Temperature of Delivered Seedlings

Check seedling temperature as soon as seedlings arrive. Normally, bareroot stock should arrive unfrozen although it can be shipped frozen. If unfrozen, the air temperature should be between 32 and 38 °F. The temperatures inside the tree box should not exceed 36 °F. Container stock should arrive unfrozen. Ideally, the temperature should be about 35 °F with temperatures inside the box no higher than 36 °F. If the stock is shipped frozen, the temperature inside the tree box should be between 28 and 32 °F.

Delivery Temperature of Bareroot Stock

Most bareroot stock is delivered in the spring. The stock may come unfrozen or frozen.

Unfrozen Stock

When unfrozen stock is delivered, the temperature inside the tree box should not exceed 36 °F nor should the temperature have exceeded 36 °F at any time during shipment. If the trees get warmer than 36 °F, they will begin respiring inside the boxes, increasing the temperature. Increased temperature will further stimulate activity in the trees and in any microbes in the boxes. Once these processes start, they may increase at an exponential rate and be difficult to stop. Lodgepole pine is very sensitive to increased respiration at low temperatures. If the temperature is higher than 36 °F when the stock is delivered, set your district coolers to draw down the temperatures to below 36 °F immediately and get the stock to 32 to 34 °F within a couple of days.

Frozen Stock

For frozen stock, the temperature inside the tree box should be between 28 and 32 °F. Temperatures inside the truck compartment should not be below the mid-20's. Lower temperatures might damage the trees. The temperature of the boxes of trees next to the refrigeration unit should be checked, especially if cold air from the unit has been blowing directly on them. If you order frozen trees, the trees should be frozen when they arrive. If they are only beginning to thaw, no harm has been done. They can be refrozen in the district cooler. If the trees have thawed and warmed to over 36 °F, freezing may cause problems. Notify the nursery immediately that the stock has warmed. In such cases, it is best to handle the stock as thawed or unfrozen.