Article from Bean's Trees and Shrubs Hardy in the British Isles
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'Therorhodion' from the website Trees and Shrubs Online (treesandshrubsonline.
A genus of two species in N.E. Asia, the Aleutians and W. Alaska. Although often included in Rhododendron it differs from it in the inflorescence, which is a raceme bearing in its lower part persistent, leafy, sterile bracts, the few flowers being confined to the apex of the raceme; the bracteoles on the pedicels, and the bracts subtending the flowers, are also persistent. The inflorescence in Rhododendron is also basically racemose, but does not have persistent bracts below the flowers.