Preparing Seedlings for Planting

Late Spring Planting (acclimatization)

As the planting season progresses and the days become warmer, acclimatize seedlings coming out of cold storage before planting. Wrap seedlings a day before planting and keep them in a shaded area, such as the wrapping shed, where temperatures are above 40 degrees Fahrenheit, preferably 50 to 60 degrees Fahrenheit. Plant trees the following day.

Acclimatization is generally done at the storage unit and not at field sites. Place seedlings upright in boxes or tubs with their tops exposed to air. Wrapped bundles must be kept moist. Several methods can be used, such as placing upright bundles in 1 or 2 inches of water to maintain the wicking action and keep the wrapping wet. Another method is to wet bundles with a hose periodically. This provides moisture that keeps the tree-wrapping fabric or burlap wet.

Seedlings planted without acclimatization on days with temperatures higher than 75 degrees Fahrenheit may suffer from shock, because water in the tree crowns will be lost rapidly. Seedlings that have just thawed cannot replace water rapidly because their water transport functions are not yet fully active.

The effect is similar to physiological drought plants can experience during winter when crown temperatures are warmed to the point that moisture demands cannot be met by physiologically inactive roots and stems.

To avoid problems:

• Make sure that frozen seedlings are thawed completely before preparing them for planting. Never attempt to separate seedlings’ roots while they are frozen.
  
  
• Do not allow the temperatures inside a sealed tree package to rise above 36 degrees Fahrenheit for any appreciable time.
  
  
• When wrapping seedlings, if they become warmer than 40 degrees Fahrenheit do not put them back in boxes and seal or roll the bag closed. Once seedlings have been wrapped and warmed, keep their tops upright and exposed to fresh air.
  
  
• Do not acclimatize seedlings before planting if subfreezing weather is forecast. Trees full of moisture can be damaged when temperatures drop below the mid-20s. Consider suspending planting if severe cold weather is expected.