P&PDL Picture of the Week for
December 20, 2004

Current observations may explain things later

Mike Dana, Extension Landscape Horticulture, Purdue University

This PJM Rhododendron may look, at first glance, like just a struggling landscape specimen.  But there is more here, once you have a bit more information.  This picture was taken in West Lafayette on December 17, 2004.  As is evident, this spring-blooming shrub is in nearly full bloom, even as the leaves are rolled under due to cold.  The morning temperatures this day hovered around 25º F.

The most interesting thing is what we should all try to remember next year when plants behave strangely or have unusual winter damage.  Woody plant hardening and the onset of dormancy this fall has been most inconsistent.  The first stage of hardening is triggered by short days and that, of course has been normal (and will be, I suppose, until new governor Daniels institutes daylight savings time!)

But the second stage, triggered by low temperatures, has been almost non-existent, with temperatures getting near 60º F as late as into December.  As this rhododendron attests, the physiological condition of at least some woody plants is anything but ready for winter's cold.  What this will mean in terms of plant behavior in 2005 is impossible to predict.  Much depends on the weather soon to come.  But it is a good reminder that keeping good mental notes about current climate conditions can often help explain apparent oddities during the next growing season.

Click image to enlarge

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service