Overwintering Gladioli: Preparation and Storage

They are sun worshippers and not winter hardy. Therefore, gladioli must be overwintered. Stored indoors, you can prepare the corms for a new flowering season.

Like bells on a stick, the gladiolus flowers rise on upright stems. The gladiolus owes its nickname "sword lily" to its flower shape. The gladiolus presents this impressive picture persistently from June to October. As robust as it may be, it does not survive the winter in the garden. In autumn, the plant retreats into its corm – and you can overwinter that.

The preparation for winter begins as early as October. From now on, watering is stopped so that the corms can store water and thus ripen better. Mid-November is then the time to take the corms out of the ground. You should pay attention to the foliage. Here, gladioli differ from other bulbous flowers. Flower bulbs are usually harvested when the plant's foliage turns yellow. With gladioli, this can already be too late. That's why many gardeners dig up the plants when the foliage is still green. There is agreement that as little green as possible should be cut off. The corm then draws strength from the leaves for a little longer. However, withered foliage is removed. You can either cut it off just above the ground before digging or about 10 centimeters above the corm after digging.

Once you have dug up the plant, the stems are pruned to about 1 to 2 centimeters above the corm. Garden soil should be carefully and thoroughly removed. If the soil is very firm, you can let the corms dry in a warm place for a few days. Then they are easier to clean. In addition, the outer skin of the corm is removed, as well as small offshoots, the so-called cormels. Once you have prepared the corm, let it dry completely for another week as a precaution before moving it to its winter quarters. The corms should also be checked for rot and soft spots. Only store healthy corms. Most corm damage is easily recognizable externally. Discoloration and hardened or soft spots are indications of diseases such as scab, Septoria hard rot, or Fusarium dry rot. Thrips are also a known pest. Removing the corms from the ground early reduces the risk of infestation.

The storage room must be cool, dry, and frost-free. At a temperature of more than 15 °C, the bulbs risk drying out or sprouting too early. A constant temperature of about 5 to 8 °C is better. There are various methods for storing gladiolus corms. The simplest is to wrap them in newspaper and store them in a dry cardboard box. Wooden boxes lined with newspaper are also good winter quarters. No more than three layers should lie on top of each other, otherwise the corms will crush each other. However, it is best if they do not touch at all. If they lie next to each other, the container must be correspondingly large. On a wooden stacking crate, however, the corms can be stacked. Alternatively, storage in a dry mixture of peat and sand is suitable. This can be used to fill gaps so that the bulbs do not bump against each other. In rooms with high humidity, sawdust can be useful. The corms do not need water or fertilizer when they overwinter. However, they should be checked regularly.