Flower bulbs are unique in the world of seeds, roots, and rhizomes. Although we sometimes group them with rhizomes, they are slightly different but have similar needs. Some grow best after a period of cool weather, while others can’t tolerate cold weather at all.
Many gardeners don’t have the ideal climate conditions for their bulbs to thrive. To mitigate this, they must find a storage method in the off-season. Most bulbs and rhizomes can be stored for a while, and if given the right environment and care, they can last longer than you might think. However, they might not make it through the season if stored incorrectly. Planting practices will also factor in your success.
As in all areas related to plant care, there is a balance to be reached in attempting to replicate the conditions under which they prefer to grow. If this balance is disrupted, sometimes even a small amount, you could end up with rotten bulbs, dried-out bulbs, or ones suffering from temperature damage.
How long can you store them? That question has some very important variables to consider, including the storage method you choose.
The Short Answer
Most bulbs can be stored for about one year, although they tend to perform better if stored for six months or less. Cold-hardy bulbs are best stored in the refrigerator, while frost-tender bulbs should be stored in a cool, dry place at around 60°F.
The Long Answer
One year or less of storage is best.
In general, when we talk about bulbs, there are two different types: those that are cold-tender and those that are cold-hardy. For our discussion, we will consider rhizomes to be in the same class because they are typically stored similarly and have a similar shelf-life.
The longest recommended time for storage is a maximum of one year. Beyond this, you may get some healthy bulbs, but your germination rate will be significantly reduced. Your success rate will be markedly better if you store them for six months or less.
Cold-hardy Types
Cold-hardy bulbs require cold storage and stratification for successful growth.
In general, cold-hardy means they can withstand freezing weather and are easier to store. This is partly because they prefer to be stored with some moisture and in cooler temperatures, where a fungus is less likely to grow. However, mold can be an issue.
Cold-hardy bulbs usually require a period of cold stratification. That means that they need to be brought to a certain temperature for a certain amount of time to indicate that it is time to break dormancy and produce foliage and flowers. Without this cold period, they may not know that it is time to wake up, and your success rate will be lackluster.
Some of the common cold-hardy options are tulips, daffodils, irises, crocus, and bluebells. These plants are native to areas with a significant period of cold weather and usually a hard freeze. A hard freeze is when the temperature is cold enough to freeze the soil to a certain depth.
Acknowledging their native environment makes it easy to understand what they need in terms of storage and how you can make them grow, even in warmer climates in many cases. If a bulb enters a dormant state due to falling temperatures, and you can’t achieve that by planting it outdoors, you must imitate it artificially.
If you live in a cool enough climate, fall is the time to put these cold-hardy bulbs in the ground. Plant before the ground freezes; this way, they will naturally get the temperature fluctuations needed to become beautiful plants in the spring. If you live in a warmer climate, there are things you can do to force them to grow.
How to Store Them
Store in a clean, breathable container at 40°F.
Any cold-hardy bulbs you plan to store should ideally be stored around 40°F or lower. This is about the average temperature at which most folks keep their refrigerator. They also typically need moisture during storage, and the moisture level in the fridge is good for them.
Dormant bulbs are still living, and while they may not need the same amount of moisture they will get in spring, they need to maintain a certain moisture level within themselves. When plants are dormant, they naturally need less water than during the growth period, when they rapidly produce foliage and flowers.
Providing the cold they need artificially, or cold stratification, is a simple process. Place them in the refrigerator, and ensure they are nice and clean before packing them away. Allow your bulbs to dry before storing them to help avoid mold.
Breathable mesh bags work well, too. The moisture level in the refrigerator should be sufficient to keep them hydrated. Inspect monthly, and if they appear dried out, you can place them in a container with lightly dampened peat moss or perlite.
Keep your bulbs away from fruit in the fridge. Fruits release ethylene gas, which inhibits future blooming.
Cold-tender Types
These frost-tender bulbs require winter storage in many climates.
Cold-tender types include plants like ginger, dahlias, canna lilies, and gladiolus. They naturally grow in warm climates, and they cannot survive below a certain temperature.
If you want to grow these plants in a climate that experiences cold weather, especially a hard freeze, you must dig them up and store them in a space that doesn’t freeze during the colder months.
In contrast to those that require cold stratification, they prefer warmer, dry locations. Ideally, a moderately cool, dark space is ideal.
How to Store
Properly clean and cure bulbs before storage to prevent rot.
After digging up your frost-tender bulbs, it is important to clean them thoroughly. When given the right environment to reproduce, soil can contain pathogens that can land you with a mess of rotten bulbs. Likewise, allowing these bulbs to dry out is important before storing them.
The process of drying for storage, called curing, varies between types. Some may only need a few days; others require several weeks to cure properly. For dahlias, look for skin that’s just beginning to wrinkle but isn’t dehydrated.
Cure gladiolus, amaryllis, and canna lilies for a week or more to be safe for storage. An ideal way to cure is on a screen so air can circulate around them completely. Place them in a cool, dry room during this time.
After curing, choose your storage method. I highly recommend surrounding them with peat moss or perlite to help with moisture regulation. You can fill nylon bags with the medium and bury your bulbs in these, ensuring they don’t touch.
Another method, and one that I prefer, is storing in shallow cardboard boxes. They are then easy to access and label. Fill the box with peat moss or perlite and bury the individual bulbs so they are not touching.
A Note for All Types of Bulbs
Regularly check for moisture and remove any bulbs with signs of damage.
If you store bulbs for more than a month or two, it is important to check on them regularly. Your main objective in this is to determine whether or not the moisture level is at an ideal level. Dispose of any that show signs of damage. It’s not a terrible idea to refresh the potting medium with fresh medium to prevent the spread of any fungal pathogens that may be starting to appear.
Look for those that have dried out too much, are crumbling, or are hollow inside. Remove them and inspect their neighbors to make sure that they, too, are not drying out. If your bulbs are too dry, you can mist the potting medium with a bit of water before placing them back in storage. This will typically be less of an issue in fridge storage.
Final Thoughts
Whether you intend to store your bulbs only for a season or need to keep them in storage for a longer period, following these best practices will assist in keeping them healthy and alive. Storing bulbs correctly and checking in to ensure they are still healthy is the best way to prolong the life of your bulbs.
