Research Report

FORMAL REPORT: Research Report

THAWING REGIMES FOR FREEZER-STORED CONTAINER STOCK

Prepared for:

The Nursery Technology Cooperative Thompson Rivers University Department of Forest Science Kamloops, BC

Prepared by

Rocky Devon, Project Leader Dianne Jones, Associate Director

September 27, 2011

ABSTRACT

Three thawing regimes were applied over a 6-week period to frozen Douglas fir (Pseudotsuga menziesii (Mirb.) Franco.), western larch (Larix occidentalis Nutt.), and ponderosa pine (Pinus ponderosa Dougl. ex Laws.) container stock: (1) rapid thaw followedbycoldstorage,(2)slowthaw,and(3)freezerstoragefollowedbyrapidthaw.

Seedlings were outplanted to three sites in north central British Columbia. A sub-sample of seedlings was evaluated for root growth potential (RGP) at the time of outplanting. Seedling performance was assessed after the first and second growing seasons. Although there were significant differences among species, thawing regime did not affect seedling growth or survival after 2 growing seasons nor did it affect RGP.

The results indicate that seedlings can tolerate variations in thawing practices that may occur due to weather or other circumstances beyond control. However, it may be best to keep seedlings in freezer storage for as long as possible in order to prevent storage molds.

INTRODUCTION

Freezer storage of container seedlings, although an accepted practice in the nursery industry, is still a relatively misunderstood technique in some forest nurseries and reforestation organizations. Research and experience have shown that freezer storage can be a valuable management tool to a successful reforestation program. Freezer storage gives the nursery greater flexibility by allowing for lifting during late autumn and shipping the following spring. This seasonal variation results in a more balanced work load at the nursery and an effective “surge buffer” between nursery and field production (Hee 1987). Colombo and Cameron (1986) found that...