There are entire books written about this group of rhododendrons, so I will have to condense this article quite a bit. The species we will learn about are the ones with the largest leaves, and most thought of as the 'Big Leaf' or 'Large Leaved' rhododendrons. All of these species come from the same area of the world in or around the Himalayan regions of southern China, Nepal, Bhutan, Sikkim, Burma, Tibet, and Arunachal Pradesh. This is an interesting part of the world where high altitudes meet on or near the equator. This combination offers a cool, moist growing climate with moderate winter temperatures. Most are found in forests, on steeps slopes, and with mixed trees. 

Species examined:

Falconera subsection

R. falconeri

R. hodgesonii

R. arizelum

R. rex ssp. fictolacteum

Fortunea subsection

R. calophytum

R. praevernum

R. sutchuenense

Grandia subsection

R. grande

R. magnificum

R. protistum

R. montroseanum

R. macabeanum

R. sinogrande   

In cultivation since 1850  and first described by Hooker in 1851, this attractive large leafed rhododendron is native to Nepal and W. Arunachal Pradesh 9,500-14,000 ft. The favorite firewood of sherpas and porters in east Nepal. Also used for cups, spoons and yak saddles while the leaves are used for plates and for lining baskets. The flowers are rose-pink in color and come out in March or April.  

In cultivation since 1917 and first described in 1920 by Balfor, this species is native to Arunachal Pradesh, Burma and S.E. Tibet, and grows at 10,000 to 14,500 ft on steep slopes, mixed in conifer forests, bamboo forests, and even in open areas. The flowers vary from light yellow to light pink, or even light yellow with a pink blush. The long leaves have cinnamon red-brown indumentum on the undersides. 

In cultivation since 1886 and first described by Balfor. Native to N.W. Yunnan, Szechwan, S.E. Tibet and Upper Burma 10,000-14,000 Ft. One of the best large leafed species for colder areas. Leaves very dark green with rust-brown indumentum on undersides. The flowers are white to light pink, always blotched with spots, often with a pink blush.  The species will grow to 10 ft., making a large mound.

 

Two other similar species include R. praevernum and R. sutchuenense. These species are often considered variations of R. calophytum, as they are so similar. 

In cultivation since 1850 and first described by Wight in 1847, this large leaved species is native to  E. Nepal, Sikkim, Bhutan, Arunachal Pradesh and S. Tibet 7,000-10,000 ft. Long narrow leaves up to 18" with silver plastered indumentum under. The flowers are ususally white with purple blotch and spotting. The species is often tree like with a single trunk, growing quite large, 15-20 ft. tall. As with most large leaved rhododendrons, partial shade is preferred.  

In cultivation since 1931, and first described by Kingdon-Ward, this species is native to Upper Burma, S.E. Tibet 5,000-8,000 ft. The flowers are in clusters of over 35 campanulate bells and are pale lavender to deep rose in color. The dark green leaves are at least 18" in length.  

In cultivation since 1918, and first described by Balfor in 1920, this species is native to W. and N.W. Yunnan, S. E. Tibet, Arunachal Pradesh, N. Vietnam growing between 9,000-13,000 ft. This is one of the largest growing of the large leaved rhododendrons, reaching 80-100 ft. tall and having a trunk of 7 ft. in girth in the wild. The largest in planted gardens may only be 20 ft. tall. The light pink to rose flowers are in clusters of 25-35 flowers, and the blooming time is March to April.  

 

Pictured below is a very large specimen grown from seed by the late Dr. Halvor Braafladt, of Eureka, CA. For many years the Braafladts would have a party when this plant was in full bloom to celebrate its beauty. The plant shown below is 68 years old from seed. Dr. Braafladt was also responsible for creating several fragrant R. maddenii hybrids like R. Patricia Maria and R. Humboldt Sunrise.