However, the BCMOFR-which administers contracts for nursery crops, including cultural guidelines, and subsequently evaluates the crops-needs more than anecdotal information on the effects of different durations of SDs on seedling attributes. For nurseries using a single SD application, the number of weeks used varies. Merrell, BCMOFR, personal communication, 2009). In addition, abnormal bud development after multiple applications of SDs can occur in coastal douglas fir seedlings (MacDonald, unpublished results), which necessitates culling of affected seedlings during morphological grading (R. In coastal douglas fir seedlings, increasing the number of applications of SDs decreased shoot diameter, increased photosynthetic efficiency after −18 ☌ freezing in early fall, and decreased days to budbreak in late winter/early spring ( Turner and Mitchell, 2003). Some nurseries use multiple applications of SDs, separated in time, whereas other nurseries use a single application. The SD dormancy-induction regimes used by British Columbia nurseries are variable. Powelson, BCMOFR, personal communication, 2009). In British Columbia, 51.1 million containerized coastal douglas fir seedlings were planted on government lands between 20 (A. Coastal douglas fir is very important to the economy of British Columbia because its wood is valued in the global market for high-quality structural lumber ( Aubry et al., 1998). Within western North America, the variety extends from California to British Columbia (long. Control of height growth using SDs in recalcitrant, high-latitude British Columbia seedlots of sitka spruce, sitka spruce × white spruce hybrids, and sitka spruce × engelmann spruce ( Picea engelmanni Parry) hybrids and its effects on subsequent performance have also been described ( Hawkins and Draper, 1991 Hawkins et al., 1996 Krasowski et al., 1993).Ĭoastal douglas fir is one of the most important and valuable trees in temperate forestry both within its natural range and as an exotic ( Hermann and Lavender, 1990). Don) ( Krasowski and Owens, 1991 Krasowski et al., 1990), and coastal douglas fir ( MacDonald and Owens, 2006). Studies have compared the effects of a SD regime with a moderate moisture stress regime on seedling morphology and physiology in the nursery as well as performance after planting for western hemlock ( Grossnickle et al., 1991a, 1991b O'Reilly et al., 1989a, 1989b, 1994a, 1994b), western red cedar ( Thuja plicata Donn ex D. Forest nurseries in British Columbia, Canada, use short days (SDs) and/or moderate moisture stress as dormancy induction regimes. menziesii needle initiation bud endodormancy seedling morphology dry weight shoot diameterĪ critical phase of forest nursery culture is dormancy induction because it signals the end of height growth and the start of bud development. We recommend the 3-week duration of SDs for coastal douglas fir crops. After one growing season, duration of SDs had no effect on seedling survival, leader length, shoot dry weight, root dry weight, or shoot diameter. On this date, seedling height and shoot dry weight were unaffected by duration of SDs, whereas root dry weight and shoot diameter were significantly reduced in seedlings given 6 weeks of SDs compared with other durations. In early October, duration of SDs had no effect on bud endodormancy 50% to 88% of terminal buds were endodormant. Needle initiation was completed 10 weeks after the start of the regime in seedlings given 5 or 6 weeks of SDs and 13 weeks for those given 3 or 4 weeks of SDs. During the first week of SDs, budscale initiation started and was completed then initiation of needles for next year's leading shoot (leader) began. In early July, four durations of 8-h SDs were applied: 3, 4, 5, and 6 weeks. We compared the effects of different durations of short days (SDs) as a dormancy-induction regime on bud development, bud endodormancy, and morphology of first-year containerized coastal douglas fir seedlings in the nursery together with seedling survival and growth after one growing season in a common garden.