Posted: 24/04/2017 at 20:35
Rhododendrons do not cope well with any alkalinity in the soil or their water so you need to get a soil test kit from your garden centre and test the soil for being either neutral or acid which is OK. However, if it's alkaline, you'll need to dig up your rhodo and plant it in a large pot with ericaceous compost. Cover the drainage holes with crocks to allow free drainage.
If your tap water is hard, you also need to collect rainwater to use for watering, especially in a pot. You can also use a solution of sequestered iron which helps ericaceous plants access iron, an essential mineral for plant health.
Another consideration is competition for nutrients so, if your soil is OK, clear all that grass from around its base to a width at least 6 inches beyond its current size and then mulch it with something like chipped bark to a depth of at least 2". This will help retain moisture as well as keep down weeds.