JARS v58n4 - Tips for Beginners: Warehousing First Year Seedlings Over Winter

Tips for Beginners: Warehousing First Year Seedlings Over Winter
Dr. Mark G. Konrad
Sewickley, Pennsylvania

One of the most difficult and important aspects of a successful seedling program is the overwintering of new plants the first year. With inadequate or poor preparation the losses can be great and, in the worst-case scenario, the entire work of the year can be wiped out.
To overwinter the first year seedlings successfully special attention must be given because of their juvenile tenderness compared to the hardiness acquired with aging.
To help overwinter small seedling plants various techniques have evolved over the years including unheated greenhouses, polyhouses, coldframes and planting outdoors with environmental protection.
All of these strategies are fraught with a certain amount of hazard such as overheating, freezing and thawing resulting in plant upheaval. As well there is often destruction from small animal invasion. Inclement weather bringing wind and snow damage can also wreak havoc. Unfortunately, I have been a victim of many of these extremes.
In the last few years I have had the most success by warehousing potted seedlings in an unheated but insulated garage.

Warehoused potted seedlings in the 
author's garage
Warehoused potted seedlings in the author's garage.
Photo by Mark G. Konrad

David Leach brought attention to this method in his book Rhododendrons of the World . He concluded that dormant rhododendrons do not require light or ventilation. An unheated outdoor shed was designed and used by him to overwinter seedlings successfully. The flats with seedlings became frozen over the winter months, but they were allowed to remain that way until thawing took place in the spring. His success has been a testimony to the method.
As a bonus, this method eliminates a great deal of labor and expense and allows time for winter vacations.

Leach, David G., 1961. Rhododendrons of the World , New York: Charles Scribner's Sons.