Coniferous planting stock is often held in frozen storage, mostly at −2 °C, for extended periods and then cool-stored (+2 °C) to thaw the root plug prior to outplanting. Thawing is necessary if frozen seedlings cannot be separated from one another and has been advocated by some in order to avoid possible loss of contact between plug and soil with shrinkage of the plug with melting of ice in the plug. Physiological activity is also greater under cool rather than frozen storage, but seedlings of interior spruce and Engelmann spruce that were planted while still frozen had only brief and transient physiological effects, including xylem water potential, (Camm et al. 1995, Silem and Guy 1998). After 1 growing season, growth parameters did not differ between seedlings planted frozen and those planted thawed.