Effects of early long-night treatment on diameter and height growth, second flush and frost tolerance in two-year-old Picea abies container seedlings

• Published in: Scandinavian journal of forest research 2007-10, Vol.22 (5), p.375-383
• Main Authors: Kohmann, K, Johnsen, O
• Format: Article
• Language: English
• Subjects: altitude; Autumn shoots; budbreak; buds; cold tolerance; conifer needles; container-grown plants; critical night length; growing season; height; latitude; photoperiod; Picea abies; planting; provenance; root collar diameter; root collar growth; seedling production; seedlings; shoots; summer; temporal variation; tree growth; trees
• ISSN: 0282-7581; 1651-1891
• DOI: 10.1080/02827580701520486

The object of this study was to obtain Norway spruce seedlings with buds set, ready for summer planting from 1 July. An early long-night treatment prevented flushing of the newly formed terminal buds and ceased height growth, but slightly reduced hardiness in buds and needles. Nevertheless, a sufficient hardiness level in the autumn was acquired at a Norwegian nursery at 59°46′ N, with plants of the local provenance given a long-night treatment (14 h) for 13 days from 25 June. Similar treatment at a nursery at 64°30′ N did not give the same result; all treatments led to a second flush with resumed growth of the local provenance. A trial with seed lots from several provenances was therefore performed at this nursery, and a significant correlation was found between the critical night length of the seed lot and their ability to produce non-flushing buds; the longer the critical night length of the seed lot, the fewer non-flushing buds. Responses at the northern nursery are probably due to the lack of a dark period after termination of the treatment, and too short a treatment period to attain bud dormancy. An early and successful long-night treatment will also produce shorter seedlings with a larger root collar diameter.