Gladiolus are grown from corms, and the corm contains all the necessary food and energy to produce a glorious flower spike with up to 20 florets on each bloom. Start by selecting a planting site that receives full sun and has fertile, well draining soil. You can either choose to dig individual holes for your gladiolus corms, or you can dig a large planting area and place multiple corms in that hole. Either way, plant the corms 4-5 inches deep and leave 3 inches of space between each corm. For a truly spectacular display in the garden, I like to plant mine in groups of 7 or more...I think planting gladiolas in masse gives the look of a beautiful living bouquet in the garden.. Once your hole is dug, place the corms pointy side up, flat root side down in the hole and then cover them back up with soil. Once all your corms are planted be sure to water them in well. In a few short weeks the strong and spiky foliage will emerge from the ground and at that time it's a good idea to give them a light layer of mulch to help suppress weeds and maintain even moisture levels during the growing season.
Gladiolus appreciate consistent water. During dry weather, water the plants deeply to supply the equivalent of 1 inch of rainfall per week. If you notice that the blooms are becoming heavy and starting to lean give them a little support by placing a slender bamboo cane next to the stem and use twine to secure the bloom stock to the cane. If you need to support a large section of gladiolas you can corral them with multiple canes and twine encircling the entire planting area.
I personally love to use my gladiolus as cut flowers, and when you use them for cutting you normally avoid the leaning altogether since you pick them before they become top heavy. Gladiolas bloom from the bottom to the top, and for the longest vase life we want to harvest them when the bottom two florets on a stem are open. You should also remove the tip of the flower to encourage all the other flowers on the stem to open in the vase. As lower flowers fade, simply pull them off, and enjoy the new ones that will continue to open.
I also find that it's a nice idea to succession plant gladiolus throughout the growing season so that you can enjoy a steady supply of blooms. So start planting in spring after all danger of frost has past, and then continue to plant a wave every week or two for continuous blooms. Since they take approximately 90 days to mature, count back about 3 months from your first expected frost date and have that day be your last planting of gladiolus corms.
Now let's talk about what to do with gladiolus after they're done blooming. Since gladiolus corms are hardy in zones 7-10, growers in those areas can leave the corms in ground to perennialize. Simply let the plant die back naturally in the fall and then cut it down to ground level once it has browned. It will come back again for you next year with no additional work on your part. However, growers in zones 3-6 should either treat gladiolus as annuals and plant new corms each year, or they can be dug up in fall and stored until planting next spring. In this case, after the first frost, dig up the corms and allow them to dry (cure) in a warm, dry, well ventilated area for 2-3 weeks. When thoroughly dry, remove and discard the old dried up mother corm located at the base of the new corms. You can either remove the tiny cormlets found around the base of the new corms, or use them for prorogation purposes. Once cured, place the corms in mesh bags or old nylon stockings and hang in a cool, dark, well-ventilated location with an ideal storage temperatures of 35 to 45 degrees Fahrenheit. Next spring, simply remove them from storage and replant them.