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Hi,
Could anyone please help me with a problem which I believe is called Chlorosis? Every year I have the same problem with my petunias and Clematis...the veins in the leaves become very pronounced and turn a very dark green, whilst the rest of the leaf turns very pale yellow and then the whole plant eventually dies.
Any advice much appreciated :)
Mia

Try http://www.penpages.psu.edu/penpages_reference/29401/29401162.html or http://plantclinic.cornell.edu/treeshrub/clematis.htm .