I love gladiolas. I love vases full of these tall graceful plants that come in a huge array of colors. I mainly plant them as a flower to cut before full bloom. They take awhile to flower and they aren't all that pretty until they do, so I consider the pots I plant with them, cutting flower container gardens. I put them in an out of the way place until they flower, at which point I cut them. After they are cut, they are, not to put too fine a point on it, really ugly so you can either treat them as an annual and chuck the stems and corms (they are like bulbs but different, or you can try to save the corms for next year.
I also tuck some gladiolas into my perennial beds between plants. I don't think you can have too many gladiolas and I wouldn't feel that a summer's gardening was complete without growing bunches.
Here are some tips for growing gladiolas in pots:
- Plant in the Spring - The rule of thumb for glads is that you can plant them when people plant sweet corn in your area. But that assumes you are planting in the ground, where the soil will be much colder than in a pot. Figure that you can safely plant them two weeks before the last spring frost is expected. Sooner, if you want to protect your pot when it gets cold. Glads take seventy to ninety days to flower so factor that in too, when deciding when you want to plant.
- Choose a Deep Pot with Good Drainage - Gladiolas grow to be very tall - some reach three to four feet tall. Even the shorter varieties are tall and narrow, so if you put a lot of them in too short a pot, they can get very top heavy and easily blow over. I have used a large re-usable grocery bag very successfully to grow glads. I figure you want a pot that is at least eighteen inches tall. Also make sure your pot has good drainage. One large hole or several small holes is important so the excess water can get out. Do not use gravel in the bottom of your pot.
- Use Good Potting Soil - Gladiolas like fast draining soil. They don't like to be in soil that is too wet. The corms will rot instead of grow if they are sitting in soggy soil. Also, if your potting soil doesn't have a slow release fertilizer mixed in, add one before you plant. I use an organic, all purpose fertilizer which I mix into the soil, once it is is in the pot. Be sure to follow directions on your fertilizer, particularly if you are using conventional fertilizer, as you don't want to over-fertilize.
- Locate Pot in Full Sun - Gladiolas are sun lovers. They prefer full, unobstructed sun for most of the day, however, they will grow if they get at least 6 hours of sun in the middle of the day.
- Planting Gladiola Corms - Plant your corms three to five inches deep, with the root side down. Also, for a long display, plant a new pot every two weeks, however, keep in mind that they take awhile to grow and flower, so you will need to figure out when your last frost dates are and back date around two and a half to three months from then to find the latest date you can plant. This long growing season means that for many of us with short summers, only one or two plantings are practical.
- Staking and Hilling - These tall skinny flowers often flop over without staking. Once the stalks are about six inches high, you can add soil around them to add to the stability. You can also stake them individually or you can create a corral by using bamboo stakes and string or twine.
- Cut them Early - As soon as the lowest bud starts to show color, you can 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.
- Overwintering Corms - If you are in 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. However, to be honest, I've never had much luck with overwintering gladiola corms. However, if you live in a cold climate and want to give it a try, dig up your corms before before the ground freezes, roughly 8 weeks after blooming. Clean soil off, either by washing or brushing, and cut off the stalk, as close to the corm as possible. Before you try storing, the corms should be completely dry, and may need a couple of weeks, spread out in a, dry, well-ventilated place, before they can be put in mesh bags, or open paper bags or boxes for the winter. They should be stored in a dry, well-ventilated area that is on the cooler side, but that also 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."
- Buying Gladiolas - I buy my gladiolas in the spring when they go on sale. I usually get a huge grab bag from Holland Bulb Farms. You can also order in the fall for spring delivery from many online sites. Also, if you want to buy them in the spring, most local garden centers and big box stores carry them.