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Print date: 9/26/2017

Lepidote Rhododendrons

29 October 2015 @ 07:27 | Posted by C. J. Patterson

Rhododendron enthusiasts are often asked what they mean when they refer to a rhododendron as a "lepidote". The confusion is compounded when one sees quite a bit of space devoted to lepidotes in flower shows.

A nurseryman may tell you casually that it refers to the small-leaved evergreen rhododendron. This can be used as a generality...but not as a hard and fast rule...as there is a fair amount of overlap between lepidotes and the "large-leaved" elepidotes.

Real traits that make it a useful distinction is lepidote rhododendrons have scales on the underside of the leaf which protect the plant's stomata (leaf pores) through which oxygen, carbon dioxide, and water vapor pass. The scales evolved originally to regulate moisture, to help keep water in the cells in dry times, and help shed it in times of surfeit . This allowed plants evolving in the tropics to live in the quick-drying forest duff on the very thin soils of the tropics, or even epiphytically on rocks or tree trunks. Turn a leaf of the lepidote over and look for the tiny scales; some are big enough to see with the naked eye, but a hand lens will reveal a world of otherwise hidden detail. Elepidotes, on the other hand, are without scales to cover their stomata.

But winter brings many of the same demands as the tropics on a plant...encasing it in wet snow or desiccating it with cold dry winds, and the scales evolved to become adept at dealing with harsh winters as well. As a result, lepidote rhododendrons have adopted and spread to nearly all environments, from tropical jungles and Siberian woodlands to mountain meadows and alpine tundra. Because of this wide tolerance of soils, temperatures and exposures, they are especially useful to gardeners in the Northeast United States. Other adaptations, such as fast regrowth after predation from grazing animals, and early bloom to deal with short growing seasons in cold climates, give us a plant that is easily pruned to shape and early to give the gardener a boost after a long winter.

Most lepidotes have axillary buds...extra flower buds under the terminal flower bud or along the branch...and in bloom often smother the foliage until all you can see are the flowers. Lepidote species range from tiny creeping alpines suitable for the rock garden to tall forest and meadow plants for woodland wildflower gardens and formal borders.

Best of all, the hybrids developed by plant breeders bring hybrid vigor to the party, giving us a huge range of plants, among them some of the easiest and the hardiest rhododendrons to grow in cold climates. A commonly grown lepidote cultivar is "Rhododendron 'PJM', which was hybridized by the Mezitts, and is now grown and admired all around the gardening world.

The large-leaved fancy varieties of rhododendrons may get all the big press...but for vigor, hardiness, adaptability, easy of culture, and sheer traffic-stopping, eye-popping show of flowers in the spring...my money is on the lepidotes!

 From the Massachusetts Chapter Newsletter, September 2006.