Other Types of Coolers

All types of refrigerated coolers have been used to store trees. Milk or beer coolers, meat coolers, fruit storage facilities, and refrigerated semi trucks have all been used. Any unit that serves as a tree storage facility over the long-term must be adjusted so that the temperature during defrosting is at an absolute minimum and the relative humidity is kept high (95 percent or higher). Temperature fluctuations cause trees to break dormancy and allow moisture to condense, both of which stimulate the development of microorganisms. The increase in biological activity increases heat and toxic gases in the tree boxes, which may spoil the trees.

It is not easy to adjust most coolers for long-term tree storage. The required combination of short defrost cycles and high humidity is difficult to provide. Fruit storage coolers are an exception. However, if you use fruit storage facilities, the trees must be kept separate from the fruit and any respiration retardants that might be used to preserve the fruit. These chemicals have been known to kill trees in short order.

If you have to use refrigeration equipment that is not designed specifically for tree storage, keep the storage time to a minimum. Keep the temperatures as close to 34 °F as possible and avoid temperature fluctuation as much as you can. You should not need to worry about humidity during short-term storage if the trees are properly packaged. Container stock is more adaptable than bareroot stock, but it is best to keep storage time to 2 weeks or less. Leave the stock at the nursery until you are ready to plant. Use several small shipments rather than one large shipment. Don't forget that it is critical to leave air space between boxes of trees that are in storage.