Abstract
Freezing in leaves of N menziesii was monitored by experimental freezing of attached twigs and seedlings growing naturally in a forest site and compared with a routine laboratory test in which excised plant material was used. Major differences in ice nucleation were observed: ice formed in attached leaves in situ at temperatures that were on average 4°C higher than in excised leaves, in both seedlings and adult trees. Excision did not affect the symptoms of frost damage. Mean foliar frost resistance was 2°C lower in seedlings than in mature shoots, and about 1°C lower in shoots measured in situ than in excised shoots.