This section is from the book "The Florists' Manual", by William Scott. Also available from Amazon: The Florist's Manual.
The varieties we grow are hybrids from some of the many species of which the large genus is composed. The handsome spikes of the gladiolus are known to all, and for the flower border the gladiolus is one of the most handsome of summer flowers, but grown with such ease by every one that the price of the spikes is now very low.
Gladioli in a Stone Jar.
They can be readily raised from seed and will flower the second year. That, of course, is the only way to produce varieties, of which now there are legions.
They are often grown by florists on their benches among other crops to produce flowers in May and June before those outside are in bloom. They will not flower, however, till we get the warm days of spring, and no matter how early you may plant the bulbs they will in a carnation temperature grow very slowly. I have never seen that they injured the carnations if not put in too thickly.
Plant the bulb on the bench in February among the carnations by just squeezing it into the soil. It needs no covering and the watering you give the carnations will suit the gladiolus. A rose bench would suit them much better, but it would be hardly fair to the roses.
Out of doors the cultivation is very simple. The better the ground the finer the spikes, and in very dry weather they should get an occasional soaking with water. Very large growers must necessarily use only plow and cultivator. The commercial man should plant the corms (for they are not bulbs at all) in rows two feet apart, so that the horse cultivator can be run between them, and six to eight inches in the rows. Five to six inches deep is about right. When as deep as that they are not in our dry summers so likely to suffer for want of water.
A World's Fair Exhibit Which Did Much to Popularize the Gladiolus.
The corms increase rapidly and you will frequently find two fine ones in place of the old one planted in the spring. If a succession of flowers is desired, make plantings at intervals of two weeks, but remember that you will get no more flowers after the first frost. Before there is any danger of frost reaching the corms, dig them up and let them lie in the sun for a day or two with the tops cut off a foot or so above the corms. When the stalk is dry, cut it off within an inch of the corm, and if they are not wet with rain or dew store them away in flat trays anywhere out of the reach of frost.
Any place that will keep potatoes will keep gladiolus bulbs. There is usually such a place in the greenhouse sheds. They are the easiest possible bulbs to keep; only keep them from frost. We once had a lot dug up and lying on the ground to ripen the tops when over night down came a frost, of about 3 degrees. I thought our gladioli had escaped, but every bulb was destroyed.
The white and light varieties are much the most valuable to the florist. There are now pure white varieties and of every other conceivable shade except blue. In buying bulbs remember that seventy-five per cent should be white or very light shades.
it is impossible to give a list of names. There are too many, and few florists grow them under name. The Lemoine strain is very handsome and distinct and differs from the ordinary gladiolus by being finely spotted and marked, and some of them have fine shades of orange and yellow. Red sells well, also.