White flowers with greenish-yellow markings open in late spring on a compact, unusually adaptable shrub. Rhododendron catawbiense 'Cunningham's White' grows 5 to 6 feet tall and 6 to 7 feet wide in part shade to full shade, hardy from Zone 5 through Zone 8.
This is the rhododendron most tolerant of imperfect soil, handling higher pH better than nearly any other, which is why it is used as a grafting rootstock across the industry.
The large-leaf rhododendrons hold their foliage year-round rather than thinning like the small-leaved types. Below about 25 degrees the leaves droop and curl up, curling tighter the colder it gets, and they open again within hours once temperatures rise. It looks alarming the first winter and it is entirely normal, a water-conserving response rather than a sign of trouble.
It also takes deep shade and urban conditions. Acidic soil is still preferable, roughly pH 4.5 to 6.0, with good drainage and steady moisture, but this one is more forgiving than most if the ground is not ideal.