Rhododendron problems
 

We have a large, ~40 yr. old rhodo, quite spindly, about 15'-20' tall
that is looking quite sick. Very yellowish green leaves, sparse, some
leaves with brown spots on them. It is flowering now but even the
flowers do not look healthy. The bed was mulched last year and
10-10-10 basic garden fertilizer spread over the bed, but that does
not seem to have helped this rhodo.

We have had a hot dry spell the past 2 weeks (Victoria BC) and
although we have an irrigation system I have also just given the tree
a good thorough watering today.

Any ideas appreciated on how we might save this rhodo would be
appreciated.

Rhododendron problems
 

lagagnon wrote:
We have a large, ~40 yr. old rhodo, quite spindly, about 15'-20' tall
that is looking quite sick. Very yellowish green leaves, sparse, some
leaves with brown spots on them. It is flowering now but even the
flowers do not look healthy. The bed was mulched last year and
10-10-10 basic garden fertilizer spread over the bed, but that does
not seem to have helped this rhodo.

We have had a hot dry spell the past 2 weeks (Victoria BC) and
although we have an irrigation system I have also just given the tree
a good thorough watering today.

Any ideas appreciated on how we might save this rhodo would be
appreciated.

There are several possible reasons, but the most likely is that it could
have Powdery Mildew. Are there brown or grey patches on the underside of
the leaves, which appear as light patches on the top? You will need to
spray regularly with a fungicide active against powdery mildew if that is
the case, but if it's a bad infection, the rhodo may not survive no matter
what you do.

It doesn't look like a nutrient problem, but it wouldn't do any harm to try
spraying/watering it with Sequestrene (chelated iron).

But is it the only rhodo you have exhibiting this problem, or are there
others? Rhodos are pretty long-lived, so I doubt this one has reached the
end of its life through old-age.

Remember that rhodos are shallow-rooted, so if anything has disturbed the
surface around the plant many of its roots might have been destroyed. What
did you mulch it with last year? Is there any chance that there may have
been something nasty in the mulch which has only just appeared?

You could also try asking around. AFAIR there are many wonderful gardens in
and around Victoria/Vancouver and perhaps there are some experienced rhodo
growers there who can shed a light on your problem.

--
Jeff