Help - how can I rescue my Clematis

I have two clematis in pots which I am sorry to say I have sadly neglected.  They have been in large pots for about 2 years and produced few flowers.  I think I pruned them wrong; they have a lot of dead looking stem at the bottom but lots of spindly new growth on top.  How and when do  prune these?  Will I always have to have the lower bare stems.  If I plant them out in the garden when should I do it?  All advice humbly received. (The are Ville de Lyon and The President).

Give them a good drink and a tonic of liquid tomato food or seaweed now so their roots get plumped up and healthy as these are the plants' engines.  Keep them watered and fed till late September when you can plant them out in the garden.  

Make sure you dig a good deep hole, twice or three times as deep and wide a syou think they need. Return the soil after improving it with well rotted manure, good garden compost or bought soil conditioner and some bonemeal worked into the soil.   Make sur ethe roots of the clematis are thoroughly wtared before transferring them from their pots to the ground and make sure they're buried at least 6" deeper than they were in their pots as this helps encourage new shoots.  Water them in well but don't prune at this stage.

Ville de Lyon should be pruned back to about 9 to 12" high every spring in March.   It will then produce new stems which flower in mid summer.The President is a bit trickier as it's a group 2 which generallly means it flowers on old wood between May and June.  You then dead head, prune back any unwanted growth and feed it and it produces a second flush of flowers at the end of the summer.  However it can be treated as a group 3 and pruned in spring like the Ville de Lyon.  I would recommend this for next spring and then you can choose in subsequent springs when it's recovered and established itself.

Either way, feed both generously every March with clematis food plus a handful of pelleted chicken manure or blood fish and bone.  Scatter organic slug pellets at the same time as slugs love new clematis growth.  Keep them fed regularly till late June and make sure they don't dry out in droughts.  

Thanks for the detailed advice obelixx, it covers everything I wanted to know.  I will follow your advice and make a note of the correct pruning.  Hopefully I can bring them back to good condition.

Good luck.  They're both lovely clems so are worth trying to save.

you need to plant them deep with shaded feet.Put a plastic ring round it (made from pop bottle)so the slugs cant attack it ,also a few pellets in the ring (birds and animals cant get at them).don't cut right back but tie on to stick and leave till spring to prune and then only if the plant strong enough.you will need to look up what time of year it needs pruning some don't.They need lots of water in spring and feed when the flowers start. once established no problem.I have had that problem when I bought some cheap on offer plants .

Does anyone have any advice regarding powdery mildew on clematis??  I have a Jackmanii which was a cutting from my Dad's plant, and it flourished for three years or so.  However, the last two years it has looked dreadful - the leaves have gone olive/brown coloured with white powdery spots, and the flowers also have white powdery spots and fall off as soon as they bloom.  It is such a shame as it was a magnificent plant for a while.  Can it be saved??  I have been advised to spray it with fungicide every couple of weeks till it completely dies off (which it almost has) it's brown and brittle and looks very sad.  I usually leave it till the spring to prune, but it looks so awful now should I cut it back?  Help!

@ Rozzy - the weather conditions this year have been perfect for mildew - damp with warm days and cool nights - gather up dropped leaves and burn or bag and bin them, then mulch around the plant (not right up to the stems).

Personally I don't use fungicides in the garden, but that's up to you.  Some people use a spray of full-fat milk diluted 10:1 with water and they find that helps. I've not tried it but I might do next year if my honeysuckle suffers as badly as it has done this year.

 Leave your pruning until spring as usual as if you prune now it may start into new growth which will be damaged by the frosts and that will weaken the plant.  When you prune try to encourage the new growth to spread out on the fence or whatever it's climbing up so that the plant gets plenty of air to its leaves - that will help, and mulch again.  Keeping the roots cool and damp while the plant is dry and airy is the key - but so often the weather is against us - but there's always another year