Methods of curing gladiolus corms have been modified in recent years to reduce winter injury from disease and thrips to a minimum.
Quick drying, even by the use of heat, is extensively used by both commercial and amateur growers.
However, to have sound, clean corms for planting next spring, one should follow all the latest, approved steps for digging, curing, and storing.
Digging Gladiolus Corms
Gladiolus corms are mature enough to be dug four weeks after the bloom is over. When the weather in late September and early October is warm and wet, the plants will continue to grow, increasing the size of both the corms and cormels.
Most gardeners wait until their plants have reached their optimum growth, or they dig just before the first killing frost is expected.
A light frost does not hurt the leaves but a killing frost will. Therefore, when the leaves show frost injury, dig the corms at once, or they may not remain healthy.
When the gladiolus crop is large or when drying space indoors is limited or unavailable, the corms must be dug earlier because it takes longer to cure them outdoors than it does indoors.
Soil
Choose a warm, sunny day when the soil is dry for digging. The soil will then fall away easily from the corms.
Gardeners who save the cormels, particularly of expensive new varieties, will find that the cormels remain attached better when the soil is dry.
Lifting plants out is loosening the soil thoroughly under and around them with a spading fork or pointed shovel. Unless the soil is heavy clay or wet, plants may be lifted carefully from the soil by the foliage.
By digging a row at a time and keeping all labels in position, the job can be done quickly and without mixing the varieties.
Cut the tops off cleanly and close to the corms with sharp pruning shears. Later, when the tops are dry, burn them to destroy thrips and diseases.
Curing Corms
Corms can be cured in several ways. The object is to remove excess moisture in the corms quickly, prepare them to remove the old corm and roots at the base and harden them for winter storage.
Where warm weather permits, corms can be cured in wooden trays, or flats left out in the field or garden, corms should not be placed more than three inches deep in a container.
The flats are piled in a pyramid fashion, with dividers between each layer to let air circulate freely around them.
Always have a cover, such as canvas, to throw them over on frosty nights or rainy weather. Also, keep the topmost flats covered so the sun will not harm corms.
The length of time required to cure or dry corms varies with the amount of heat and ventilation, the degree of maturity of plants, and the inherent traits of the variety.
The best methods require about two weeks. Gardeners should allow from two to four weeks to do the job right. After two weeks of curing in dry weather outdoors, check the corms. If the old corms come off easily, they’re ready to be cleaned and stored away. If not, they need more time to dry.
Both the garage and shed make ideal drying places if they are well-ventilated and can be closed in bad weather. However, corms may be frozen if the temperature drops below 32° degrees Fahrenheit. Late in the season, therefore, check the temperature on cold nights.
Drying With Heat
Most large commercial growers have hot air drying systems that cure corms rapidly and economically.
Amateurs can improvise their heating systems which will work well if ventilation is good. Otherwise, the curing room will be dripping wet.
The gardener with only a few trays of corms to dry can place them on top of the oil burner in the cellar, over a hot air furnace register, or on a rack near the basement ceiling if it is warm and dry enough.
The hobbyist who grows 100 varieties and has a lot of trays to contend with needs a heater and a ventilating fan to do a good job of quickly curing indoors.
Usually, this is not economical except for commercial growers. Therefore, amateurs are better off using one of the drying methods described earlier.
One should not hurry the drying process by using excessive heat. Too high temperatures will cause the corms to shrink, become hard, or die. A maximum temperature of 90° degrees with an average of 85° degrees Fahrenheit is ideal.
When the old corn can be easily pulled from the new corn, the batch is ready to be cleaned. However, when the old corn comes off easily lasts only a few weeks, and the job should be done then.
Later, one must use a knife to pry off the old corm. This results in bruises and cuts on the new corm, which opens the way to infection by disease.
If you save the cormels for propagation, pick them out at cleaning time and store them in paper bags with their respective varieties.
Cleaned corms need another week of curing in a 70- to 80-degree room to form a heavy layer of tissue over the scar where the old corn was removed.
Before Storing
Dust the corms liberally with 5 percent DDT, 5 percent DDT, and 7 percent metallic copper, or 5 percent DDT and Fermate, or soak in Ortho Seed Guard and then dry for storage.
Now they are ready to be stored in a cool, dry room where the temperature does not go below 40 degrees F.
If well-ventilated, fruit cellars, heated garages, or potting sheds of greenhouses make ideal storage places for gladiolus corms.
Greenhouse Curing
Those with a greenhouse and space to cure corms are indeed fortunate. Corms cure readily in a greenhouse and benefit from the heat that accumulates under the glass during sunny autumn days.
Use care not to scald the corms by raising the temperature about 90° degrees Fahrenheit. Cover exposed flats during the first week to prevent sunburn. When the greenhouse is well-ventilated, the current is rapid.
44659 by Thomas R. Manley