Variation in early winter hardening within families of Pinus sylvestris (L.) from Northern Sweden

Abstract

Containerized one‐year Scots pine single‐tree families from open‐pollinated seeds collected in (i) a natural mature stand in Korpilombolo (lat. 66°53'N and (ii) a 35‐year‐old field trial at Nordanås (lat. 64°18'N) were freeze‐tested at ‐10°C to study the variation between families with respect to early cold‐hardening in the autumn. There was a significant variation in cold‐hardening between single‐tree families from the Korpilombolo stand. There was also a significant variation in cold‐hardening between progenies of trees within families in the Nordanås field trial. The cold‐hardening of a progeny was positively correlated with the level of needle attachment to the current year lateral shoots of the mother tree in early August. Observation of needle attachment in late summer was suggested as a method of screening for early cold‐hardening in breeding Scots pine for northern localities.