Different combinations of stem girdles and gibberellin A4/7 (GA4/7 ) stem injections were tested on 17-year-old western larch (Larix occidentalis) in a provenance trial near Enderby, B.C. Trees that failed to flower without treatment produced an average 5 seed cones and 16 pollen cones each in response to stem injections of GA4/7 , at flushing of the long shoots and again 2 weeks later. The six B.C. western larch provenances in this trial differed greatly in their flowering response to GA4/7 . Girdling was ineffective in promotion of flowering, either alone or in combination with GA4/7 . Recommendations are made for the selection and treatment of seed production areas as an interim measure until clonal seed orchards come into production.
Relative to the field-grown trees, potted grafts only 3 years old flowered profusely following a spring root pruning by root weevils. Although not recommended as an induction treatment, this response to root damage is evidence that western larch may be a good prospect for container seed orchards. The potted trees have provided experimental material for much-needed research on pollination and seed development, as well as on the tissue-culture production of haploid plants for this species.
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Updated May 29, 2009