As a research horticulturist and teacher of gardening courses at the Memorial University of Newfoundland Botanical Garden, I’m always trying to impress upon gardeners the value of foliage. Many people simply look at a plant’s flowers, failing to take into account its “full package.” The trouble with this approach is that a number of plants look attractive for a week or two but are lacklustre for the rest of the season. By contrast, rhododendrons provide year-round interest. A well-grown specimen can be stunning when in full bloom, and the greenery of the evergreen types is welcome during the dreary months of November through March. However, a few rhododendrons go that extra mile with foliage that’s so attractive they’d make excellent additions to the landscape even if they never actually flowered.
My favourite foliage rhododendrons are those with leaves that are densely covered in a felt-like coating of silvery white, cream, fawn or rusty orange hairs on the surface of the leaf (the tomentum) and its underside (the indumentum). In nearly all cases, the tomentum gradually disappears during summer, while the indumentum remains year-round.
The most popular group of these rhododendrons is the Japanese species Rhododendron yakushimanum. Often referred to as the yak rhododendron, it’s among the hardiest of the large-leafed varieties. The plants are compact and generally wider than they are tall. The blooms open bubblegum pink and age to pale pink or white. Then, after flowering, up come velvety leaves that are silvery white to cream. As the summer progresses, the tomentum gradually fades to reveal glossy, deep green leaf surfaces while the undersides retain the cream-coloured indumentum. There are several yakushimanum selections and hybrids on the market.
Another hairy-leafed variety is the bureau rhododendron, a Chinese species. Generally more upright than yakushimanum, it can top more than two metres. New foliage emerges covered in fawn to rust tomentum with bright orange-red indumentum. Later in summer, the tomentum gives way, exposing a shiny, black-green leaf surface, which contrasts dramatically with the orange-red underside. Deep pink buds open to expose pale pink to white blooms. Also available is a close look-alike, called ‘Teddy Bear’, which is a hybrid of bureau and yakushimanum rhododendrons.