Preparing Gladiolus Bulbs For Winter Storage

Gladiolus bulbs need to be stored indoors because they are not hardy enough to withstand Wisconsin winters in the ground. Gladiolus bulbs are not true bulbs; they are corms (swollen root stems).

Dig up the corms 6 to 8 weeks after bloom or when frost kills foliage. Dig in a circle, allowing ample space around the corms to avoid slicing or damaging them. There might be miniature corms attached to the main one; they are called cormels. Cormels should bloom in two or three years if you save them and replant them each spring. Save the largest ones, at least ½ inch in diameter. Plan to plant them about 1½ to 2 inches deep.

Cut off stems and gently shake off any excess soil. Avoid cleaning with water as it will take longer for the corms to cure (dry). A soft scrub brush can be used to remove soil adhering to the corms. Alternatively, the corms can be cleaned of stubborn soil after curing.

Cure 2 to 3 weeks in a dry, well-ventilated area out of direct sunlight at about 60 – 70 degrees F. Remove old corm and roots from the new corm after curing.

Before storing corms inspect for insects or diseases. Dispose of any damaged or diseased corms.

Store the corms in labeled paper bags in an open cardboard box or layer them in the box with newspaper, packing peanuts, vermiculite, or peat moss. Some sources say the corms should be dusted with a powdered insecticide-fungicide mixture and others omit the insecticide-fungicide. Keeping the corms at a cool temperature (35-40 degrees is ideal) and in a well ventilated area is crucial. DO NOT store the corms in a sealed container or plastic bags and do not allow them to freeze. Periodically check during the storage season and remove any damaged or rotting material.

Barbara Lottmann
Master Gardener

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