The Royal Horticultural Society’s garden at Wisley in Surrey is experiencing an unusually early autumn season, with certain tree species dropping their foliage prematurely following an exceptionally hot and dry summer. The phenomenon, termed a “false autumn,” occurs when trees respond to extreme heat and drought stress by shedding leaves ahead of schedule to conserve water, regardless of seasonal cues like daylight hours and temperature drops that normally trigger autumn dormancy.
Trees with shallow root systems, particularly birches, beeches, and sycamores, have proven most vulnerable to this early defoliation. Unlike deep-rooted species such as oaks that can access groundwater reserves, these shallow-rooted varieties struggle during prolonged drought when surface soil moisture depletes. The result is a landscape where expected yellow foliage displays fail to materialize, replaced instead by early reds, ambers, and purples from trees already in distress. Meanwhile, species such as liquidambar continue to thrive, displaying vibrant autumn colors normally expected later in the season.
Horticulturists at the Royal Horticultural Society report that the usual autumn color peak, historically occurring toward the end of October, has arrived substantially earlier this year in drought-affected regions. However, these accelerated displays may prove fleeting, as forecasted strong winds could damage already weakened trees. The organization is responding to shifting climate patterns by gradually transitioning its plantings toward species better suited to future conditions, including Lebanon cedars and swamp cypresses with hardier constitutions and deep, extensive root systems capable of withstanding both cold winters and hot, dry summers.
Experts emphasize that such adaptations represent an ongoing process rather than a novel response. Over recent decades, Wisley has experimented with Mediterranean and Californian oak varieties that have now flourished, suggesting a gradual transformation of the landscape as familiar species become less prevalent in exposed locations while potentially persisting in more sheltered environments.
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