How long has the plant been in the pot?

Hi Bamboo, it has been in this pot for just over 1 year.

Planted in J I no2.

If its made 15 feet in height, its possible its run out of root room, which is always going to happen over time. Bigger pot, maybe, to extend its potted life a bit more? Otherwise, please post photo of the pot and plant... and anything you can see on the plant that might not be quite right, other than loss of leaves.

One thing i forgot to mention Bamboo is the fact that in the summer it produced loads of new shoots but they rapidly turned brown and never grew so come the spring i will have no flowers as i believe they only flower on the previous years growth. The pot is enormous and very deep. It stands in the sun twice a day and does get very hot. Would a prune help if so when should i do this?

A prune of the topgrowth won't help if the plant is rootbound - what size is the pot, depth and width?

My pot is 18 in wide with depth of 16 in - plastic. Sorry i am having trouble sending pic but i have this confounded Windows 10! Am working to resolve it as my camera is quite old but is compatible!

Well that sounds like a big enough pot, but Clematis armandii is a large climber, reaching 35 feet with a spread of 12 feet in the ground, so its not going to do well contained in a pot for any length of time I'm afraid. New growth appearing and then turning brown and dying back could mean insufficient water, insufficient root room, or an invader of some sort in the pot eating at the roots. I'd turn it out of its pot and check,although I know that's difficult given its height.

Thanks Bamboo, i will try to check root ball. What kind of invader do you think might attack before i attempt this, just in case i might have any indicator around the garden? I am hoping it was down to a lack of water as it was very hot in this part of my garden in the summer. As i said in the spring it was absolutely smothered in flower after it's initial growth. I potted it into J I no2 as it is quite free draining. Should it have some thing with a little more water retention given it is in such a hot place? Would a similar size clay pot help?

With any luck it was because you simply didn't keep up with the watering when it was hot - but I'd have expected new growth by now if it was that. Clay or plastic, makes no difference. Things that might invade at the root, vine weevil, chafer grub, root aphids, even an ants nest - they don't eat plant roots, but they will chew them off to make more room for a nest, but if its ant activity, you usually get black bits on the ground round the pot - which you might not have noticed.

I hope it is the water as well. We have had quite a dry few months here. I have checked but there is no sign of invaders. I will pay close attention to watering and wait to see if there is any response. I think a sign of how dry the pot was, is the fact that i now have signs of weeds growing now but had absolutely none through out the summer!

The pot is about 10 times the size of the original pot, so i would think it still has plenty of room to grow. Just a thought but would regular feeding whilst it was too dry have burnt some roots? Again if that is so, i must improve the watering.

Many thanks for all your help Bamboo!