You say Tomatoe & I say tamaydo !!!
Bryony it depends on what you have been brought up on really, like cotoneaster some say cotton easter I have always said cotoniaster also I say Innez too, I don't think it matters, do you? It's only a name, growing them is far more fun.

I agree with Grandmage. But if the pronounciation bothers you...I say Day-leea. and John Innis. (Phoenetical spelling is rather fun isn't it?) I say montana as you say it ,as well. But what the hell?

It is fun listening to Botanists talking about plants. Took us ages to realise what one was talking about, 'Cardamine' which was pronounced car dam in ee with the emphsis on the dam.
As said it really only matters if you need to talk to a person who does not speak your language when the proper Botanical name pronounced the proper way( if there is such a thing) is the only common ground you have.

It is a bit daunting to say a word you have not heard said. It's off putting to get corrected. It's even worse when they change a familiar name and you wouldn't dare pronounce the new one out loud. Helichrysum (strawflowers) are now Xerochrysum bracteatum......only know cos i just read it.....well i never

John Innes is Innis, though I've heard it pronounced differently. But then I've heard plastic pronounced "plaarstic" as well! I say Innis, I say clem-a-tis and clemaytis, depending on my mood, and dahlia is always 'daylea'; and montana is montana, as in the state, as far as I'm concerned. One of my old bosses insisted on pronouncing Peugot as pojo, and always said 'owdeo', when the rest of us said audio.The point of names and words is to make other people understand us - whether you say Inez or Innis shouldn't matter, and anyone who corrects these minor differences is being, hmm, let me see, its a word beginning with p and ending in y with an n and a c and an o in the middle (not in that order) that I can't say on here, so let's stick with pedantic...

Heard a lady in a GC ask for Camp-a-noola which I call Campanula with the emphasis on 'pan' ... this could go on for some time ! : o ) )

You're right, it could go on for some time - I once heard someone in a GC ask for ajuga, saying aguja - but we all knew what she meant.

Bryony for the latin plant names if you really want to pronounce them correctly then either by a book (we have one such and never use - lol) or do a google search. Get 4 gardeners talking about the same plant and you are likely to hear 4 different pronunciations. I say clem-a-tis B says clem-ay-tis we both know what we are talking about and don't fret. He also says baath whilst I say bath. Talking to a mountaineering friend years ago he kept talking about the Him-a-lias - took me a while to realise he meant Him-a- lay-as. An American friend asked if our cats were dos-el I eventually translated this to do-cile!

Just to lay this one to rest a bit, I've looked up what I can in my Plant Names Simplified - clematis is pronounced "klem-a-tis"; montana is "mon-ta-na" (which is how you were corrected) dahlia is "dah-le-a" (as in Dahl), aquilegia is "ak-wil-e-je-a". I'm still saying daylee-a though...

So am I! And I will continue to say clem-ay-tis, mon-tan-a and ak-wil-ee-jia. They're all lovely and surely that's the point?

As latin is a dead language I doubt that it matters so long as we know which plant we are talking about.