Jasbird wrote:
Thanks that is a good enough answer for me. I shall probably use less
growmore in future. I've noticed that it seems to have no effect at all
on the plants in my back garden (which has very rich soil).

Found this article which was interesting from a chap in Gardenex ...

Growmore is the standard basic fertiliser for most non proffesional
gardeners but I am not a fan. To start with the nutrient content is 7 ,
7 , 7 . This means that the fertiliser containers equal quantaties of
Nitrogen , phospherous and Potash . Okay fine if you want a general
feriliser . But if you want something more specific for instance with a
higher potash content for say tomatoes or flowers then growmore won't
do .
Growmore has it's place in the garden as an all in one feed , quick and
easy with no messing but it has limited uses if you want to take
gardening seriously .
It's a good beginner fertiliser but you will soon find that it is not
adequate for more specialised subjects .

In my experience there are much better fertilisers around such as
pelleted chicken manure which has the advantage of being organic too .