Caring For Gladiola
The care information provided in this section represents the kind of practical advice is available for all the plants in this web site if you subscribe to the monthly customized newsletter Yardener’s Advisor.
Given the basics, decent soil, some fertilizer, sufficient water and sun, glads need very little attention. Mulch will discourage weeds. Their tall flower stalks will need staking, however. If they are in rows, simply stretch a string along the row on both sides of the plants and stake it at each end. For individual plants, drive a stake into the soil nearby, being careful not to harm the corm, and loosely tie the glad flower stalk to it with string or cloth strips. Cut off flowers that have bloomed and died. Allow the glad leaves to yellow and die back for about 6 weeks after the flowers are finished. After this, corms may be dug up to winter over inside.
Ideally, glads should get 1 inch of water a week. It it doesn't rain dependably, check the soil under the mulch to see if supplemental watering is necessary. During hot, dry weather, water thoroughly once a week.
A crucial time for water is when the flower spike emerges from its sheath. Although gladioli don't need much water while they're flowering, regular moisture is necessary later to encourage rooting and help the corm store up nutrients for next season. For information on products see the file on Choosing Watering Equipment
Feed bulbs when they are planted. Mix about 1 tablespoon of all-purpose granular fertilizer or commercial bulb food per corm into the soil where the corms are to be set. After planting each corm, fill its hole with this enriched soil. Rainwater will carry the nutrients down to the roots as it soaks in. Serious gardeners sometimes sprinkle a little more granular fertilizer on the soil around the bulb bed later in the growing season or spray the glads with liquid fertilizer when they have developed 5 leaves to give them a boost. Don't feed glads immediately after they flower when the corms can least use the nutrients--that just encourages disease.
Mulching and Weed Control
A 1 or 2 inch layer of an attractive organic material such as chopped leaves, bark nuggets, or wood chips spread on the soil around the glads helps control weeds, conserves soil moisture, and keeps dirt from splashing up on the flowers. More than 2 inches will force the emerging glad stems to travel too far to reach the light as spring progresses. For more information see the file on Using Mulch
Cut flowering glad stems for indoor display in the early morning. Choose stems where the lowest flowers are just opening. Use a clean, sharp knife. Leave at least 5 leaves behind on the corm to allow it to continue developing. Plunge flower stalks into a pail of warm water for several hours or even overnight. Arrange them in a container after adding a teaspoon of sugar per quart to the water to prolong their freshness. Harvested when the lowest bud on the spike is just starting to open, their bloom display lasts up to 10 days. For more information see the files on Keeping Cut Flowers and Cut Flower Supplies
In the south, corms can be left in the ground for several years before they must be dug up. In the North, they must be removed from their beds every year. About 6 weeks after they bloom, about the time the leaves begin to turn yellow, carefully dig up the corms. Gently shake the soil off of them. Cut off the dying stems just above the top of the corms, and burn or discard them to destroy any pests that may be present. Allow the corms to dry out on a ventilated tray or flat, then treat them with bulb dust to destroy any residual thrip eggs.
Keep them in a dry, dark, ventilated place where the temperature is steady at 60° to 70°F. Store corms in single layers in flats or ventilated trays (if they are stacked, place blocks between them to permit air circulation). Corms can also be stored in paper bags; in shallow boxes covered with dry sand, soil, shavings, or vermiculite; in open-mesh bags; or in paper cartons. When the corms are properly cured (in about 3 weeks) you can easily pull off the old withered corm and roots from the new plump corm on top.
Glads reproduce themselves and give you more plants. When they are dug up for the winter, glad corms will have small "cormels" about the size of peas attached to them. These may be stored along with the new corms and planted out at the same time next season. Soak cormels in water for 2 days before planting, to help them sprout faster. Cormels produce flowering plants in 2 to 3 years.
Another way to increase your gladioli plants is by dividing their corms. Cut large, sprouted corms in half, right between 2 sprouts. Each half will then produce a new plant.