Storing bulbs over the winter is a great way to continue enjoying the beauty of their flowers! Certain plants flower and reproduce from a bulb. When the herbaceous plant is not in bloom, all its energy is stored in a small tuber that can fit in the palm of your hand. You can actually dig up the bulb at the end of the growing season and replant the same one the following spring! While some plants may not be adapted to the cold of North American winters, they are eager to come back the next year if they have a cozy place to spend the winter. Learn how to store bulbs over the winter using our comprehensive guide here.
What is a bulb?
The term “bulb” generally refers to a fleshy part of a plant, including the bulbs, corms, rhizomes, tubers, and roots. All these structures store water and nutrients to support the plant during its growing season and its winter dormancy. A botanist or academic horticulturist will describe the physical and functional differences of each of these plant organs. But for the sake of this article, we will lump them all together with the term “bulb” – a similar tactic to lumping culinary vegetables together even though many are technically fruit.
Types of Bulbs
The two types of bulbs are hearty bulbs and tender bulbs. While hearty bulbs sleep happily under snow-covered soil and can be planted in the fall, types of plants that we’ve adopted from tropical and subtropical climates don’t fare quite as well. Tender bulbs are not winterhardy, meaning they cannot survive cold temperatures outside and must be planted in the spring.
|Planting Season||Blooming Season||Examples|
|Hearty Bulbs||Fall||Spring||Tulip, Crocus, Daffodil, Hyacinth, Iris, and Snowdrop|
|Tender Bulbs||Spring||Summer||Amarylis, Dahlia, Canna Lily, Gladiolus, and Begonia|
Caring for tender bulbs involves digging them up before the temperate winter temperatures settle in. Think of this process as hibernation for your plants. But instead of finding a cozy hollow log or cave like a bear, the bulbs need a bit of human help to cozy up for the cold months. Here are the general steps and best practices for storing bulbs over the winter.
Steps to Storing Bulbs Over the Winter
While you can’t quite plant them and forget them, they are slightly different than your classic annual. You can dig up the bulbs each fall and store them in a more amenable climate until spring. The steps to caring for your bulbs over the winter:
1. Digging Up the Bulbs
The process of storing bulbs begins with digging them up from the soil. The trick to digging up bulbs lies in the timing. Dig your bulbs too early and they haven’t stored enough starch in the bulb to survive dormancy. Dig them too late and the bulb might be killed by the cold. There are a couple of clues to look for that indicate when they are ready to be dug. In general, look at the plant’s foliage. If the leaves have turned yellow, dried up, or been killed by the frost then it’s time to get out your gardening gloves! Another clue is the timing. Waiting about six to eight weeks after blooming gives the plant enough time to assimilate the nutrients in the bulb.
Once the plants are ready, use a garden fork or small spade to begin gently loosening the roots. To avoid cutting into the bulb or severing roots, start digging several inches away from the base of the plant. Take a lot of care here! Creating cuts or breaking the bulb can cause the plant to rot or become vulnerable to disease. If the plant is on the larger side, loosen all the dirt around the plant before trying to extract the bulb. Overall, working slowly and gently to loosen the dirt is the best way to dig up bulbs.
2. Cleaning the Bulbs
After digging the bulbs, they will be covered in dirt, so the next step of storing the bulbs is cleaning. However, cleaning is not a one size fits all situation. Different plant species require different strategies. To wash dahlias, for example, spray them gently with a hose. Canna lilies can be cleaned the same way! Gladiolus and begonia bulbs, however, don’t do well with water. Washing them with a hose can make it more likely for a fungus infection. After you’ve dug them up, you can go straight to curing, then brush off excess dirt once they are dry. In conclusion, clean the dirt off by either spraying them with water or brushing it off the dried bulb. Do your research on the specific plant to keep it as healthy as possible!
Curing refers to drying out the bulbs. An important part of the storing process, dehydrating the bulbs reduces the chance of fungal infection or disease. Imagine throwing a bunch of fresh grapes in a box in your basement. It would turn into a moldy disaster in a few days. Raisins, on the other hand? They have a much longer shelf life!
Like cleaning, the curing process depends on the type of bulb. Many species, like dahlias and canna lilies, only need a few days to dry out while others, like gladiolus, need to dry for about three weeks. Sunlight and wind can disrupt and accelerate the drying, so find an indoor space to spread them out to cure. The bulbs will cure at a higher temperature than they need to be stored. Cure them in a room that is between 60-70℉.
4. Storing Tender Bulbs
Finally, your bulbs are ready to store! As you prepare them for their wintry home, consider labeling the bulbs with their species so you remember what they are in the spring. You can even add the specific cultivar, color, or bloom pattern. Tie a label to the root or even write directly on the bulb with a felt-tip marker. Your future self will thank you!
Only storing large, healthy bulbs will ensure a sneaky fungus won’t overtake the box and you won’t be disappointed in the spring. Additionally, damaged or bruised bulbs may rot and tiny bulbs might completely shrivel. If you remember throughout the winter, periodically check on your bulbs and remove any that look like they are starting to rot. Finally, pack the bulbs in a box with some cushioning. Using a material like peat moss will keep the bulbs from touching, reduce the humidity, and prevent rot. Wood shavings can make a decent choice too, but wood chips will damage the bulbs.
Temperature and humidity are key to healthy storage for your tender bulbs. In general, cool and dry conditions are ideal with an average temperature of around 40-50℉. However, many of the plants come from the tropics! Certain species prefer to be kept at a warmer or more specific temperature. For storing bulbs beyond the backyard garden, using a walk-in cooler allows you complete control over the temperature and humidity of your bulbs. If you run a gardening center or floral shop, reach out to the folks at Coolbot to find a unit that best fits your bulb storage needs!