Rhododendron ‘Ramapo’ (R. fastigiatum x R. carolinianum) – A very durable landscape plant and easy rhododendron to grow with abundant pale violet flowers from March to April that smother the matte bluish-green foliage. This is also a good bonsai or container specimen. ‘Ramapo’ is an RHS Award of Garden Merit winner. Grows 2′ high by 3′ wide. Zone 5.
Rhododendron augustinii – A fairly common species rhododendron which was named after Augustine Henry, who discovered it in 1886. This native of China bears bluish-purple trusses on an open, upright shrub with narrow, mid-green lance-shaped foliage. Rhododendron augustinii prefers part to full sun (on the coast) and grows 6-8′ high. Zone 7.
Rhododendron ‘Colonel Coen’ (Rhododendron ponticum lineage) – This mid-sized rhododendron introduced by Ostbo in 1958 is one of the more popular purple cultivars. It produces deep purple flowers (with darker spots) from April to May over glossy dark green foliage. ‘Colonel Coen’ also blooms at a young age. Grows to 5′ high in 10 years. Hardy to zone 6.
Rhododendron ‘Purple Gem’ (R. fastigiatum x R. minus var. minus Carolinianum Group) – This sister plant to ‘Ramapo’ is equally valuable in the landscape with its sun tolerance and ease of growth. ‘Purple Gem’ produces deeper violet blue flowers than ‘Ramapo’, flowering from March to April. The new growth is blue-tinged and it grows to 2′ high. Zone 5.
Rhododendron ‘Bob’s Blue’ (R. ‘Ilam Violet’ x R. ‘Blue Diamond’) – A unique rhododendron with a compact but upright growth habit. ‘Bob’s Blue’ bears electric blue spherical trusses of funnel shaped flowers in May. The small deep green leaves (glossy) are well spaced and take on a bronze tint in winter. ‘Bob’s Blue’ grows to 3′ high and is hardy to zone 7.