These New England favorites enliven any landscape and ask little in return.
Photography by Nat Rea
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Come April, after embarrassing months of wearing leaves that look like fat cigars, as writer Eleanor Perenyi once described them, rhododendrons unthaw and launch their show. The knock-out flowers—pink, purple, red, white and yellow—sail aloft for weeks. Sure, there’s a smidgen of labor involved, as in planting, but after that, using our quick-read, make-yourself-an-authority primer, it’s almost a free ride.
Pick and Choose l The cross-pollination of natural rhododendron species (ones that grow wild in North America, Europe, Australia and particularly Asia) has produced today’s bounty of hybrids. Spectacularly diverse, there’s an incredible range of sizes, flowers, colors and foliage. Bloom times also vary. To enhance the enjoyment, it’s best to mimic CCRI and URI professor Dr. William Johnson’s handsome South County garden (a star last season on the Rhode Island Wild Plant Society’s tour). Johnson mixes early, mid and late season bloomers, some 200 varieties in all. But—no panic—just one of each can provide a lengthier display.
Digging In l Rhododendrons prefer moist acidic soil (low pH) and, being ﬁbrous-rooted, a shallow hole (translation: You don’t have to work as hard). Make the hole twice as wide, but only as deep as the root ball, and incorporate plenty of organic matter.
Johnson’s successful routine? “I rototill a spot, add a healthy amount of compost, rototill again, line the hole with compost and set in the plants. I’m kind of lazy so I only go down the depth of the rototiller—about ten to twelve inches,” he says.
When looking for a location, keep in mind how plants grow on their own. In general, partial sun is preferred. High shade? Even better, under tall trees, perhaps, or along a woodland’s edge where light is ﬁltered. Try rhododendrons in a border or as a hedge. For visual interest, Johnson mingles his with magnolias, crabapples, dogwoods, kalmia and azaleas (rhodies’ look-alike cousins). If space allows, a frame of evergreens around your rhododendrons is a great idea. Evergreens shield shrubs from damaging winter winds that can burn leaves.
Most common mistake? Overcrowding. To ensure a pretty picture that lasts and to foster air circulation for healthier results, consider what the plant’s height will be in ten years. Standards, for example, will be about ten feet; semi-dwarfs reach two to four feet; and dwarfs chime in around a foot and a half, just right for rock gardens.
Home Care l Lots of compost around the roots makes fertilizing unnecessary. If Johnson fertilizes (with Miracid), it’s a very rare occasion. But newly planted rhododendrons do require regular watering. For the ﬁrst year, ﬁgure twice a week. That said, make sure there’s adequate drainage. Overwatering is certain death.
Mulch (Johnson prefers a dressing of slow-to-decompose hemlock applied spring and fall) will keep weeds down and beds looking spiffy, as will deadheading, removing the spent blossoms or “trusses.” This chore, however, isn’t mandatory. “I’m a little obsessive for cosmetic reasons. There’s an old rumor that if you don’t deadhead, the plant produces fewer blooms. It may not be factual, but it’s justiﬁcation for doing something with them every day,” Johnson admits.
As for pruning, rhododendrons generally don’t need that either. “If you have to prune frequently, the plant shouldn’t be in that spot,” says Dr. Susan Gordon, who oversees the Kinney Azalea Garden in Kingston. Still, if they’re elbowing the house and there’s no recourse, use a clean, sharp tool and cut just before a node at the base of a leaf or bud. Bigger branches may require a saw. Flower buds form in early summer. “Get your pruning done by mid-June if you want to save flowers for next year,” Gordon advises.
Alas, rhododendrons are susceptible to a number of problems, scorched foliage and root rot being among the most common. Correct planting and mulching is the best prevention.