This is my poor deciduous rhodendron "Old Gold". It bloomed amazing this spring. But it slowly developed into the symtoms in the photos. Any ideas? The location is in a southern exposure, with sun to dappled sun all day long. Also it has good drainage.
Powdery mildew? This thread may help www.botanicalgarden.ubc.ca/forums/showthread.php?t=15655 with links to more info. A lot of powdery mildew on the large leaved maples here now.
My neighbour recently told me she dissolves baking soda into water for a fungicide. I have a very old rhodo that is about 10' tall and very leggy. It's in a shady spot. Does anyone know how to make it fuller? I'd like to keep as much height as possible.
A pic may help and variety name, possibly a new thread may get more attention. Might search "pruning" in this "rhodo forum".
Plant shown is deciduous azalea with mildew characteristic of these, as is mildew on Gallica roses. You can either live with it (it will keep coming back each year unless prevented ahead of time each year) or attempt control, occurs as a result of combination of plant being genetically susceptible and local summer conditions favoring its development. Foliage mildew of evergreen rhododendrons looks different and is comparatively new to western gardens, probably still unfamiliar to the general gardening public - for some years it appeared it was often mistakenly thought to be cold damage left from the 1990 winter. Different cultivars vary in susceptibility, but a common result with the more adversely affected kinds is for an increasingly gaunt appearance to develop over several years as first the oldest, then the the not-so-old leaves are infested and drop prematurely. The sparse-looking, 10' specimen should be inspected for mildew.