Have you ever wondered where to store bulbs and tubers over the winter months to protect them? Let’s discuss bulb storage solutions to protect them from critters, heat, frost, and general rot so you can plant them again in the spring.
An ideal storage location should be a dry, cool place away from pests and critters. Temperatures must remain between 40-45°, and containers must provide proper ventilation.
Bulbs and tubers are modified root structures where certain plants store nutrients to ensure they survive the winter and propagate in spring. As gardeners in colder zones, we aid this process by storing tender bulbs in protected conditions rather than leaving them outside.
But there’s nothing worse than going through the tenuous work of digging and storing at the end of the season, only to find pest disturbance, critter damage, or loss to humidity and freezing temperatures when you check your bulbs in spring.
Let’s discuss the critical elements for successful winter bulb storage to yield the best results in spring.
What Are Bulbs and Tubers?
Tubers and bulbs store energy for dormancy.
It’s important to know that tubers and bulbs are energy storage for certain ornamental and edible plants. They go dormant during winter, surviving off the stored sugars until spring when they return to life. While some look sort of like onions and others look like a funky sweet potato, they are all similar in functionality.
Bulbs are modified stems with leaves. They contain flowers in embryonic form, storing enough energy to survive winter and the first few stages of life in spring. By definition, according to the University of Illinois Urbana-Champain, bulbs are categorized as “any plant that stores its complete life cycle in an underground storage structure.” Winter-hardy species that bloom in spring, like tulips and daffodils, have evolved to survive in the ground all season on stored carbohydrates.
Tubers, while also underground stems, contain nodes (or “eyes” in potatoes) that can appear anywhere, giving the tuber the ability to grow in any direction. Crops like potatoes, sweet potatoes, yams, and anemones are tubers.
Dahlias are tuberous roots, meaning they have one large, centralized stem from which thick roots grow. These can be easily split in spring, giving you more tubers to plant each year.
For ease of discussion, I’ll refer to all of these as bulbs in this article because they can all be stored in similar ways.
Container Bulb Storage
Lots of different containers will work for bulb storage. Here are some acceptable options.
Opt for a readily available, breathable cardboard box with side holes for ventilation.
A simple, breathable cardboard box from your local shipping store or grocery store is a great option because they’re easily accessible and usually free. One with holes in the sides will provide the necessary ventilation.
Many growers place tubers into plastic bags before placing them into cardboard boxes, but it’s a personal preference. Since any soil present on the tubers when you put them into storage will fall off, the plastic bags will prevent a messy cleanup come spring.
Also, since cardboard boxes will eventually break down, be sure the bottoms are nice and sturdy before choosing them for your storage container. If you notice any wet or weak areas, it may be time to retire the box.
Sturdy wooden nesting boxes are an excellent choice for bulb storage.
Go to any craft store, and you’ll find sturdy wooden boxes. If they nest inside one another and easily stack, this is a great option for bulb storage.
Pro tip: If storing in a garage, stack a few cinder blocks on the ground and stack the wooden boxes or crates on top of them. This will keep them just a bit warmer and decrease the chances of unwanted moisture seeping in through the concrete. They also lift the bulbs away from any curious mice.
Use old milk crates or storage tubs for bulbs.
If you have old milk crates or storage tubs, these will work. Plus, they stack! Just line them with newspaper. Cinder blocks underneath the crates are recommended.
Reuse plastic bags from under your sink for an easy storage solution.
If you’re like me, you have a plastic bag full of other plastic bags under your kitchen sink. Grab a handful of those and use them as storage containers.
Many growers will advise you to leave soil on your bulbs and allow them to dry for a few days before storage. Soil left on may provide added protection and moisture during the long months ahead.
Don’t overpack your bags, and loosely tie them so air can flow freely. Then, place them into a box or crate or just onto a shelving unit.
Paper bags are a suitable alternative for overwintering bulbs, but they break down faster.
About as easily accessible as plastic bags, paper bags can be similarly used for bulb storage. Just keep in mind these will break down much faster, so allow proper time to cure before adding them to paper bags, as any excessive moisture will just cause the bag to break down and potentially lead to rot.
Here are a few unconventional but great options for bulb storage.
An Old Refrigerator
Repurpose an old, non-functional refrigerator to provide critter protection, height, and darkness.
If you have an old refrigerator that’s out of order, repurpose it into bulb storage before simply discarding it. This container option is already tall, dark, and safe from critters. One grower suggests keeping a large bowl or bucket of ice in the bottom for added humidity and coolness.
A Walk-In Cooler
If you have a walk-in cooler used for produce and flower storage, it also makes a great storage spot during the off-season.
If you grow and store fruits, vegetables, and flowers, you may have a walk-in cooler for fresh produce and flower refrigeration. This can be used similarly during the off-season for bulb storage. It’s already dark, dry, and safe from critters, so why not utilize it over the winter?
Remember that you’ll have to keep the temperature constant and humidity levels at around 90% for proper bulb storage.
Add Packing Medium
Include moisture-wicking materials like vermiculite, animal bedding, newspaper, or wood chips to remove moisture.
No matter what container you choose for storage, add some sort of wicking material to help wick moisture away and prevent rot.
A few options are coarse vermiculite, animal bedding, newspaper, and wood chips. Try more than one to see what works best in your area.
Where to Store
Select a suitable location for storage, ensuring it is cool, dark, and dry.
After packing up your containers, pick an area conducive to healthy bulb storage.
Here are a few important characteristics that must be true about the chosen storage area:
- Consistent temperatures between 40-45°. Warmer temperatures will encourage fungi or make bulbs think it’s time to wake up, forming sprouts and roots too early.
- A container that retains moisture but is not airtight.
- Somewhere that receives proper ventilation and airflow.
- Away from critters and pests.
- Off the ground.
Areas of your home that may work include:
- A sealed-up attic
- An unheated, insulated garage
- Dark, dry closet
- Utility room
- Root cellar
Pro tip: You may think you’ll remember which bag contained which dahlia variety or how many of a certain type of daffodil you put into storage, but you probably won’t. Label your containers with names and amounts for future reference. You can use zip ties, colored tape, or tree tags. Your spring self will thank you!
To Store or Not to Store?
Avoid storage areas with moisture, direct sunlight, excessive dryness, and temperatures below 35°F.
Here are a few examples of where not to store them in case you’re on the fence about certain areas. AVOID:
- Anywhere there is moisture present. This may cause mold and rot, which will destroy bulb viability.
- A location with direct sunlight.
- Anywhere overly dry. Your packing medium should allow for ventilation but also retain some of the moisture so they don’t shrivel up.
- A place that could allow temperatures to go below 35°. This will likely kill tubers. Avoid storing them in locations above 55-60° to prevent early sprouting.
- In tied-up bags or airtight containers. This can cause humidity levels to rise, or the opposite, dry the contents entirely. The result all depends on your region and storage setup.
Inspect Throughout The Winter
If you see a bulb with mold or rot, remove it to prevent spreading.
You should check in throughout the winter months to verify all bulbs remain healthy. If they feel a little dry, lightly spritz them with clean water.
If you notice any mold or rot, remove the bulb immediately to avoid it spreading to others. Bulbs release ethylene when rotting, a gas that encourages sprouting, so others will soon be affected if the rotting bulb is not removed.
Studies show that even some exposure to this gas can cause serious damage like stunted growth, abnormalities, or future bulb splitting.
Also, be on the lookout for any pest and critter damage and adjust your setup as needed.
Frequently Asked Questions
The tubers are not likely viable at this point. If you squeeze the tuber and there seems to be no moisture left inside, it has perished. If you’re unsure, you could pot them up with some fresh soil, place them in a warm place, and water them lightly. If they begin to sprout, you can transplant them into the ground.
As long as your garage remains above freezing and is unheated and insulated, they should be perfectly fine here. The bulbs should not be too cold nor too warm. Keep them off the ground, maintain aeration, and ensure ventilation.
Yes! Bulbs are yummy winter treats for mice. They offer a plethora of carbohydrates that they’re looking for through the winter months. Set traps nearby, plug in ultrasonic pest deterrents, or add mothballs to your storage containers to help decrease pest damage.
It’s that time of year when gardens are being cleaned up, tools are being cleaned and sharpened, and plans are made for winter bulb and tuber storage. If you’re unsure where to store bulbs, seek a dry area that remains above freezing and is safe from critters. Select from the many creative container options and follow guidelines for safe bulb and tuber storage.