Digging, Dividing and Winter Storage Of Dahlia Bulbs

You may be one of those fortunate souls who has stored their Dahlia bulbs year after year with minor loss. Unfortunately, however, many roots are lost each winter by rot and excessive shriveling followed by decay.

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Driving along the country roads in the fall, where the open places reveal the dahlia plants, many of these tell a story. In many gardens, the flowers are:

  • All the same color.
  • The same variety.
  • The sole survivor of possibly a dozen or so types the gardener started a few years back.

All gone except this one, whose hardy roots could be thrown in almost any out-of-the-way basement corner in the fall and come up sprouting in the spring.

Years ago, a wholesale grower packaging thousands of roots for the retail trade, queried as to what storage method he recommended, sent me a printed copy of his cultural instructions and attached a short note.

It read as follows…

“You will notice I do not include anything on storage. This is because the loss of roots makes business good.”

Candid, anyway.

With equal candor, my correspondent might have written, “It is so hard to set down a standard method which will work successfully in all parts of the country and under the varying facilities of individual growers, we simply do not attempt it.”

In California, during the dormant period, roots may be stored on the ground in any sheltered spot. In Minnesota, with its short growing season and cold winter, the problems are different.

Plants Should Mature

There are, however, some hints we can offer for storing Dahlia tubers. The start toward successful storage is made the preceding spring in the garden. Tubers to store properly must be well matured, so plant as early and grow as late as weather permits.

In regions where frost is a fall visitor, digging customarily awaits the event. Without delay, cut the stalks cut off within a couple of inches of the ground. A pair of long-handled lopping shears are ideal for this purpose.

If stalks are allowed to stand, a liquid made up of sap and decayed plant tissue runs down the inside of the stalk to the root crown, which is often a source of rot. It is beneficial for the storage ahead to leave the clumps in the ground for a week or so after cutting off the stalks.

When lifting the clumps, make a second cutting, this time cutting off the stalk stump to within one or two inches of the crown. If the diameter is one and one-half inches or more, split it in two.

Related: Questions on Growing Dahlia Bulbs

Leaving The Ground, Dirt, Or Soil

If your soil is such that it adheres to the clump, leaving it on is one of the best ways to assure good storage. After digging, allow the clumps to dry out for several days on the garage floor.

This is referred to as a “curing” process. The length of time of this curing depends on the condition of the ground at digging time. If wet from rains, a longer time is needed. Do not divide the clumps in the fall. Wait until spring.

Packing or Storage Medium

Various packing and storage mediums, such as sand, vermiculite, peat moss, sawdust, and wood shavings, are used to reduce evaporation and consequent drying out of the roots. Of these, vermiculite has proven to be satisfactory.

Some Dahlia growers leave the soil on. Others wash the excess dirt off the clumps using a garden hose or a tub of water.

For those storing roots for the first time and wanting to play it safe, it might be advisable to try one of these on the major part of their roots. We suggest trying one of the methods mentioned below, which omits any packing material for the remainder.

When the soil is left on the clump or a packing medium added, this means a dirty floor both fall and spring. Besides, it increases the work of packing and unpacking.

A significant majority of the commercial growers and the fanciers use nothing of this kind.

If you are lucky enough to have a cold or unheated basement, store the clumps uncovered, in empty pots or cardboard boxes placed on the ground. However, if it happens to be a fruit storage compartment with a cement floor, a bucket or tray of water should provide the necessary humidity.

Or you can keep the floor wet. If neither is available, store it on the floor in the coolest part of your basement. Note we say “on the floor,” for this is where the humidity is the highest. For this purpose, pots or cardboard boxes are lined and covered with several thicknesses of newspaper.

Key Is Humidity

Store Dahlia roots in temperatures ranging from just above freezing up to 70° degrees Fahrenheit. While there has always been a leaning toward the lower temperatures in the past, recent experiments point to the higher temperature for more dependable results.

The trick is to provide just the right amount of humidity. An overdose of this at a low temperature will cause more damage than at a high temperature.

Thirty days after storing, take a peek to see how they are doing. If you notice any mold or rot, increase the air circulation. If a shriveling on some of the roots are detected, add a little moisture and make sure the covering is reasonably air-tight.

Chances are they will need no further attention to the balance of the winter. Remember, no storage method works 100 percent. Expect to have a few losses among the “poor keepers.”

It is well for this reason if for no other, to keep a variety of identification tags on your roots so that you can identify any lost. One of these might be your favorite which you would want to replace.

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Fall Dahlia Care

When fall comes, and the frost has killed the leaves, it is time to think about digging the dahlia tubers. Within a week after killing frost, cut the tops to the ground. Then allow the stalks to bleed for at least a week before digging.

Now you are ready for the real operation. Take a spade, garden fork, or shovel, whichever you are the handiest with, and pry up the plant carefully from all sides.

Next, lift the Dahlia clumps carefully and cut the stalks about two inches above the crown. Let the dahlia tubers dry in the sun and air for about a day. A little soil may stick to the clumps, but that is easily removed by tapping the end of the cut stalk with a trowel, block of wood, or any heavy object.

Some varieties are poor winter keepers, others good, but there is no need to segregate the two kinds with good care. However, if a tuber should break off, the wound should be dusted thoroughly with sulfur to keep out rot.

If any tuber is injured, remove the damaged portion with a clean, sharp cut and sulfur applied.

When it comes to the actual storage, line the storage container with paper, preferably waterproof. Then put in a layer of tubers taking care to keep them from touching, cover with vermiculite, almost-dry peat moss, or sawdust, put in another layer of tubers, and cover completely. Finally, split the largest clumps to facilitate packing.

by JR Berry

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