On May 5, 12:56*pm, Chris Hogg wrote:
On Fri, 4 May 2012 15:27:27 -0700 (PDT), lagagnon
wrote:

We inherited a very old scraggly large rhododendron. It was never in
very good shape and we have done a lot to try to improve its health:
extra water during dry summers, added iron and added epsom salts,
special rhodo fertilizer. All to little avail.

Some photos of the poor quality lime green leafs and spotting can be
found he
http://imageshack.us/g/17/0001un.jpg/

Any assistance on whether we can do anything further to help this
plant would be appreciated.

Larry Gagnon

Looks like a mineral deficiency of some sort. The trouble is, a number
of deficiencies can produce yellowing leaves with reddish or bronzed
edges, much like yours. For example nitrogen, magnesium and potassium
deficiencies will all give those symptoms.

I see that it appears to be in full sun, and bearing in mind the low
rainfall of the past two years across most of the UK, I wonder if it's
simply been too dry at the roots, when of course it can't take up the
nutrients it needs, so will show signs of multiple deficiencies. I'd
agree with Charlie P; plenty of water regularly and a good thick mulch
(3-4 inches) of acid leafmould across the whole root area, or maybe
rotted pine needles if you have access to a stand of pine trees. Give
it a high-nitrogen feed, watered on monthly (sulphate of ammonia is
best for rhodos) until the end of July, when you could give it a
couple of potash feeds to encourage flower bud set for next year's
flowers. But don't overdo the feeding otherwise you risk burning the
roots, and then you're back where you started with poor nutrient
uptake.

--

Chris

Gardening in West Cornwall overlooking the sea.
Mild, but very exposed to salt gales

I don't know how Rhodo's react to a foliar feed, but I'd try. I'd add
a bit of detergent to act as a wetting agent to help it stick to the
leaves.
Maby something like Phostrogen that has trace elements