Daffodils, tulips, and many other types of flowering bulbs need to chill in the ground to rebloom season after season. But the bulbs of plants such as dahlias, gladiolus, tuberous begonias, caladium, cannas, and calla lilies are not cold hardy in the temperate zones of the US. To keep them going, you can dig them up, keep them inside, and replant them the following spring, saving you money and adding more flowers to your landscape. Here’s what you need to do to preserve tender flower bulbs from season to season.
1. Timing: When to Dig Up Your Bulbs
Lift with care. After the first frost in fall kills the top growth of the plants, it’s time to dig up the bulbs, which, botanically speaking, may actually be corms, rhizomes, or tubers. Loosen the roots gently by digging several inches back from the base of the plant on all sides. Avoid cutting or bruising the bulbs or rubbing off the outer skin of dahlia tubers. Damaged bulbs are susceptible to rot, diseases, or dehydration.
Trim the tops. Cut off any remaining foliage and compost it. Snip the leaves close to the top of the bulb but avoid cutting into the bulb.
2. Preparing the Bulbs for Storage
Don’t wash. Rinsing the bulbs can leave them damp and prone to problems. Just allow the soil on them to dry.
Cure for days. Spread out the bulbs on a window screen or another surface that allows air to circulate around them. Place them in a cool, dry spot away from direct light.
Brush clean. After about a week, check to see if the bulbs are thoroughly dry. If they are, use your fingers to gently loosen and rub off any chunks of soil attached to the bulbs.
3. How to Store Tender Bulbs
Fill the container. Spread a couple inches of dry material such as peat, sand, pine straw, or shredded paper on the bottom of a plastic container with a tight-fitting lid. Use a separate box for each type of bulb, unless you are certain you can identify them later.
Layer the bulbs. Arrange your bulbs in a single layer, making sure that they are not touching, which can lead to rotting. Add another layer of dry material on top, then more bulbs. If you have more than three layers of bulbs, use a larger box.
Label to remember. Put a piece of masking tape on the boxes and list the types of bulbs in each box. This will make it easier for you to take them out at the right time the following season.
Store inside. Set the container in a cool, dry spot, such as a basement or closet. Just be sure you can reach the boxes during the winter.
4. Monitor Your Bulbs Over Winter
Check for rot. About once a month during the storage period, open the boxes and inspect each bulb. Pick them up and give them a light squeeze to be sure they are still firm. If they have shrunk or are wrinkled, they may be dehydrated. Moisten the layering medium a little (such as with a spray bottle) and re-pack them. If they are too damp, remove them from the packing material and air dry for a few days before repacking in dry material.
Discard problems. Toss any bulbs that have soft spots or show other signs of rotting into your compost pile. If you leave deteriorating bulbs in the box, the rot may spread to others.
5. Preparing Bulbs for Replanting in Spring
Wait for spring. When the soil has warmed up to 60 degrees F, bring your boxes of tender bulbs out of storage.
Look them over. Some types of bulbs will begin to resprout after a few months in storage, while others remain fully dormant. Be careful not to damage any new shoots. Compost any that have rotted in storage.
Pot or plant. You can give the bulbs a head start by putting them in a container with potting mix a few weeks early.