Charlie Pridham wrote:

"Rachel Sullivan" wrote in message
news
In article , Nick Maclaren
writes
In article ,
Rachel Sullivan wrote:

Mary Toomey & Everett Leeds, in their excellent book on clematis reckon
montana's are hardy from zones 7 to 9 - that is not as tough as the
large flowered hybrids and viticellas that are hardy from zones 4
upwards. But it's still minus 17.7 to minus 12.3 C - which is still
pretty darned cold.

I assume that you mean USDA zones. Those are relevant in the USA,
and don't apply to the UK. There are lots of plants that are hardy
to zone 7 in the USA, and are tender in the UK (i.e. are hardy down to
only what would be zone 9b).

I know they don't apply to the UK but it gives a rough idea especially
as the OP was from Abroad. (Mary's book uses them in Europe as well.)

C. montana isn't one, though, and it is extremely unlikely that it
was killed by the frosts mentioned. I have not heard of "slime flux",
but some fungal or bacterial infection seems most likely.

Yes, I think so too. Slime flux is the only problem I've ever had with
montana's (that was caused initially by frost) and that's only coz I
deal with so many. I should think that most people never come across
it.

--
Rachel
I have some great slides of it Nick!, bright orange slime (as the name
suggests) I have seen it on Montanas, C. grata, and suprisingly, late pruned
C. viticellas (although its not a big problem with the last as they regrow)
However I think Roger may have noticed the slime! so as you suggest some
sort of root rot is possible especially if it has been wet during winter.
But the burst pipe idea is quite true and I think it pays to hard prune
Montanas in June from time to time to avoid having one thick trunk.
Like Rachel I thought grandiflora was the toughest but I lost a ten year old
plant a couple of years back, not replaced as I reckon there are better
scented plants.

--
Charlie, gardening in Cornwall.

Hi Charlie
"Bright orange slime", yes, I suppose I would have noticed that, if it
had been there. Unless it has a tendency to disappear totally in just
a few days.
So I'm left with the fact that two old plants with thick stems are
totally dead to the ground after the last freeze.
I had a talk with a local Clematis grower, yesterday. He is of the
opinion that Clematis montana, old plants especially, have a tendency
to die when there is a severe cold spell in spring, when the sap is
already rising. At least over here. He has not noticed that "orange
slime", but has seen many times old montanas die after a cold spring
freeze.
The amazing fact (to me) is that young plants seem unaffected. These
Clematis montanas of mine did seed themselves. And I just noticed two
of those seedlings, just a few cm. high, that are now producing leaves
- they did survive the winter perfectly well, in the same location,
totally unprotected.
And, thinking it over, I do not know of really old (thick-stemmed)
montana's nearby. Nothing like those that I saw in the UK. I suppose
something like "slime flux" must be especially active here.

Just another thing, Charlie. Remember the Ercilla volubilis that I
bought? It was just a yard away from one of the C. montanas, climbing
the same wall. And it has survived perfectly, just the tips are a bit
scorched. So, as far as I'm concerned, Ercilla seems hardier than C.
montana :-)

Regards,
Roger.