Variation of bud flushing in Larix decidua clones.

In situ assessments of bud flushing in European larch Larix decidua Mill. clones growing under natural conditions were conducted in the Łęgajny seed orchard, Warmia-Masuria Province, Poland. The 27 assessed clones (among a total of 332 trees) were derived from superior plus trees from six selected stands in north eastern Poland. The analyses were carried out on 15-year-old clones grown in two seed orchard sectors differing in soil moisture conditions (no. 3, a nearly flat surface with southern exposure and no. 5, a flat surface, slightly inclined toward the north and periodically flooded by nearby bog-springs). Apical and axillary bud flushing was assessed in March/April 2014, using a 6-stage scale. Significant differences in bud burst were observed among clones, bud types (apical or axillary), clone provenances and growing conditions in seed orchard sectors. Generally, axillary buds flushed earlier than apical buds. Clones growing in section no. 3 showed earlier bud flushing than in section no. 5. Daily mean temperature during the initial bud burst period (stages 0-3) had no significant effect on bud flushing in a number of clones, however the cumulative temperature in that period was strong correlated with bud flushing for particular clones and provenances which suggests susceptibility to spring frost. Local site conditions (i.e. different soil moisture contents and insolation levels between sectors) as well as decreased temperatures in the first period of bud development had strong effects on bud flushing in European larch clones. [ABSTRACT FROM AUTHOR]