GLADIOLUS FLOWERS: GOING GAGA FOR GLADS

Photo by: Shannon Marie Ferguson / Shutterstock.

Botanical name:

Gladiolus xhortulanus

Common names:

Common gladiolus, garden glad, and sword lily (because of the long, pointed leaves)

Zones:

Perennial in zones 8-10. Can be grown as annuals in zones 2-7. Some G. nanus types are hardy to zone 4 or 5.

How they grow:

Although you will often see glads labeled as “summer bulbs,” they are herbaceous perennials that grow from bulb-like corms covered with a fibrous papery skin. Unlike spring bulbs, glad corms are sensitive to freezing temperatures and must be dug up in fall and stored until planting time the following spring. In mild climates, some hardier glad hybrids can be left in the ground over winter.

Types:

You’ll find countless cultivars of glads in local garden centers and catalogs, all derived from various combinations of more than 250 species, most of which are native to southern and central Africa and Eurasia.

The three main glad groups are:

• Grandiflora: The largest group of garden cultivars. These hybrids are the showiest of the bunch, with blooms up to 6 inches wide and the most extensive range of colors.
• Nanus: Another group commonly grown in the garden. Miniature hybrids that tend to be more cold-tolerant than their taller cousins.
• Primulinus: Have daintier hooded flowers and very narrow leaves.

Flower characteristics:

Most garden glads come in nearly any color and shade (except for true blue) in both solid and multicolored forms. Depending on the cultivar, the petals may be frilly, ruffled, semi-ruffled or plain, and the size can range from miniature (under 2 ½ inches in diameter) to gigantic (over 5 inches). The flowers are typically arranged on only one side of the stem and open in succession from the bottom up, with the largest flower at the base. As a bonus, hummingbirds really love these flowers!

Height:

1 to 5 feet

Bloom time:

From early summer until frost, depending on the cultivar and when the corms are planted.

Gladiolus corms ready for planting. Photo by: Longfield Gardens.

When to plant:

You can plant glad corms as early as a month before the average last frost date in your area. Depending on the cultivar, gladiolus take anywhere from 60 to 120 days after planting before they flower. You can stretch the blooming season by making succession plantings of corms at two-week intervals through early July and by intermixing varieties that take different lengths of time to mature. Make your last planting about 12 weeks before the first frost date.

Where to plant:

Depending on your purpose, you can plant glads in flower beds and borders, vegetable gardens, cut flower gardens, and even containers. All they need is a sunny location and one protected from the wind to avoid damage to the tall flower-laden stalks. If you are integrating glads into an established flower garden, use them to fill in spaces that need color or vertical interest. They will begin blooming in late summer when many other flowers begin to fade. In a vegetable garden, plant your glads in rows alongside the rest of your crops or use them to fill in the gaps left behind after you remove early-season edibles, such as peas, lettuce, and spinach.

Planting depth and spacing:

Gladiolus corms can vary in size, depending on the type of glad you’re planting. As with other bulbs, the larger the corm the deeper and farther apart it goes into the ground, ranging anywhere from 2 to 6 inches. For the best results, follow the recommendations given on the package. Always plant corms with the flatter side facing downward, and the narrower, pointed end facing up.

Soil:

Glads aren’t fussy and will thrive in many different soil types, but good drainage is a must. Before planting each spring, work the soil several inches deeper than the planting depth of the corm and amend it with organic matter if necessary. Loose, well-tilled soils that produce good vegetable crops are often perfect for growing gladiolus.

For more on planting and storing bulbs:

Bulbs 101

Staking:

Glads that grow 3 to 4 feet or taller will probably need to be staked or caged to prevent the stalks from bending and breaking. You should set the stakes in the ground at planting time to avoid damage to the corms.

Watering:

After planting, water glads thoroughly and then keep the soil evenly moist throughout the growing season. During dry weather, soak the ground thoroughly to supply the equivalent of an inch of rainfall per week. To help conserve moisture and control weeds, apply a 2- to 4-inch layer of mulch around your plants. (See How to Mulch and Avoid Mistakes.)

Pest problems:

The biggest threat to gladioli are thrips, tiny flying insects that feed on the foliage and flower buds. Because thrips are hard to spot without a magnifying glass, watch your glads for signs of thrip damage, which includes silvery streaks and small white patches on the leaves and buds that fail to open. See these tips from bulb supplier Old House Gardens for identifying and getting rid of thrips.

Winter storage:

After a glad blooms, the original corm begins to wither away and a new one forms for the next year’s growth. In areas where gladiolus aren’t hardy, you can overwinter the newly formed corms until the following spring by digging them up in fall once the foliage has been killed by frost. Here are the basic steps:

• Cut the stalk off just above each corm, brush or wash off the soil, and then allow the corms to dry in a well-ventilated area for a couple weeks.
• Separate the new corms from the old one, and store them in a dark, dry, cool area. Ideal storage temperatures are just above freezing (between 35° and 45° F). A good method of storage is to layer them in a cardboard box with newspaper in between, a paper bag would also work.
• Some corms also produce cormels -- smaller plantlets that can be separated from the parent and grown into new plants. However, cormels often won’t produce blooms for several years until they grow larger and are best discarded unless you have the patience to save them and replant them each spring.
• If you have a variety of glads, label the corms by color or cultivar before storing them so you know what you’re planting the following spring.
• Check your corms periodically to make sure they are in good condition. If they have started to sprout new growth, move them to a cooler spot. If you notice signs of rot, the packing material may be too moist.
• If you don't want to fuss with digging up and storing the corms each year, simply treat them as annuals and buy new ones every spring. The most common glad cultivars are inexpensive and widely available, so it’s often more cost effective to replace them, especially if you factor in the time you’ll save.