Effects of root pruning and stem injections with Gibberellin a 4/7 on flowering and cone harvest in three Picea abies seed orchards

Abstract

The effects of root pruning and stem injections of gibberellin A 4/7 (GA) on flowering and cone harvest were studied in three mature Picea abies (L.) Karst. seed orchards. The trials were split into two consecutive years, two in the summer of 1988, the third in summer 1989. Both years could be regarded as good years for natural induction of flowering. No effects were found on male flowering, whereas female flowering was enhanced by root pruning in two trials and by GA injections in one. No interaction effects on either male or female flowering were detected. In two trials, an approximately three‐fold increase in number of cones per tree was obtained after root pruning and GA injections, which is a commercially acceptable increase.

Key words:

• cone production
• GA 4/7
• Norway spruce
• promotion of flowering
• root pruning
• stem injections.