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I went down to check on the greenhouse (unheated) and quite a few of the plants, the pelagonium I am plant sitting in particular, have a white mould growing on some of the leaves/ stem ends. Is this OK/ normal? what can I do to stop it. I guess it maybe a ventilation thing?

Sounds like botrytis

http://www.gardenaction.co.uk/techniques/pests/mildew_botryitis.htm

FWIW I open up the doors of my greenhouse if it's mild -and then forget to close them >:( This seems to keep mold a bay over winter.

Jeremy

Woolly aphids?

Woolly aphids are insects, mould is a fungus :-\

thanks guys, have been opening the door on milder days and have spaced the plants out a bit better - hopefully will see some improvement.

Quote from: daisymay on January 09, 2006, 16:56:44
have a white mould growing on some of the leaves/ stem ends

Quote from: Merry Tiller on January 11, 2006, 23:16:25
Woolly aphids are insects, mould is a fungus :-\

Botrytis is called grey mould for a reason. Daisymay would not be the first to mistake woolly aphids for a fungus.
Botrytis cinerea is considered a weak pathogen and is generally found on tissue previously damaged or attacked by another pathogen or on newly formed tissue. Daisymay makes no mention of other symptoms, such as brown stems or leaves, which makes me think it may not be Botrytis.

some of the leaves on the pelagonium have gone brown and died as well, didn't think to mention it as I figured this was normal for a plant that should die back over winter. So much to learn and think about!

The leaves are not crispy though, kind of soggy and limp when they go brown, which made me think the condensation/ dampness of the grrenhouse was a part of the problem??!!

QuoteDaisymay makes no mention of other symptoms, such as brown stems or leaves, which makes me think it may not be Botrytis.

Quotesome of the leaves on the pelagonium have gone brown and died as well, didn't think to mention it as I figured this was normal for a plant that should die back over winter. So much to learn and think about!

Doh! ......................... You spoke too soon methinks Mr M.

Quote from: daisymay on January 15, 2006, 15:44:40
some of the leaves on the pelagonium have gone brown and died as well, didn't think to mention it as I figured this was normal for a plant that should die back over winter. So much to learn and think about!
The leaves are not crispy though, kind of soggy and limp when they go brown, which made me think the condensation/ dampness of the grrenhouse was a part of the problem??!!

Yes, your problem is static damp air. Spacing the plants out is a good move. Also, watch the watering - the plants want to be moist, not wet - over-wet soil encourages all sorts of pathogens. Get rid of any brown leaves, too. Pelargonium leaves die by yellowing slowly, then going beige and crisp - other types of death are a sign of problems. In their native habitat they don't die back at all, just keep going.

Quote from: Merry Tiller on January 15, 2006, 22:14:59

Quotesome of the leaves on the pelagonium have gone brown and died as well, didn't think to mention it as I figured this was normal for a plant that should die back over winter. So much to learn and think about!

Doh! ......................... You spoke too soon methinks Mr M.

No. The description is not detailed enough to make a definitive diagnosis (which is why my first post here had a '?' in it). It may or may not be woolly aphids, I have even read articles by professional researchers who describe woolly aphids as mould like, it may or may not be a mould or fungus. Premature leaf senescence has many causes, including infestations by fungi, insects, such as aphids or red spider, nutrition, pH, etc.etc.. Premature leaf senescence on one species of plant does not address the similar symptoms on the other plants that Daisymay mentions either.
I do not, however, have any doubt in Daisymays ability to tell white from grey. It seems to me to be the problem with your diagnosis that cannot be ignored. If it is a fungus then the very common Sclerotinia scelotiorum is far more likely to be the problem- it's white for a start!

Spare me, I'm feeling embarrassed for you :'(

Maybe a little less reading and a little more thinking would be a good idea, I've come across the mealy mouthed text book brigade before but nothing beats the experience of an experienced practical gardener.

Face it, I was right, you were wrong and you know it, it's not the end of the world.

Tip: if you're in a hole already, stop digging ;D

I have just read the link you have referenced. Perhaps you should read the link too? It quite specifically calls Botrytis grey mould in the heading! 
I would also point out that I am not having to reference any reading material but am relying upon my 32 years of professional practical gardening to challenge your diagnosis.
Isn't marginalisation of someone else's comments by how they are percieved a little archaic?

Back to the subject. ;)

Our neighbour sprays with copper sulphate- the stuff you spray on potatoes - when he sees mould starting in his greenhouse and his problem goes away. It can't be for blight ;D don't know if this is helpful to know? :)

(the pelagonium I am plant sitting in particular)

I would clean up the above, remove all effected leaves and bring inside to a ventalated room and dont water.