Hi Steve I can understand your wanting to get the rhododendron out of the pot but why plant in a sunken container instead of the ground? In either case you need ericaceous compost and if your soil is alkaline you will need to keep the rhododendron fed. August is considered the best time to move rhododendrons but you can still do so now.

Hi Thanks for the advise, I intend putting the shrub in the middle of a lawn, so thats my reason for using a sunken container.

Much better to plant in the ground just remove the turf from that area of your lawn and make sure you use ericaceous compost if you have alkaline soil. The rhododendron will thank you for in the long run.

Also leave some bare soil round the plant at least until it gets established so it isn't competing with the grass for nutrients.

Yup agree Steragram

Ok I will take your advise and give it a new home centre position on the front lawn.
Many thanks
Steve.