On 28/05/2010 10:54, Eddy wrote:
Donwill wrote:


The main problem with rhododendrons is that the hybrids that you
purchase in most nurseries are propagated by grafting on to ponticum.
The result is that the ponticum takes over unless they are carefully
watched. I would always when buying rhododendron hybrids to ask the
seller whether they are grafted or propagated on their own roots. My
advice is to REJECT GRAFTED HYBRIDS.

Regards
Don

Many thanks for this interesting info, Don. I've just rung the nursery
where I bought our rhodies and asked them whether their rhodies are
grafted onto Ponticum or propagated on their own roots and they have
assured me that all of the rhodies they sell are propogated. So that's
a relief.

But, just out interest, when you say that in the case of grafted rhodies
the ponticum takes over "unless they are carefully watched", what do you
mean by the "watching"? What is it that one can do in such cases to
stop the Ponticum taking them over?

When I begin instructing those in this area who live in fear of all
rhodies, it would be good to be armed with this knowledge as well and to
be able to speak with what may come across as real expertise! :-)

Thanks.

Eddy.





I'm not an expert Eddy, however, ever since I became interested in
gardening I 've been aware of the dangers of buying hardy hybrids from
nurseries by reading favourite books on the subject.

Ref -Michael Howarth Booth (MHB),The Flowering Shrub Garden, 1947, P59,
"Nursery bought plants are usually grafted on R.Ponticum, which will
cause endless trouble with suckers unless the bushes are planted about 4
inches deeper than before,with peat, only, put on to cover the roots up
to within 2 inches of surface level, and finally a mulch 6 inches deep
of leaves or June cut bracken, put on over all."

Ref - MHB, The flowering Shrub Garden Today, 1961, P77.
"When a bed is planted up solely with grafted hybrid rhododendrons, the
whole thing is apt to be overdone so that we get an overpowering
concentration of flowers at one time and an unrelieved hump of dark
green for the rest of the year. Culturally it is disastrous, for
rhododendron fly and bud blast run riot through such mono-cultures, the
ponticum rootstock smothers the scions unnoticed and eventually a vast
dark catacomb beneath high straggling branches leads to the whole thing
being sooner or later felled to the ground. The ponticum, then,almost
alone survives"
P78.- "if grafted, ponticum suckers are promptly spaded off."

Ref - Cox & Cox, Encyclopaedia of Rhododendron Hybrids, 1988, P10.
" due to the use of the over-vigorous ponticum being used as a rootstock
to graft most hybrids, the rootstock usually throws vigorous suckers
which if left unattended soon smother and kill the hybrid grafted on top."

I've extracted a few ref's above,
MHB recommends spading the suckers off, I'm not sure if that's a bit
drastic, however you could I suppose treat them like rose suckers,
either you cut or pull them off.
I've always planted them a bit deeper than normal, and as an insurance,
any convenient low branch I have layered by abrading the bark and
placing a stone on it to press it down into a bed of acid compost .

Hope this helps
Good Luck.
Don