%0 Research note
%T Effect of thawing duration and temperature on field performance of frozen-stored Norway spruce container seedlings
%A Helenius, Pekka
%A Luoranen, Jaana
%A Rikala, Risto
%D 2004
%J Silva Fennica
%V 38
%N 3
%R doi:10.14214/sf.421
%U https://silvafennica.fi/article/421
%X Increasing use of frozen storage in nurseries at northern latitudes  calls for thawing methods that are safe, economical and easy to apply on  a large scale. The easiest and most economical method would be to thaw  seedlings in the same boxes they were stored in. However, doing this  safely requires more knowledge about how long and at what temperatures  seedlings should or can be kept in the boxes without reducing field  performance. In this study, 1-yr-old frozen-stored Norway spruce (Picea  abies (L.) Karst.) container seedlings were thawed for 4, 8 or 16 days  at 4 or 12 °C in cardboard boxes before planting on a reforestation site  and on experimental field in mid-June. Some seedlings were also planted  on these locations after thawing for only 7 hours at 12 °C in order to  separate frozen root plugs. We found some evidence that planting  seedlings after short thawing periods (7 hours at 12 °C and 4 days at  4 °C), under which conditions the root plugs remain completely or partly  frozen, has a negative effect on field performance of Norway spruce  seedlings. Thawing over a 4-8 day period in cardboard boxes at ca. 12 °C  appears to ensure complete thawing of the root plugs and unaffected  field performance, but is short enough to prevent the growth of mould.