Introduction
There is nothing quite like the sight of gladiolus spikes standing tall in the summer garden. These "sword lilies" bring a dramatic flair and a rainbow of colors that make every garden feel like a professional floral display. Whether you grow them for vibrant backyard borders or as elegant cut flowers for your kitchen table, gladiolus are a true summer highlight. At Longfield Gardens, we want to help you enjoy these stunning blooms year after year with as little stress as possible.
Deciding whether to dig up your gladiolus bulbs—which are technically called corms—is one of the most common questions for home gardeners as the growing season winds down. The answer usually depends on where you live and how you prefer to manage your garden. For some, digging is a necessary part of the yearly rhythm, while others might find it easier to simply start fresh each spring.
This guide will help you determine the best path for your specific garden and provide a clear, step-by-step process for those who choose to save their corms. By understanding your local climate and a few simple storage techniques, you can ensure your favorite varieties return even stronger next season.
Understanding Your Gardening Zone
The most important factor in deciding whether to dig up your gladiolus is your USDA hardiness zone. Most gladiolus varieties are considered "tender," meaning they cannot survive a frozen winter in the ground. In the gardening world, we often refer to these as temperennials—plants that act like perennials in warm climates but like annuals in cold ones.
If you live in USDA zones 8, 9, or 10, your soil rarely freezes deep enough to harm the corms. In these warmer regions, you can usually leave your gladiolus in the ground all year. A simple layer of mulch provides enough protection to keep them cozy until spring arrives.
However, if you live in zones 3 through 7, the winter temperatures typically drop low enough to freeze the ground several inches deep. Because these corms are full of moisture, that deep freeze will cause the cells inside the bulb to burst, leading to rot. In these cooler zones, you have two choices: treat your gladiolus as annuals and buy new ones each year, or dig them up and store them indoors for the winter.
What About "Hardy" Gladiolus?
There is a smaller group of gladiolus, often called Gladiolus nanus or "Hardy Glads," that are slightly tougher than the standard large-flowered hybrids. These varieties can sometimes survive the winter in zones 5 or 6 if they are planted in a well-drained spot and covered with a thick layer of mulch. If you aren't sure which type you have, it is always safer to assume they are tender hybrids and plan accordingly. For a broader overview, see our All About Gladiolus.
Why You Might Choose to Dig Them Up
If you live in a cold climate, you might wonder if the effort of digging is worth it. While buying new corms each year is an easy option, there are several wonderful reasons to lift and save your own.
Protecting Special Varieties
If you have found a specific color or bi-color variety that you absolutely love, digging them up is the only way to guarantee you have that exact plant again next year. While we offer a wide range of beautiful options each season, saving your favorites ensures your garden design remains consistent.
Saving Money and Resources
Gladiolus are excellent multipliers. When you dig them up, you will often find that the single corm you planted in the spring has grown and even produced tiny "baby" corms around the base. By saving these, you are essentially growing your garden for free. Over a few years, a small handful of corms can turn into a massive collection.
Preventing Overcrowding
Even in warm climates where gladiolus can stay in the ground, it is a good idea to dig them up every few years. As the corms multiply underground, they can become crowded. This competition for nutrients and space often leads to smaller flowers or fewer blooms. Digging them up allows you to space them out and refresh the soil.
Key Takeaway: Digging up your gladiolus is the best way to save your favorite varieties and expand your garden for free, especially if you live in a region with freezing winters.
When Is the Best Time to Dig?
Timing is everything when it comes to lifting corms. You want to give the plant as much time as possible to store energy, but you must get them out of the ground before the winter weather becomes too severe.
The leaves of the gladiolus act like solar panels. After the flowers have faded, the green foliage continues to pull in energy from the sun and store it in the underground corm. This stored energy is what fuels next year’s growth and flowers. If you cut the leaves off too early, the corm may be too weak to bloom again.
Ideally, you should wait until the foliage has started to turn yellow or brown. This usually happens about six to eight weeks after the flowers have finished blooming. In many parts of the country, this aligns with the first light frost of the autumn. A light frost will kill the top of the plant but won't freeze the soil. This is a perfect signal that it is time to grab your garden fork.
If a hard freeze is predicted (temperatures staying below 28°F for several hours), do not wait for the leaves to turn yellow. It is better to dig them up a little early than to let the corm freeze in the ground.
How to Dig Up Gladiolus Bulbs: Step-by-Step
Lifting gladiolus is a straightforward task that doesn't require any fancy tools. A garden fork or a sturdy spade is usually all you need.
1. Loosen the Soil
Start by inserting your garden fork into the soil about six inches away from the base of the stem. You want to go wide to avoid accidentally stabbing or slicing the corms. Gently rock the fork back and forth to loosen the earth.
2. Lift the Clump
Once the soil is loose, lift the entire plant upward. You can use the stem as a handle, but be gentle. If the soil is heavy or clay-like, it might cling to the corms. Carefully shake off the large clumps of dirt.
3. Inspect the Corms
Once the corms are out of the ground, take a quick look at them. Healthy corms should feel firm and look relatively clean. If you see any that are mushy, shriveled, or show signs of heavy mold, it is best to discard them immediately. This prevents any potential issues from spreading to your healthy corms during storage.
4. Trim the Foliage
Use a pair of clean garden shears to cut the stems off. You should leave about an inch of stem attached to the top of the corm. This small "handle" will dry up during the curing process and eventually fall off on its own.
Action Summary: Digging Your Corms
- Wait for foliage to yellow or for the first light frost.
- Dig at least six inches away from the stem to avoid damage.
- Shake off excess soil but do not wash the corms with water.
- Trim the stems to one inch and discard any soft or damaged corms.
The Curing Process: Preparing for Storage
You cannot move gladiolus corms directly from the damp soil into a storage box. If you do, the trapped moisture will cause them to rot within weeks. Instead, the corms need to cure.
Curing is simply a fancy word for letting the outer skin of the corm dry out and toughen up. This creates a protective barrier that keeps the inner part of the corm healthy during the long winter months.
Find a Warm, Dry Spot
Place your trimmed corms in a single layer on a tray, a screen, or even a sheet of newspaper. They need good airflow, so do not stack them on top of each other. A garage, a garden shed, or a utility room is usually a great spot. The temperature should be between 60°F and 75°F.
Wait Two to Three Weeks
Let the corms sit undisturbed for about two to three weeks. During this time, the outer husks will become papery, and the soil still clinging to them will dry into a fine dust that is easy to brush away.
Removing the "Pancake"
After a few weeks of drying, you will notice something interesting about the anatomy of the gladiolus. The corm you planted in the spring (the "mother") will be a flat, shriveled disk at the bottom of the new, plump corm that grew this summer. We sometimes call this old corm the "pancake."
Once the corms are cured, this old, spent part should snap off easily with a gentle tug. Discard the old, shriveled bottom and keep the new, healthy top. This is also the time to decide what to do with the "cormels"—the tiny, bead-sized baby corms found around the base. You can save the largest ones to grow into full-sized plants over the next two years, or you can simply compost them if you don't have the extra space.
Perfect Winter Storage Conditions
Now that your corms are clean, dry, and separated, they are ready for their winter nap. The goal of storage is to keep the corms dormant without letting them dry out completely or freeze.
The Ideal Temperature
The best temperature for storing gladiolus is between 35°F and 45°F. This is cool enough to prevent them from sprouting but warm enough to keep them alive. An unheated (but frost-free) basement, a crawl space, or a cool closet in a mudroom often works perfectly.
Choosing a Container
Never store your bulbs in airtight plastic containers. Plants are living things and need to breathe, even when they are dormant. Instead, use one of the following:
- Mesh bags: Old onion bags or nylon stockings are excellent because they allow maximum airflow.
- Paper bags: Standard brown lunch bags work well; just leave the tops open or poke a few holes in the sides.
- Cardboard boxes: Layer the corms with newspaper, dry peat moss, or wood shavings to keep them from touching each other.
A Note on Ethylene Gas
Avoid storing your flower bulbs near ripening fruit, especially apples or pears. These fruits give off ethylene gas, which can damage the flower buds inside the corms and lead to poor blooming next year.
Key Takeaway: Store your cured corms in a breathable container in a cool, dark place (35-45°F) away from ripening fruit to ensure they stay healthy until spring.
Getting Ready for Spring Planting
When the birds start singing and the soil begins to warm up in the spring, it is time to check on your stored gladiolus. Most gardeners wait until the danger of hard frost has passed before planting.
The Spring Check-up
Give each corm a gentle squeeze. They should still feel firm. If any have become completely hollow or very soft over the winter, toss them out. It is normal for them to look a bit shriveled compared to how they looked in the fall, but they should still have some weight to them.
Waking Them Up
Some gardeners like to soak their corms in lukewarm water for a few hours before planting to "wake them up," but this isn't strictly necessary. If your soil is moist and warm, they will start growing on their own very quickly.
Planting for Success
When you are ready to plant, remember the simple rule of depth: plant the corm about four times as deep as its height. For most gladiolus, this is about 4 to 6 inches deep. Planting depth matters because planting them deeply actually helps the tall flower spikes stay upright without needing as much staking later in the season.
Managing Pests and Common Issues
While gladiolus are generally very easy to grow, there is one common pest that gardeners should watch for: thrips. Thrips are tiny, slender insects that love to hide inside the husks of the corms. They can cause the flowers to look streaky or fail to open properly.
If you noticed thrips in your garden during the summer, you can give your corms a little extra protection before storing them. Some gardeners choose to dust their cured corms with a gentle insecticidal powder or a light coating of sulfur dust. This helps prevent pests and fungus from taking hold during the winter. If you ever have a question about product quality, our About Us & Our Guarantee page explains how we stand behind our bulbs and plants.
Another simple trick is to keep your storage area as clean as possible. Removing any old garden debris and ensuring your corms are completely dry before they go into bags will solve the vast majority of storage problems.
Summary of the Annual Cycle
Gardening is all about working with the rhythms of nature. For gladiolus, that rhythm is a cycle of bright summer growth and quiet winter rest.
- Spring: Plant your corms in full sun once the soil is warm.
- Summer: Enjoy the tall, colorful spikes and cut a few for indoor vases.
- Autumn: Wait for the foliage to yellow, then lift the corms before the ground freezes.
- Winter: Cure the corms in a warm spot, clean them, and store them in a cool, dark location.
If you are planning a larger bed, our Spring-Planted Bulb Bulk Buys page is worth a look. By following these simple steps, you can turn a one-time purchase into a lifelong collection of beautiful flowers. Whether you are a beginner or a seasoned pro, the process of saving and replanting these summer favorites is one of the most rewarding parts of the gardening year.
Conclusion
Deciding whether you should dig up gladiolus bulbs ultimately comes down to your climate and how much you enjoy the process of tending to your plants. While it does take a little bit of time in the autumn, the reward of seeing your favorite colors return to the garden each year is well worth the effort. At Longfield Gardens, we believe that gardening should be a joy, and saving your corms is a wonderful way to connect with the life cycle of your backyard.
If you live in a cold zone and choose not to dig, don't feel guilty! Many gardeners prefer the ease of treating gladiolus as annuals and trying out fresh new colors and varieties every spring. There is no wrong way to garden as long as you are enjoying the results.
- Know your zone to determine if digging is a necessity or an option.
- Cure your corms thoroughly to prevent rot.
- Store them in a cool, breathable spot over the winter.
Ready to start planning for next year? We invite you to browse our selection of premium gladiolus and other summer-blooming bulbs to find the perfect additions to your landscape.
"Saving your own gladiolus corms is like putting a little bit of summer magic into a box to be rediscovered next spring."
FAQ
Can I leave my gladiolus in the ground if I live in Zone 7?
Zone 7 is often considered a "swing" zone for gladiolus. In a mild winter with well-drained soil and a thick layer of mulch, they may survive. However, a particularly wet or cold winter can cause them to rot. If you have a variety you truly love, it is safer to dig it up.
Do I need to wash the dirt off the bulbs before storing them?
It is actually better not to wash them. Introducing extra moisture can encourage rot and fungal growth. Instead, let the corms dry (cure) for a couple of weeks, and the dried soil will brush off easily without the need for water.
Why didn't my saved gladiolus bloom this year?
The most common reason is that the corm didn't store enough energy the previous year. This happens if the foliage was cut back while it was still green or if the plant was grown in too much shade. Make sure to let the leaves turn yellow before digging and plant them in full sun.
How long do gladiolus corms last in storage?
If kept in the proper cool and dry conditions, corms will last through the entire winter until spring planting time (about 5 to 7 months). They cannot be stored for a full year, as they will eventually dry out completely and lose their ability to sprout.
