Rhododendron ‘Horizon Monarch’ (‘Nancy Evans’ x ‘Point Defiance’) – A 2002 Award of Garden Merit winner with huge cone-shaped trusses (my image is not typical) of pale yellow flowers (with hints of salmon pink) emerging from deep red buds – with the latter showing its ‘Nancy Evans’ roots. Nicely contrasted by large deep green foliage. Grows 6′ high. Zone 7.
Rhododendron ‘Hotei’ (‘Goldsworth Orange’ x [R. souliei x R. wardii]) – This rhododendron cultivar is considered by many to be one of the best yellows, which it why it is an ARS winner. ‘Hotei’ features bright canary yellow blooms in ball-shaped trusses. Like most yellow rhododendrons, it requires well-drained soil. This 1968 introduction grows 3′ high. Hardy to zone 7.
Rhododendron ‘Tow Head’ (syn. ‘Towhead’) (R. carolinianum var. album x R. ludlowii) – Another 1968 introduction which is extremely hardy. ‘Towhead’ features pale yellow to greenish-yellow flowers borne on contrasting reddish stems, usually in late April. The dark green leathery foliage also takes on bronze highlights in autumn. Slow growing to 2-3′ high. Zone 5.
Rhododendron ‘Nancy Evans’ (‘Hotei’ x ‘Lem’s Cameo’) – This is the ‘big wow’ of yellow rhododendrons with amazing golden-yellow (salmon highlights when emerging) blooms emerging from reddish-orange buds from April to May. This RHS Award of Garden Merit winner has oval-shaped deep green foliage. ‘Nancy Evans’ grows 3-4′ high. Hardy to zone 6.
Rhododendron ‘Lemon Dream’ (‘Creamy Chiffon’ x R. degronianum ssp. degronianum ‘Exbury’) – A newer introduction which has garnered a lot of attention, ‘Lemon Dream’ features frilly pale lemon yellow blooms (occasionally double) in early to mid-May. It has strong growth with deep green foliage reversed with brown indumentum. Grows 2-3′ high. Zone 6.