Hi, I plated one about 6 weeks ago, I added multi purpose compost to the soil but nothing else, I water it every day and it is thriving. I hope this helps.

I'd add some fish, blood and bone and if you have any well rotted compost (from your own heap, or soil conditioning stuff from the garden centre) put that into the hole. It's not essential, but its the one chance you've got to put some composted materials that deep...