sandy loam soil, ample sunlight, and good water drainage. A gardener who has soil that is good for growing vegetables should rejoice because such soil is great for gladiolus too. Its water drainage and fertility should be increased by mixing compost during spring. The site should be kept free of weeds and other plants because gladiolus cannot compete with other plants.
When to Plant?
Gladiolus can be planted in the spring, right after the danger of frost is over and the temperature of soil has increased to at least 13° C (55° F). From one’s last date of frost to early summer, a round of corms should be planted every 10 days. This will enable the grower to get blooms continuously all through the fall. Flowering will take around 70 to 90 days after planting.
Where to Plant?
Ideally gladioli should be planted in full sun and in well-drained, moderately fertile soil. Heavy, damp soil is not good for glads. If the grower has clay soil, they should grow gladioli in raised beds.
Soil should be prepared by loosening it with a garden fork or tiller to around 12-15 inches deep. Then a 2- or 4-inch layer of compost or aged manure should be mixed in it.
Which Varieties to Choose?
Here are a few gladiolus varieties which are popularly grown by gardeners for their particular characteristics.
Glamini Glads: This is a shorter variety and looks nice when planted in front or middle of flower beds. They are quite pest-hardy and bloom well if they get full sun or even partial shade.
Dream’s End: This variety is up to 3 feet tall. Its light orange flowers with large yellow centers look spectacular. Due to its height, this variety is perfect for back borders.
Black Star: This too is a tall variety, reaching up to 36 to 60 inches of height and its deep purple-red flowers are extremely attractive.
Candyman: This variety has very beautiful deep pink flowers.
Prins Claus: This has an attractive coloration of pink splashes on white flowers.
Gladiolus corms look like crocus corms that are oversized. They are wrapped in a brown fibrous covering and have a small flat bottom. Sometimes spiky shoots are seen at their top.
Large-sized blooms can be achieved when the corms are 1 ¼ inch or even bigger in diameter. Corms smaller than ¾ inch in diameter may not flower during the first year. Also, tall and plump corms should be preferred to wide and flat ones. The bigger the corm, the better will be the flowers.
Corms to be planted should be healthy and not soft or crumbly. Any stored corms that are rotting or damaged should be discarded.
The corms should be planted 4 to 7 inches deep, depending upon their size, and should be covered with 2 inches of soil. The pointed end of the corm should be facing up. When a row or groups of 10-15 corms are planted, the space between them should be 6 to 8 inches. When plants achieve a height of around 6 inches, the soil should be piled up around their base to provide support to the stem.
If the grower wants to harvest flowers, the gladioli should be planted in rows. This makes it easier to take care of the plants and harvest flowers.
If they are to be planted for garden adornment with other flowering plants, the corms should be planted in groups of 7 or more to get the best effect. One can dig an 8-inch deep semi-circular or oval trench for sowing the corns in groups with a 6-inch space between them. The spot should be large enough to handle the number of corns for a nice display.
Space between gladiolus corms while planting should be kept 6 to 8 inches.
Gladiolus plants should be given ample water in order to get the largest flowers. If one’s area receives less than 1 inch of rain per week, gladioli should be watered regularly all through the summer. Otherwise, they should be moderately watered in growth to keep the soil moist.
One can use a rain gauge to check if water should be added. Watering with a drip or trickle system is the best because it delivers water at low pressure at the soil level. If overhead sprinklers are used, it should be used early in the day so that the leaves will get time to dry off before evening so as to reduce disease problems.
When the plants will grow up to 6 to 10 inches in height, a water-soluble fertilizer should be applied 4 to 6 inches away from the stems. The second round should be applied when flower spikes start getting colors.
The soil around the plants should be kept weed-free and a 2-4 inch thick layer of mulch containing wood shavings, bark, or straw should be applied.
Tall varieties of gladiolus need staking so as to prevent the flower spikes from drooping by the wind. As such, the grower can hill the soil around the plant. However, it’s more useful to stake individual flower spikes or form a grid with strings or stakes. This will keep the flower spikes upright. Single stem supports are the best. Dead/faded flowers should be removed to ensure continuous blooms.
If a grower wants to cut gladiolus blooms for bouquets and other ornamentation, they should start cutting the flower spikes on a slant when the flowers that are the lowest on the stalk start showing color.
Stalks having only 1-2 open flowers should be cut; the remaining buds will open later when put in a vase.
Flower stalks should be cut early in the morning or at night, but not during hot times of the day.
When the flower stalk is cut, at least four leaves on the plant should be left to feed the corm for next year’s blooms. Right after cutting, the cut ends of the flower spikes should be immersed in water in a bucket.
Once all the flowers on a stalk are taken away, the stalk should be cut off around 2-3 inches above the soil.
How to Store Gladiolus Flowers?
The bucket with the flowers should be placed in a cool dark place for a few hours before putting them in a vase.
Lower fading flowers should be removed and an inch of the bottom of each flower stalk should be cut off every few days.
How to Store Corms?
Gladioli are completely hardy in USDA plant hardiness zones 8 to 11. In zones 6 and 7, they thrive if the corms are protected by a thick layer of mulch all through the winter.
In zone 5, the corms should be dug up for winter storage before the first frost, except the hardy varieties.
The entire plant should be dug up using a spade. Grasping the top, it should be pulled out of the soil. Corms should not be bruised or injured while digging. All loose soil should be shaken off and damaged cormels should be discarded. The stalk should be cut within an inch above the corm. One can save small cormels separately. If they are replanted each spring, they will bloom in 2-3 years.
The corm should be cleaned off, stalk should be cut within half an inch from the corm, and should be cured in a warm airy location for a week or two. Once dried, the old corm as well as any small cormels should be removed and discarded. The husks on the corms should not be removed. Then the corms should be dusted with a fungicide (bulb dust) to eliminate any diseases.
The new, large corms should be stored in plastic mesh bags in a room which is well-ventilated and has temperatures ranging from 1.6° C (35° F) to 10° C (50° F). These corms should be planted again in spring to get another year full of lovely blooms.
In Zones 6 and 7, the gladiolus beds should be mulched with a layer of straw or hay for winter protection.
Corms can be left in the ground and will sprout back each year. The tops should be cut back and composted in late fall. During cool weather, the corms should be mulched in late November with a 4-6 inch layer of straw or chopped leaves. This will provide winter insulation.
Pests and Diseases
- Gladiolus corm rot (fusarium wilt)
- Gray mold
- Spider mites
- Aster yellows
If stunted, gnarly growth is noticed on a gladiolus plant during the growing season, the plant and the corm should be removed and destroyed, because it may have a virus.
Thrips are the biggest pest on gladiolus. This is a small insect and feeds on leaves and flowers causing typical streaking and discoloring on flowers. They may thrive on stored corms. To avoid this, the stored corms should be treated by dipping them in boiling water for 2 minutes to kill the insect. Then the corm should be dried and then stored. Or the stored corms should be discarded after one year and new corms should be bought.
During the growing season, the plants showing first signs of damage should be sprayed with neem oil or an insecticidal soap to kill the infection.
Can Gladiolus be Grown in Containers?
Growing gladiolus in containers is absolutely possible if one can provide the plant with good growing conditions.
How to Grow Gladiolus in Containers?
To grow glads in containers, one first needs to choose a suitable variety. Shorter varieties are ideal as they are less likely to break unlike the larger ones.
Growers should get a container with drainage holes. Pots without drainage holes should be avoided because then glads will have wet feet and won’t grow well. Corms are also more likely to rot in a wet environment.
The container should be at least 12 inches in diameter and 12 inches deep. It should be deep enough to accommodate the bulb and should be filled with adequate good quality potting soil so that the bulb will be covered. The corm should have at least 2 inches of soil beneath it.
Some gravel should be added to the bottom of the container to ensure good drainage. Waterlogged soil is very bad for gladiolus as its corms will rot in such a soil.
Corms should be planted 2 to 3 inches apart and 3 to 6 inches deep with their flat side down and growing point up. Continuous blooms can be achieved by planting corms at two-week intervals. After planting, corms should be watered generously. The soil should be soaked so that it can settle around the corm.
Caring for Potted Gladiolus
Gladiolus in containers should be regularly watered. It’s better to give a good soaking every week than watering lightly 2-3 times a week. Shortly after the first watering, roots and stems will show.
As mentioned earlier, gladiolus can be cut for making flower arrangements or left on the plant. If they’re left on the plant, dead heads should be cut to ensure continuous growth.
When the plants stop blooming, the foliage shouldn’t be cut down, because leaves keep producing food which is stored in the corm for the next year’s blooming season.
After the blooming season, bulbs should be regularly watered. The leaves will begin turning brown and yellow, and eventually dry down. After this, the container should be emptied. Bulbs should be recovered, soil sticking to them should be allowed to dry, dead foliage should be removed, dry soil should be dusted off and bulbs should be stored in a cool, dry place. Grower can use them for the next year.
By growing gladiolus in one’s own garden or home, one can enjoy a riot of colors that will make their day.