Rhododendrons are happiest when grown in conditions ranging from full sun to mild shade. Certain Rhododendron varieties, such as 'Caroline,' 'Scintillation,' Yakushimanum hybrids, 'Hong Kong,' and the hardy varieties from Finland, require some shade during the middle of the day; otherwise, the foliage will turn yellow or even burn, which is especially likely to occur during the summer months when the temperature is high.