In article , Rod
writes


Slightly acid is OK and is low on lime. If you see pH mentioned in this context
it's a standard measure of
acidity/alkalinity- Logarithmic scale 7 is neutral, lower is acid, higher is
alkaline (limey). Since it is logarithmic 5
is 10 x more acid than 6........ etc
A clay will be better for Rhodos etc if you work in plenty of organic stuff -
well composted chippings, garden compost,
well rotted manure etcto improve soil structure. Ericaceous compost is gilding
the lily a bit but if you can afford it
mixing some in around the plants as you put them in will probably be helpful.
Decent drainage and soil texture is
probably more important than pH so long as you're below about 6.5.

We are over limestone here so we don't normally try to grow
rhododendrons - or we didn't until a totally gardening sceptical
neighbour gave us a sad looking specimen saying, " Here'y'are, this
bloody thing doesn't like me, let's see what you geniuses can do with
it" We bought a 40 litre bag of ericaceous compost, dug a big hole and
set the plant in. It perked up immediately and flowered like mad the
following year - last year. By now the roots must be getting near to our
lime rich soil, so it will be interesting to see what it does this year.
(Yes, I know they are considered to be weeds in some places, but not in
this area.)
--
Alan & Joan Gould - North Lincs.