Customers will be able to collect used coffee grounds across Costa stores nationwide for free from 13 July.
Fortey said: "I have been using Costa's coffee grounds on my cabbages for some months now and I've seen a huge improvement in the quality of my veg.
"Coffee grounds are an excellent source of slow-release nitrogen, calcium and magnesium that are greatly beneficial for the growth of plants. As well as a soil conditioner they have been used to protect the plants from snails and slugs and this has helped save me money and get the best out of my veg."
Costa corporate responsibility head Kerry Parkin said: "This is yet another example of Costa’s ongoing commitment to making our business more sustainable. Our new Costa ‘Grounds for Grounds’ initiative is one of the many ways we are diverting waste from landfill whilst giving back to our customers."
Other unused grounds will continue to be collected by waste specialist Biogen, converting the grounds to bio-gas, used to power some of Costa’s dual fuel vehicles.