Arduaine Garden in Scotland is well-known in international Rhododendron circles for the number of wonderful species grown here, many of which are considered tender elsewhere and grow unusually under a canopy of mature Japanese larch. To some people, rhododendrons are those unpleasant purple-flowered objects which clog up our native woodlands. This is but one species, Rhododendron ponticum or a hybrid of it which spreads rapidly both by seed and sucker.

Arduaine’s collection is extensive containing about 400 distinct species. The rhododendrons range from the large-leaved giants such as Rhododendron protistum, Rhododendron sinogrande and Rhododendron macabeanum to the small-leaved, high altitude plants which are often classed as rock plants, a sample of which would include Rhododendron fastigiatum, impeditum and orthocladum. In between these two extremes sit the majority of species of differing sizes with a variety of foliage shapes and an astonishing range of flower colour and form. One of the specialities is the only Rhododendron from Ceylon – Rhododendron arboreum subsp. zeylanicum.

Scotland is famous for its Rhododendrons and the Glendoick nursery which provided the comments on growth rates, is worth seeking out. Among special plants are a large number of Rhododendron species and hybrids in the Maddenia subsection, which is probably best known for containing species and hybrids such as Rhododendrons lindleyi, maddenii, ‘Fragrantissimum’ and ‘Lady Alice Fitzwilliam’. Most of these are tender, white and highly scented and can be grown in the conservatory.

Growth Rates of Rhododendrons

• Rhododendrons grow upwards and or outwards at a fairly constant rate from a few cm to 50cm a year depending on the variety. There is therefore no ultimate size. They grow faster in wet conditions than dry areas.
• All azaleas and small leaved rhododendrons can be pruned after flowering to keep them in bounds. This is less successful with large-leaved rhododendrons though it can be successful. Smooth barked species and their hybrids: Rhododendrons. thomsonii, Rhododendrons griffithianum etc do not regenerate when cut back.
• Occasionally one finds wonderful old specimen plants growing out on their own, with no competition from other plants or trees. The thriving plant has formed a perfect shape and is the envy of everyone who sees it. Such plants are the exception, not the rule.
• Individual specimens, planted on lawns for instance, tend to be buffeted by wind, to dry out and to have weeds or grass growing at their roots. Rhododendrons are sociable plants and unless you are prepared to put in the extra work required, don’t dot them around too much.
• Conversely, planting too densely is also to be avoided: there are many once fine collections now reduced to a few spindly branches competing for light with the handful of flowers high up and far out of reach. Planting specimens close together for quick impact is fine if you are prepared to move them or thin them later, but experience indicates this is easier said than done.
• In optimum conditions, rhododendrons live for a very long time: 100 years is not uncommon. Plant with one eye on posterity and you will usually not regret it.
• For Dwarf Rhododendrons and evergreen azaleas plant 60-90cm apart (2-3ft) and deciduous azaleas 1-2m (3-7ft) apart
• Larger hybrids and species 2-4m (7-14ft) apart or even more for large leaved species.

Ancient Mariners Rhododendrons

This picture shows what I call the rime of the ancient mariner as I groweth one of three. Most Gardeners look after the great and small, both bird and beast……

Farewell, farewell! but this I tell
To thee, thou Wedding-Guest!
He prayeth well, who loveth well
Both man and bird and beast.

He prayeth best, who loveth best
All things both great and small; ……