United Kingdom

I have a lot of pot plants at the front of my flat which is on abusy road, They usually thrive but this year quite a few of them - geraniums, a small peach tree and a fuschia among others are getting dark purple leaves. I put some compost on them earlier this year & a bit of baby bio. Could this be causing the dark colour? What can I do to bring them back to normal?

• 20 Apr, 2008