The white-flowered Cunningham's White is one of the best-selling varieties in Finland and is annually imported in large quantities from the Netherlands. It is not, however, very hardy without snow cover. The buds will withstand temperatures of not lower than -21oC and the height of the shrub is often determined by the depth of snow around it. It is nevertheless a tough variety and puts out new shoots in summer to replace the ones that died.
With a good blanket of snow, Cunningham's White will winter well at Mustila and sometimes blossoms abundantly. But then Mustila tends to have more snow than many other parts of Southern Finland.
There are several Cunningham's White clones on the market that differ in, among other things, the size of the yellow-green dots and the shades of the flowers. Cunningham's White blossoms at the end of May. In some places it may blossom in the autumn, too, but this then means fewer flowers the following spring. Autumn blossom is very rare at Mustila.
Cunningham's White is widely used as rootstock for other rhododendron varieties and it is thought this may check the growth of many otherwise strong-growth varieties. It does not, however, produce as many rootstock suckers as the Common or Pontic Rhododendron (R. ponticum) previously used for propagating. If a rhododendron with red flowers unexpectedly produces white ones, the reason may well be due to Cunningham's White rootstock suckers, and these should be removed.