As one of the few broadleaved plants still in leaf over winter, extra precautions are needed.
On the plus side, this evergreen mountain shrub can remain metabolically active all winter long. But that involves water needs (from frozen ground) and water production in photosynthesis (with the risk of cells burst by freezing.)
So rolling the leaves reduces surface area, creating a higher humidity field around the leaf’s lower surface; the top surface is lacquered in a kind of waterproof coating, the cuticle. The substances in rhododendron’s sap (the equivalent of resin in conifers) acts as a kind of antifreeze.
And the tight rolls offer little for snow to settle on, though we have ample evidence in our woods that wet snows have been heavy winter burdens on the gnarled and spindly shoulders of our mountain heaths, creating low tangles that have long been called “laurel hells”. Just try to get through one, especially with a backpack on!
NOTE: Today will be the warmest day in weeks, only to be followed by an ice storm coming our way tomorrow. Doh!