How to Grow Gladiolas in Pots

Gladiolus' tall graceful spikes come in a huge array of flower colors and are long-time favorites of novice and professional gardeners alike. However, before the flowers are in bloom and after the blooms have faded, the plants themselves are not particularly attractive—their sword-like foliage is unremarkable, and the plants can make an otherwise beautiful garden bed look rather messy and unkempt.

Many gardeners learn to plant gladiolus among other flowers to disguise them until their spectacular bloom period. But there's another solution—by planting gladiolus in containers, you can place the growing plants wherever you want until they bloom and are ready for you to harvest for cut arrangements. Once cut, you can then either treat them as an annual flower and discard the stems and corms, or let the foliage fade, then dig up and save the corms for replanting next year. Here are some tips for successfully growing gladiolus in pots.

When to Plant Gladiolus in Pots

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. If you are not a vegetable gardener, this means that garden gladiolas should be planted about two weeks before the last spring frost. Gladiolas require 70 to 90 days to flower, which means that corms planted at the beginning of May will flower in mid-to-late summer. Gladiola enthusiasts often stagger plantings every two weeks to ensure a supply of flowers for cutting throughout the summer and early fall months.

However, when planting your gladiolus in pots, you can plan to plant them even sooner, as the soil in pots warms up much faster than the soil in the ground. You can plant up to four weeks before the last expected spring frost, provided you are willing to protect the plants on the inevitable nights when frost is still expected.

How to Pot Gladiolus

Gladiolus is a fairly forgiving varietal, and corms purchased from reputable nurseries and garden centers are usually hearty and easy to grow. They do have some important requirements, however, in order to thrive in your potted garden. Here's how to care for them properly:

1. Choose a tall enough pot: Gladiolus can grow to be very tall—some reach 3 to 4 feet in height—but their root systems are not very robust. Because their typical planting depth is only about three to five inches, you will need to drive deep stakes into your soil in order to help support the stalks. Gladiolus planted in short, squat pots will still grow, but without the support of long stakes they can easily blow over. Choose a pot that's at least 12 inches deep to accommodate your gladiolas, guaranteeing there is at least 2 to 4 inches of soil below the corms.
2. Provide good drainage: Make sure your chosen pot has ample drainage holes. If the soil remains wet, the corms will most certainly rot. Some gardeners even place one to two inches of gravel in the bottom of the container (covered with a layer of landscape fabric) to prevent the soil from draining down and clogging the drainage holes. Additionally, you can opt for a clay or terracotta pot to help wick excess moisture from the soil.
3. Use the proper potting soil: Gladiolus like fast-draining soil so their roots don't sit in water, so be sure to choose high-quality, loamy potting soil. If your potting soil doesn't already include a slow-release, all-purpose fertilizer, add one in before you plant.
4. Plant the corms three to five inches deep, root side down: The corms will usually have one or more "eyes" on top, sometimes found under a papery corm tissue; these are the future plant stalks, so this is the side that should face up. For a season-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 between 70 to 90 days to grow and bloom, so if you have short summers, you may be able to get in only one or two plantings.
5. Position the pot in full sun: Gladiolas are sun lovers. They prefer full, unobstructed sun for most of the day, but will still grow provided they get at least six hours of sun in the middle of the day. One of the advantages of planting them in pots is that you can move them around as sun patterns change throughout the day (and season) to ensure they get plenty of light.

Caring for Gladiolas

Potted gladiolas are fairly easy to care for if you follow some simple tips:

• Stake and support: These top-heavy flowers will flop over unless you stake them. Once the plant stalks are about 6 inches high, pack soil around their base to improve their stability. You can also stake the stalks individually or create a corral by using bamboo stakes with string or twine.
• Water heavily once a week: A single soaking once a week is much better than light waterings several times a week. After you cut the flowers, continue to water the foliage and corms until the leaves begin to dry up and turn brown.
• Cut them early: Gladiolas are ready to be cut as soon as the lowest buds on the stalk start to show color. Cut the stems on an angled bias and quickly put the flowers into water. For longer-lasting blooms, change the water in your vase daily.
• Leave the foliage in place: After cutting, the corms will replenish themselves if you allow the foliage to remain in place until it turns brown and dries up, at which point you can dig them up and save them for the following year. If you plan to discard the corms instead, you can remove and dispose of the foliage and stalks immediately.

Overwintering Gladiolas

If you live in USDA hardiness zones 7 and 8, you may be able to overwinter your gladiolas right in the pot by mulching them with hay or straw. You can also try putting the whole container in a dark, cool indoor space for the winter.

In colder climates, you can try to overwinter your gladiolas by digging up the 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. Gladiolas normally form new corms on top of the old corms; you will be discarding the shell of the old corm and saving the fresh, new corm for replanting. You may also notice a few small offshoot corms—"baby" corms or cormlets—attached to the main corm. These can be saved and replanted, though it may take several years before they are mature enough to produce flowering plants.

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—a basement or garage works well, so long as it maintains a temperature between 38 and 58 degrees Fahrenheit.