clematis dieback.

can anyone help? I have several clematis of varying types in my garden. Some are on a north facing fence others on east and west facing fences. The problem is that they all sprout healthily in the spring but some (mainly on the north facing fence) start withering at a height of about 2/3 feet and the leaves go brown. However they still grow on and produce healthy leaves and flowers at about 4/5 feet high. Is there any way to avoid this as I'd like the plants to look healthy from ground level

I haven't met this problem myself but I do have some which are bare legged at the base as they are group 1s which are only pruned back if they get untidy and their flowers and foliage tend to be concentrated higher up.   Clematis are very hungry plants so maybe yours are just concentrating energy higher up.   Give them a generous handful of a general feed of blood, fish and bone in late winter or as soon ans new shoots show and then add special clematis or rose food at regular intervals until flowering time or mid July, whichever is later.

Add a mulch of well rotted garden compost or spent planting compost in late autumn and plant something in front to hide the unsightly bits. 

many thanks,

just about the right time to give them a good feed.