The first rhododendron to be introduced to Britain was R. hirsutum (the ‘alpenrose’) from the Swiss Alps. It is believed that Huguenot refugees may have brought the plant to England in the 16th Century. It was a disappointing plant, which never grew as well as those specimens seen growing in the alpine meadows.
The next rhododendron to arrive in Britain was R. maximum in 1736 from America. The advantages of this plant was its hardiness and ability to flower late thus avoiding the early frosts. However it is not very decorative with small flowers almost hidden by the newly emerging leaves. It is also known as ‘Rosebay’, ‘Great Rhododendron’ or ‘Great Laurel’. R. maximum is probably responsible for the blotch or spot in the flowers of many hybrids and several of the rhododendrons raised by the Waterers of Knaphill and Bagshot Nurseries before 1850 have this characteristic.
R. ponticum was first discovered in Spain by Alstroemer, a pupil of Linnaeus in about 1750 and it arrived in England via Gibraltar in 1763. It is too tender for large parts of Europe and North America and is found indigenously in the Caucasus and Northern and Eastern Turkey and Northern Spain. R. ponticum with a yellow blotch comes from NE Turkey. The most important role of R. ponticum has been in the development of hybrids where it has been used as a root stock for grafting. This gives the hybrids enhanced vigour and has allowed them to be produced cheaply and in large numbers. Unfortunately in many cases the root stock plant takes over from the hybrid and if these growths are not removed the plant will revert to the original R. ponticum. This is the reason why many rhododendron plantings began as interesting hybrids but with neglect have became the common ponticums again. An example of this is the ‘Rhododendron Gardens’ on Bidston Hill, planted by Lord Vyner, that lie to the north of Boundary Road, some distance away from Park Wood on Bidston Hill.
R. caucasicum, a scrub plant from the Caucasus mountains, came to England as a gift to Sir Joseph Banks from the Russian collector Count Pushkin in 1803. It is somewhat variable in colour, mostly in shades of pink with some spotted forms and is low growing and compact. It layers freely which is passed on to many of its hybrids. As with many of the early species, selected forms were raised and named and one or two of them are still in cultivation today. R. caucasicum ‘Roseum’ is a good pink form and R. caucasicum ‘Pictum’ (found on Bidston Hill) has a definite blotch in the flower. A cross between R. ponticum and R. caucasicum produced R. ‘Cunningham’s White’ (also found on Bidston Hill) which is an excellent plant for tolerating industrial pollution in cities and was widely planted in Birmingham where large specimens can be seen today. R. ‘Cunningham’s White’ is now the preferred root stock plant for grafting as it is not invasive.
R. catawbiense, introduced from America in 1809, grows in the wild in North Carolina and Virginia. It is not as vigorous as R. ponticum but it is extremely hardy and can withstand 60 degrees of frost, which occurs regularly where it grows on the banks of the Catawba River. It is a neat rounded bushy plant with relatively insignificant flowers. The two cultivars, which are still available today are R. catawbiense ‘Boursault’ (lilac tinged with rose) and R. catawbiense ‘Grandiflorum’ (lilac) (found on Bidston Hill).
The next species to be introduced to Britain in 1810 was R. arboreum from the Himalayas. It first flowered in Hampshire in 1825. The significance of this plant is that it brought the colour red into hybrid rhododendrons and all the early deep-coloured forms derive their colour from this species. R. arboreum is not very hardy especially in the darker coloured forms, but when used as a hybrid it does not pass on this trait. In the Himalayas it grows very tall and is often described as the ‘Tree Rhododendron of the Himalaya’ and this has the effect of making some of the hybrids very straggly in growth. R. arboreum was used to produce R’ ‘Nobleanum’ (one of the earliest rhododendrons to flower), a hybrid between R. caucasicum and R. arboreum, which was given the Royal Horticultural Society’s Award of Garden Merit (AGM) in 1926.It was bred by Anthony Waterer of Knaphill Nursery, but named after Charles Noble who ran Standish & Noble Nursery in Sunningdale.
In 1849, Sir Joseph Hooker introduced R. griffithianum, a species rhododendron with large bell flowers, milky white in colour and a subtle fragrance. It is not entirely hardy and can only be grown in the open in Britain in sheltered gardens. Also it is tall growing and can become very leggy, a trait which it occasionally passes on to its hybrids. The first crosses with R. griffithianum were made with hardy hybrids such as R. ‘Album elegans’ and the most famous cross is the popular R.’Pink Pearl’ (found on Bidston Hill) which owes much of its beauty to R. griffithianum. The exact parentage of R.’Pink Pearl’ is not known although it was bred by John Waterer and was given the RHS Award of Merit (AM) in 1897.
Another species collected in the Himalayas by Sir Joseph Hooker on his successful expedition in 1849 was R. thomsonii which also had some influence on the development of popular hardy hybrids. It is tall growing with rounded leaves and blood-red flowers, which are cup-shaped and have large calyces. Many of the R. thomsonii seeds brought back to Englind by Sir Joseph Hooker were raised in the Berkshire Nurseries of Standish & Noble. By grafting some scions onto a very old standard rhododendron they were able to produce flowers within a few years and used these to raise R. ‘Ascot Brilliant’ an early flowering (March-April) red hybrid (found on Bidston Hill). The introduction of R. thomsonii marked the end of an era, the period of exploration in the Himalayas, which had brought many fine new species into cultivation. These plants had improved the quality of the hybrids produced from the original North American and European species and from the first Himalayan rhododendron of them all, R. arborium. By 1900, the development of the old style hardy hybrids had more or less run its course. In JG Millais “Rhododendrons” Volume 1 in 1917, he lists 484 hardy hybrids raised in Europe and available at that time, of which 292 oiginated from the Waterer Nurseries at Bagshot & Knaphill.
Knaphill Nursery in Woking, Surrey is one of the oldest nurseries in England; Michael Waterer founded it in the 1790’s. In the 1860’s most of the stock was imported from America and increased from seed with the result that many fine hybrid rhododendrons were produced. During 1894 Knaphill sold over 13,000 rhododendrons and it is possible that the rhododendrons planted in Park Wood came from this nursery in 1897 and 1900 when hardy hybrid rhododendrons were planted. Donald Waterer sold the nursery in 1976 to Slocock Nurseries. The current Knaphill-Slocock catalogue contains some 150 rhododendron hybrids.
- “Rhododendrons and Azaleas at the Knap Hill Nursery” G Donald Waterer 1950
Extract from the Quarterly Bulletin of the American Rhododendron Society Vol4 No 1, Jan 14 1950.
- “Rhododendrons” John Street, 1987, Globe Pequot Press, Chester, Connecticut
- Hirsutum.info: About Rhododendrons, Azaleas and Vireyas; a virtual arboretum
- The Rhododendron, Camellia & Magnolia Group of the Royal Horticultural Society.
Source: M.K. Knottenbelt 2004