How to Store Bulbs for the Winter

The word “bulb” is commonly used to refer to geophytes, which are a group of plants with “underground storage organs.” There are five basic geophytes: true bulbs, corms, rhizomes, tubers, and tuberous roots. For the purpose of this article, we will focus on the more common bulb, corm, and tuber.

Bulbs, corms, and tubers are quite different than traditional seeds, and therefore must be stored and handled differently. A seed is the embryo of a plant, whereas a bulb, corm, or tuber is actually a mature plant structure. Seeds can be annuals, biennials or perennials, whereas bulbs, corms, or tubers are only perennials.

Examples of Common Geophytes

Here's a helpful guide for learning the difference between the different types of geophytes:

True Bulbs

True bulbs can be classified into two major categories based upon their covering. Tunicate bulbs have a dry, paper-like outer covering, whereas nontunicate bulbs have a scale-like covering and are fragile while being stored or handled. True bulbs frequently create smaller offset bulbs, which can be separated into more plants. The most common types of true bulbs include daffodils, lilies, onions, and tulips.

Onions are some of the most common true bulbs.

Corms

Corms look similar to bulbs but have a fattened and flattened base of the stem. Unlike bulbs that produce offset bulbs, corms produce cormels beside the plant. Common types of corms include crocus and gladiolus.

Rhizomes

Rhizomes tend to grow horizontally right below the surface of the soil. Because of their unusual shape, the plant has multiple growing points and can be easily propagated by cutting it into sections. Common types of rhizomes include the calla lily and the lily of the valley.

Tubers

Tubers are a unique type of plant that doesn’t fit into any traditional category. They are characterized as underground growing stems that can be propagated by cutting the tuber into sections and commonly have “eyes” that will sprout to plants that grow at the surface of the soil. Common varieties of tubers include caladium, water lilies, and the unusual potato.

Tuberous Roots

Unlike tubers, tuberous roots don’t have “eyes,” but they tend to sprout at one end and grow in clumps. Propagating tuberous roots is much more difficult, as you must have sufficient crown tissue in order to get a successful plant. Common examples of tuberous roots include dahlias, sweet potatoes, and tuberous begonias.

Why Store Geophytes?

Some gardeners treat bulbs, corms, and tubers as annuals, and leave them in the ground all year long. The problem with this philosophy is that it is a waste of money to buy new bulbs each year.

Why not take a little time and effort and save some of that cash on something else for your garden instead? Storing your bulbs, corms, or tubers is the economical choice. You may even find that older bulbs produce larger plants with each passing season.

When to Store Geophytes

Remove bulbs, corms, or tubers from the soil before frost occurs in your area. If the bulb, corm, or tuber is exposed to harsh conditions, it could cause rot and the plant could die.

How to Store Geophytes

Here are some helpful tips on how to store certain types of geophytes:

Bulbs

1. Remove the bulbs from the soil carefully, making sure not to damage the bulb.
2. Brush off excess soil.
3. Set bulb aside for a few days in a shady area to dry.
4. Dust bulbs with a fungicide to prevent rotting during storage.
5. Set bulbs aside in a vermiculite or peat moss-filled box, ensuring bulbs aren’t touching one another.
6. Store in a cool location, preferably 40 to 55 degrees Fahrenheit.
7. Inspect bulbs throughout the winter to add moisture to the packing material and to look for mildew. Gently scrape off any mildew that may be occurring and dust bulb with sulfur.

Corms

1. Trim foliage down to about 2 inches above the corm prior to the first frost of the season.
2. Remove the corm from the soil carefully.
3. Brush off excess soil.
4. Set the corm aside for several weeks in a dry location with good airflow. Allow the corm to dry out.
5. Remove remaining shriveled foliage with sterilized clippers or by twisting off by hand.
6. Store the corm in an onion bag or a nylon stocking in a cool location, preferably 35 to 45 degrees Fahrenheit.

Tubers

1. Trim foliage down to about 2 to 4 inches above the tuber after the first frost of the season.
2. Check plant-specific instructions for how to store your particular tuber. For example, tubers like dahlias should be dried out for a few weeks, then packed in peat moss or wood shavings and stored between 35 to 45 degrees Fahrenheit, whereas lily rhizomes may just be left in an open shallow box and stored at 45 to 50 degrees Fahrenheit.

Label Your Geophytes Before Storage

Always label bulbs, corms, and tubers prior to storage. It is easy to forget what you stored and where you stored it a few months ago. Labeling the bulb, corm, or tuber with a name and even the color of the bloom, so you know what to plant where.

Inspecting Geophytes After Storage

Some slight shriveling of geophytes is to be expected, as moisture has evaporated from the young plant. Excessive shriveling, however, may indicate a problem. Toss any geophytes that you suspect have shriveled too much.

Inspect geophytes for rot. Don’t ever try planting a bulb, corm, or tuber that is mushy or has mold on it.

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© 2018 Diane Lockridge