When to Plant Gladiolus Bulbs: 7 Planting Tips
Gladiolus bulbs are perfect for gardens with short growing seasons! Plant them in spring for midsummer blooms. With proper preparation and succession planting, you’ll cultivate healthy, gorgeous blooms all summer. Join backyard gardener Jerad Bryant in getting your gladioli in the ground with these seven tips.
Contents
There are two types of garden bulbs: spring-blooming and summer-blooming. Spring bloomers, like daffodils, tulips, and snowdrops, grow in the ground during winter and emerge in early spring. Summer bloomers, like gladioli and tuberous begonias, benefit from spring plantings.
After transplanting, the summer bloomers emerge with new green shoots. They’ll gather energy during spring before pushing out long, decorative, and showy flowering spikes as the growing season progresses. Proper transplanting ensures the flowers quickly fill empty spaces in the garden.
Though we call gladiolus “bulbs,” they’re actually corms! Corms are like bulbs, except they lack the sheathed layers that bulbs produce. Corms are swollen stems stuffed with storage tissue; they typically have a single outer layer and a swollen inner portion.
So, how and when do you plant gladiolus corms/bulbs? Let’s get into it!
Prepare the Soil
Proper preparation is key to growing gladioli successfully! Once you establish when you plan to plant the gladiolus bulbs/corms, consider your garden’s soil a few weeks or months in advance. These flowering plants benefit from fertile, well-drained soil free of large clay clumps.
If your soil is extremely clay-heavy or full of sand, consider amending the site with organic matter. Mulches like compost, leaf mold, and wood chips insulate the ground while they feed it with microbes, nutrients, and worms.
To prepare the soil, add a two to three-inch thick layer of compost in the fall. Let it break down during winter, and you’ll have crumbly, fertile soil after the last average frost date. If you forget to amend in the fall, simply add mulch as soon as the ground is workable in late winter or early spring.
Source Healthy Corms
Finding healthy planting stock ensures you grow as many flowers as possible! You want to purchase corms that are swollen, perky, and large. Avoid planting the tiny offshoots that form underground. Called “cormels,” they require a few years of growth before they bloom.
Certified pest and disease-free corms are the best types to purchase. Pests can spread from the stock into your garden and harm future plantings. By sourcing disease-free plants, you avoid bringing these pathogens to your yard.
You also want to choose gladioli you’ll enjoy growing! They come in all shapes, sizes, and colors. Try ‘Jester’ for bright yellow blooms with orange throats, or opt for ‘Flirty’ for lavender blossoms. No matter which type you select, you want large, healthy corms free from punctures, wounds, or pests.
Wait Until After the Last Frost
Unlike daffodils and tulips, gladiolus plants are sensitive to cold temperatures and frosty weather. They’re perennial in USDA hardiness zones 7 through 10 but benefit from overwintering indoors in all other zones. Like dahlias, tuberous begonias, and lilies, gladiolus plants require protection from late and early frosts to grow well.
You may safely plant the gladioli’s bulb-like structures when the danger of frost passes in your region. This happens a week or two after your last average frost date for most gardeners. Sometimes, late spring frosts arrive that threaten your growing flowers. It’s best to wait until the weather is cool and mild for planting.
Some growers plant them a month before the final frost date! If you garden in zones 6 and 7 and have a mild winter, you may experiment with early planting without worrying about losses. Just know that a surprise frost can damage your gladiolus plants or set their bloom period back.
Dig a Sizable Hole
Once you’re ready to plant, the next step is to prepare the planting hole. A large, deep hole ensures the plants have a healthy start early in the growing season. The site is also important; these perennials benefit from rich, fertile, and free-draining soil. They need a site with full sun or at least six hours of daily direct sunlight.
After choosing a viable site, it’s time to dig a hole. Dig about five inches deep and make the hole a little wider than the corm. When planting multiple gladiolus bulb-like structures, separate them so they have five inches of space between them. The mature plants have significant root systems and stems that may crowd each other if they’re too close.
Though some guides urge you to amend the planting hole, this practice leads to weak root systems and poorly performing plants. Avoid putting compost or mulch directly into the hole; instead, add it on top of the soil after planting.
Plant Gladiolus Corms
Here comes the fun part! Planting is the easiest step. Simply place the bulb-like roots in the holes right side up. The pointed tip is the top, while the flat portion is the bottom. Some may have sprouts at their tops; take care not to damage them during the planting process. The sprouts turn into flowering spikes later in the season!
Cover the plants loosely with soil, then water them in well. You want the ground to be moist like a wrung-out sponge and not too soggy. Many gardens have frequent rains in spring; if your area is moist and cool, let the rains water your fresh plants.
After planting, your gladioli need eight to ten weeks to flower. They’ll produce strappy, swordlike leaves that photosynthesize and gather energy for future blossoms. Never prune the leaves in spring unless they have pests, diseases, or wounds. The plants need these leaves to form their flowers.
Plant More Corms!
Because these bulb-like perennials need eight to ten weeks to flower, it’s beneficial to plant them throughout the growing season. From spring until early summer, continuously bury gladiolus varieties for a never-ending show of blooms.
To succession plant, bury corms every two weeks until midsummer. For many growers, the last month for planting is July, though it can be sooner or later depending on your climate. If your first average frost date happens in eight to ten weeks, it’s too late to plant gladiolus varieties.
Growers in zones 7 through 10 will see their plants bloom all at once rather than staggered throughout the season. To trick them, you’ll need to dig them up for overwintering. Then, you can plant them successively every two weeks from spring through summer for staggered blooms.
Care for Growing Gladioli
Your budding flowers appreciate consistent care while they mature. If late frosts are projected, use frost cloth or row cover to protect the young plants. Late frosts can halt their growth, causing the flowers to appear much later in the season.
It’s also important to ensure the site stays moist and not soggy while they grow. Always grow them in well-drained soil to prevent moisture from sitting around their crowns. Adding compost twice a year is an easy way to help with drainage and water absorption. Make a two to three-inch thick layer after you bury the plants and again in fall before winter frosts arrive.
Mulching in the fall can help the species survive the winter, as the extra insulation protects them from winter ice, snow, and frost. Other possible mulches include fall leaves, wood chips, and straw.
