In 1996, profuse flowering of aspen (Populus tremula L.) occurred throughou
t Scotland. In response, studies were initiated in Perthshire and Strathspe
y to investigate aspects of flowering, seed production and seed storage of
aspen. The proportions of clones flowering were high, averaging 72 per cent
in Strathspey and 77 per cent in Perthshire. The sex ratios were 1.8 male
clones to 1 female clone in Strathspey and 1.3 male clones to 1 female clon
e in Perthshire, which are within the range of ratios recorded for aspen on
the Continent. Easy and reliable methods of sexing aspen trees in the fiel
d during flowering are described. Seed production per catkin on four female
clones in Tayside ranged from six to 60 seeds per catkin. Seed production
was clearly correlated with the number of male clones in the vicinity of th
e female clones. A simple field technique for artificially pollinating fema
le flowers is described. Artificial pollination resulted in seed production
averaging between 159 and 460 seeds per catkin, i.e. approximately a 12-fo
ld increase over natural pollination. The viability of seed from the two st
udy areas was very high ranging from 94 to 98 per cent. The numbers of seed
per kilogram varied between 7 million and 10 million viable seeds kg(-1).
Seed stored at 6 per cent moisture content following rapid drying, and at -
2 degrees C, retained levels of viability in excess of 95 per cent for at l
east one year. The results present excellent opportunities for increasing t
he supply of planting stock of aspen from Scottish seed and fundamentally c
hange current perceptions of the ecological status of aspen in Scotland.