The marvelous hybrid (C. laurifolius x palhinhae) rock rose has performed very well in our wet, humid summers. C. 'Elma' makes a 5' wide x 5' tall clump of woody stems and narrow, dark, evergreen pine-scented foliage. For us, C. 'Elma' has topped out at 3' tall. In early May, the clumps are smothered with large, 3.5", pure white flowers, highlighted by the yellow anthers. There is good reason C. 'Elma' won the RHS Award of Merit. Good drainage is critical for the success of the drought-loving rock roses.