Harvesting - Preparing - Storing - Planting - Requirements

In this topic, we are using the term "bulb" the way the general public uses it. The common definition of the term includes true bulbs, corms, tuber, tuberous roots, rhizomes and other structures. These structures we will call bulbs are all meant to be perennials. That is, their life cycle should be more than two years in their native environments. They have developed the ability to go dormant for periods of the year in order to survive either cold temperatures or dry conditions.

In temperate regions where frost is part of the yearly cycle, many types of bulbs are perfectly hardy including tulips, daffodils, lilies, fritillaries, muscari and many others. However, many bulb species have been imported into this part of the world from tropical and subtropical zones. These plants, although perennial at home, must be protected from the cold if we expect to get multiple years of beauty from them.

We call these plants tender bulbs and they include cannas, dahlias, gladiolus, tuberous begonias, calla lily, caladium, freesia, tuberose and others. The choice is to treat these plants as "annuals" and replace them every year or figure out how to store them so that they survive the winter.

Although these plants represent a large variety of types, there are certain factors that are consistent for all:

Harvesting the Bulbs
  • One common trait of all of these plants is that they will die back to the ground when exposed to frost temperatures in fall. Some foliage will die with a hint of frost while others will survive into the high 20 degree range but they all will lose their foliage.

  • At that point, it is time to dig the bulbs from the ground. This should be done carefully to prevent damage to the bulb which can lead to rots. A spading fork is well adapted to this process. Start digging several inches away from the bulb to avoid damage.

  • When the plants are out of the ground, gently knock off any loose soil and cut the foliage down to within an inch of the bulb. Discard any wounded, diseased or damaged bulbs.

  • Next, allow the bulbs to dry off and "cure". This may be leaving them on a picnic table in the sun for a day or in a dry, location in the shade. Do not allow them to dry excessively but they should not be wet when put into storage.

  • Gently brush off any remaining soil. Do not wash them in water at this point in the process. Some people recommend dusting them with a powdered fungicide.

Preparing for Storage
  • Store only healthy bulbs. Discard any that have wounds, signs of disease or insect damage or mechanical damage from digging.

  • The key to storage is to keep the plant material cool enough so it does not grow or rot and warm enough so it does not freeze. It also must be moist enough so that the bulbs do not dry out but dry enough to that they do not rot.

  • Use clean shallow trays, plastic containers or sturdy cardboard boxes.

  • Put a layer of dry sand, dry sawdust, peat moss, perlite or vermiculite in the bottom of the container.

  • Lay the bulbs on the surface of this layer and be sure that one bulb is not touching another to prevent the spread of rot from one plant to another.

  • Cover the bulbs with another layer of the material.

  • Repeat the process alternation layers until the container is filled.

  • Label each layer if the bulbs are a different variety or species and label the container too.

Storing the Bulbs.
  • A temperature of between 40 and 50 degrees F is usually considered ideal for storing bulbs.

  • If you have a small volume of bulbs, you might use an old refrigerator in the garage or basement.

  • A root cellar would be the best but few of us have them now.

  • An unheated 3 season type porch will do in most years.

  • An unheated but attached garage will often suffice.

  • Periodically open the containers and check the bulbs. If there is any sign of rot, remove the infected bulbs and make sure the media is dry before returning to storage.

Planting Tender Bulbs, Corms, Tubers and Roots
  • These bulbs are not only tender in the fall but they are also sensitive to cold in the early spring. To get a jump on the season, many of these bulbs may be started indoors under fluorescent lights or in a bright window to get a jump on the season.

Storage Requirements of Common Tender Bulbs
Name Structure ░F. Storage Digging
Achimenes rhizomes 45-50 Store cool and dry. Dig when leaves turn yellow and let dry after digging.
Acidanthera corm 35-40 Store the same as gladiolus. Dig 6-8 weeks after bloom
Anemone or Windflower
(A. Coronaria)
tuber 40-45 Store like dahlias. Frequently sold as an autumn- planted bulb, but not winter-hardy in Minnesota.
Tuberous begonia
(B. Tuberhybida)
tuberous roots 50-55 Remove foliage and store in sphagnum peal or vermiculite. Dig when foliage turns yellow and cure with
Caladium tuber 50-55 Cure with remaining foliage
and store in sphagnum peat or vermiculite.
Dig when foliage turns yellow or after frost has killed foliage.
Calla Lily (Zantedeschia) rhizomes 50-56 Store in sphagnum peat
or vermiculite.
Dig when foliage turns yellow or when foliage is damaged by frost
Canna tuberous roots 40-50 Store in sphagnum peat, vermiculite or sand. Dig after frost has damaged foliage and allow foliage to dry a few days before digging. Dig carefully to avoid damage which will cause rotting.
Dahlia tuberous roots 40-50 Cure carefully to avoid desiccation. Pack roots in vermiculite or sphagnum peat. One recommended technique is to place the roots in plastic bags with small perforations and enclose an equal volume of vermiculite or peat to absorb the moisture which is given off by the roots. Dig after frost has killed foliage or damaged foliage. Dig carefully to avoid damage.
Freesia corm 35-40 Store the same as gladiolus.  
Gladiolus corm 35-40 Store in labeled paper bags. Dig 6 to 8 weeks after bloom or when frost kills
foliage. Cure 2-3 weeks, then remove old corm and cormels. Cure in a dry, well-ventilated area at about 60░-7O░F.
Gloriosa Lily
(Gloriosa superba)
tuberous roots 40-50 May be stored in the pot or dig the tuberous roots and store like dahlias. May be started indoors again after 2 months storage.  
bulb 60-65   Should be dug before frost. Avoid breaking the heavy roots attached to the bulb.
Blazing Star (Tritonia) corm 35-40 Store the same as gladiolus. Do not break corm cluster apart until spring. Dig before freezing.
Oxalis bulb 35-40 Store in paper bags or in vermiculite. Dig after tops freeze
Tigridia corm 35-40 Cure and store like gladiolus. Dig 6-8 weeks after bloom or after frost.
Tuberose (Polianthes) tuber 55-65 Store in plastic bags with sand or vermiculite. Dig after tops die or are killed by frost

Note: We have provided some general information and observations on this topic aimed at the home gardener. Before you take any serious action in your landscape, check with your state's land grant university's Cooperative Extension Service for the most current, appropriate, localized recommendations.

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