What is high potash fertiliser? I keep hearing it but only know that it's in liquid tomato feed, which is very very expensive to use over summer on all my plants! I currently dig in chicken manure, rose feed granules and mulch with manure in spring, then sprinkle a bit more around in mid-summer , do I also need to feed weekly with tomato feed? On the black spot front, I spray with weak sulphur solution (green gardeners), take off affected leaves and dispose in bin, ensuring that , and I use a paint brush for this, the ground around is coated in the sulphur solution too. The new growth is coming through clear.
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