Always ensure Rhododendron are planted in acid soil, they will not do well in lime soil. To keep acid levels high try adding sulphate of iron to the planting area this will keep acid levels high. For pot planting ericaceous compost only. Not always possibe but in hard water areas of the UK try watering usuing recycled rainwater. Extremely hardy to -10 and beyond these plants require winter protection in the coldest areas only. When planting do not plant to deep Rhododendron are classed as surface rooting plants so ideally plant with the roots just covered.