Storing and saving tender plant bulbs during winter

It’s not too late to plan for next year’s garden party. Now’s the time to dig up tender, summer-flowering bulbs, tubers, rhizomes and corms and store them for winter.

Colocasia, also known as Elephant Ear, bulb. Photo: Patrick Voyle.
Colocasia, also known as Elephant Ear, bulb. Photo: Patrick Voyle.

Many gardeners add exciting, new plants to their gardens each year. Some of these may be “tender” plants, meaning that a dose of Michigan winter will squeeze the life out of them. Since tender plants are not hardy to Michigan’s winters, they freeze and die. However, smart gardeners know they can dig and save those exotic cuties to come again next summer. All that is required is a bit of planning and work.

Some examples of tender plants are Tuberous Begonia, Canna, Colocasia or Elephant Ear, Caladium, Dahlia, Calla Lily, Gladiola, Tuberose and Freesia. Some others like Four O’Clocks and Oxalis may not be familiar to gardeners that store bulbs, but these can be kept the same way. For sake of brevity, all underground roots are going to be called bulbs in this article.

Michigan State University Extension offers these 10 easy steps for saving tender bulbs.

  1. Wait for the first heavy frost or killing frost. The tops should look sad, wilted and browned. Try to dig on a warm day above 50 degrees so cold does not negatively affect your plant bottoms. Bulbs must be dug before the ground freezes.
  2. Cut the stems off a distance above the soil level. Depending on the size of the plant, it might be 1-2 inches, or up to 4 inches. This can make digging easier. For bigger plants, the shortened stem serves as the handle to lift and move the bottom.
  3. Carefully dig up the root structure. It is very important not to cut, nick or scrape the bulb. If in doubt about what lies below, use your fingers to dig to find the size of what you are digging. Plants with round structures like bulbs and corms are easier because they are symmetrical. Use the pads of your fingers or wear gardening gloves so you do not claw or scratch the exterior. No damage means there is a better chance of no rots in the bulb.
  4. Gently remove the excess soil. It is not necessary to wash the root structures because you want them to dry as rapidly as possible. Check for shriveled or dead material or parts that are soft or oozing. The damaged material will not make it through the winter and could cause the good ones to decay. Sort and pitch, if necessary.
  5. Place into a container to bring indoors. Do not layer too many on top of each other. This is another way they can become bruised or scuffed. If the temperature outdoors is below 50 degrees, bring your sunken treasures indoors rapidly after digging. None of these should spend much time outdoors or in a cold garage.
  6. Bring into a heated building where the temperature is above 65 degrees to begin the drying process. Damp material that is stored can rot. This is very much like “curing” potatoes. The skin on the outside has to dry and toughen up for the long winter’s sleep. The process could take two weeks or more, depending on the size of the bulb. Turn the bulbs periodically to facilitate drying on all sides.
  7. Stems should not be cut flush with the top of the bulb or rhizome. This allows rots to enter the bulb. In two weeks or when you think that the bulbs are dry, shorten the stems and check the inside of the stem to see that it is dry. If it is, it is ready to store.
  8. If labeling is important, you can put a sticker on the stem handle or use a marker and put information directly on the bulb. Pack similar bulbs together. You might label the outside of the container if there are many stored or multiple containers.
  9. Use a container that is sturdy and will handle the weight of your plant material. It could be a strong cardboard box or a paper grocery bag. Use packing material around the bulbs. It could be wood shavings, sphagnum peat or Canadian peat, or many other things. These materials cushion the contents, but the peat mosses help to prevent decay because they are acidic. The packing material cushions the bulbs and if one decays, it is not lying on and ruining another bulb.
  10. Store the packed box or bag in an area where the temperature will remain between 40 and 50 degrees all winter and the container is not in sunlight. You want safe and restful sleep for next year’s flower explosion.

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