For what purpose, Guest? Would have been better in ericaceous compost, so if its looking chlorotic (yellowing leaves) give it a shot of Sequestrene iron tonic every six months, and use a specific acid feed such as Miracle Gro for azaleas, rhododendrons. Do not feed now though, wait till spring, but you can use the sequestrene now.

try replacing the top couple of inches with ericaceous compost and feed with a acid feed like miro-acid plus the sequestrion when you see pale leaves.