Jardin botanique de Montréal (Michel Tremblay)
For the plants' leaves roll up in winter as protection from the cold. If temperatures rise above zero, they will unroll and the plants will begin "sweating". Because they cannot replace the lost moisture by drawing more from the frozen ground, the rhododendrons' foliage will
become scorched (especially on large-leafed varieties). By filtering the
sun's rays, the conifers limit the damage.