Gladiolus' tall graceful spikes come in a huge array of colors and are long-time garden favorites. But before the flowers are in bloom and especially after you have cut off the bloom, the plants themselves are not particularly attractive. In fact, they can make an otherwise beautiful garden bed look messy and debris-cluttered.
The solution is to plant them in containers where you can place the growing plants anywhere you want until they flower and you cut them for that nice vase on your dining room table.
Once cut, either treat them as an annual and discard the stems and corms, or save the corms for next year.
Here are some tips for growing gladiolus (also colloquially called gladiolas or just glads) in pots.
When to Plant Gladiolus
The rule of thumb for gladiolus is to plant them at the same time you would plant sweet corn in your area — assuming you are planting in the ground, where the soil is much colder than in a pot. For pots, a safe estimate is two weeks before the last spring frost is expected, or sooner, if you want to protect your pot when it gets cold. Glads take 70 to 90 days to flower, so be sure to factor that in when deciding when you want to plant.
How to Pot Your Glads
Gladiolus are fairly forgiving and the corms from reputable nurseries are usually hearty and easy to grow. They do have some important requirements, however, to thrive in your garden.
Choose a pot tall enough to support them.
Glads grow to be very tall — some reach three to four feet. Even the shorter varieties are tall and narrow, so if you put a lot of them in a squat pot, they can get top heavy and easily blow over. Try to use a pot that is at least 18 inches tall. One option is a re-usable grocery bag which has the depth (and girth) to easily grow several glads.
Provide Good Drainage. Make sure your pot has good drainage — if the soil remains wet, the corms will rot. Ensure that the pot has one large hole or several small holes so excess water can drain out. Do not use gravel in the bottom of your pot because water doesn't drain through gravel nearly as quickly as soil.
Use Good Potting Soil. Glads like fast-draining soil so their roots don't sit in water, so be sure to choose high-quality, loamy soil. Also, if your potting soil doesn't include slow release fertilizer, add one before you plant. Use an organic, all-purpose fertilizer and mix it into the soil once it is in the pot. Be sure to follow application directions, particularly for conventional fertilizers, as you don't want to over-fertilize.
Plant the Corms three to five inches deep, with the root side down. If you can't determine which side is which, plant them on a side, and plants will figure out what to do. For a long display, plant a new pot every two weeks — however, be aware of the first frost date in the fall for your area. Glads take from 10 to 12 weeks to grow and bloom, so for many of you with short summers, only one or two plantings are practical.
Locate the Pot in Full Sun. Gladiolus are sun lovers.
They prefer full, unobstructed sun for most of the day; however, they will grow if they get at least six hours of sun in the middle of the day.
How to Care for Your Glads
Stake and Support. These tall, skinny flowers often flop over without staking. Once the stalks are about six inches high, add soil around their base to improve stability. You can also stake them individually or create a corral by using bamboo stakes and string or twine.
Cut Them Early. As soon as the lowest bud starts to show color, cut your gladiolas. Cut them on a bias and quickly put them in water. For long lasting blooms, change the water in your vase daily.
How to Overwinter Corms
For zones 7 and 8, you may be able to overwinter your gladiolas by mulching them with hay or straw. You can also try putting the whole container in a dark, cool space for the winter.
Overwintering gladiola corms is not a sure thing, but if want to give it a try, dig up your corms before the ground freezes, roughly eight weeks after blooming. Clean off the soil, either by washing or brushing, and cut off the stalk as close to the corm as possible. Ensure that the corms are completely dry before storing them in mesh bags, open paper bags or boxes for the winter. Store them in a dry, well-ventilated, cool area that doesn't freeze. According to the North American Gladiolus Council, "A well-ventilated root cellar is ideal but any room with good air circulation in the average home basement will suffice, if temperatures can be kept between 38 - 58 degrees. The lower temperature is best."