The phenology of Eucalyptus marginata (jarrah) was followed at three sites, Churchmans, Karnet and
Ross, in the high rainfall zone of the jarrah forest for a minimum of 3 years. On each site, trees growing
in an area infested with the soil-borne, pathogenic fungus Phytophthora cinnamomi (dieback area) were
compared with trees of similar diameter in the adjacent, uninfested forest (healthy area).
Phenology of jarrah on these dieback sites did not follow a consistent pattern. In the dieback area
at Churchmans, the cambium was active more often, and trees had young leaves in their crown more
frequently than trees in the healthy area, while at Karnet the reverse occurred. This is consistent with
growth measurements. At Ross, in the dieback area, the cambium was active less often but young leaves
were seen more frequently than in trees in the healthy area.
The trees did not flower every year. At Ross flowering started in early October while at Karnet and
Churchmans it started at least 1 month later. New leaves were produced intermittently during autumn
and winter while the main leaf flush occurred in spring and summer. Data from all years showed that
the leaf flush started earlier at Ross than at Karnet and Churchmans. The cambium was intermittently
active throughout the year with most trees growing in late autumn, winter and spring.
Observations of stem growth following unseasonable summer rainfall suggest that cambial activity
is triggered by high, surface soil moisture, but only if soil aeration is adequate. It is unlikely that timing
of the main leaf flush and flowering are determined solely by temperature, soil moisture or photoperiod.
Association of Phytophthora cinnamomi with White Oak Decline in Southern Ohio
