Please advise what species of rhododendron would have the longest blooming season and would be suitable for the Comox Valley region of Vancouver Island.
Early (March-April) ones last longer than those that come out later, as long as they don't get frosted.
As Ron says, the early ones tend to bloom longer because of the cooler weather. We can extend the overall blooming season by planting a combinition of Early, Mid and Late season varieties, however that does not extend any individual plant's length of bloom.
For the Comox Valley, I would suggest R. dauricum or one of its hybrids, like R. 'Olive' (moupinense x dauricum), for example. R. 'Olive' was in bloom here in Langley, B.C. on January 26th of this year and still blooming at the end of March. There is a white flowering form called R. dauricum var. leucanthum which blooms slightly earlier than the pink form, but it is rare in cultivation.
