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Rhododendrons: bursts of bloom

A perennial favourite, rhododendrons give multi-season structure and vibrant colour to any garden

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A perennial favourite, rhododendrons give multi-season structure and vibrant colour to any garden.

Rhododendrons can grow and thrive almost anywhere in the world—from the tropics to the Himalayas. These hardy, versatile shrubs have been around since the dinosaurs, over 100 million years ago. They outlived those beasts and even survived the ice age 10,000 years ago. Chances are you can successfully grow them in your yard.

Atlantic Canada has native rhododendron species that still grow in the wild: Rhododendron lapponicum (an alpine dwarf) and Rhododendron canadense (the bog azalea). There is often confusion over the difference between rhododendrons and azaleas. Each has specific traits: true rhododendrons have 10 or more stamens, which is two per lobe; azaleas generally have five stamens or one per lobe. For the home gardener, it is enough to know that all azaleas are rhododendrons but not all rhododendrons are azaleas.

To grow rhododendrons successfully in your garden, you must choose a good location. Rhododendrons do not like wet feet and need at least half a day of full sun, preferably morning. They cannot tolerate a windy, exposed site nor do they like the dry soil under roof overhangs. A member of the blueberry family, rhododendrons need acidic soil to grow and perform well.

You will only need to spend 20 minutes each spring maintaining your beautiful plants.

Once you have picked your spot, dig a hole 30 centimetres deep and fill it with water. If the hole doesn’t drain within 15 to 20 minutes, abandon the spot and keep looking until you find one with better drainage.

Rhododendrons are understorey plants, meaning they like the protection of taller trees—especially evergreens. However, in order to flower profusely, they do need sun—but not glaring, midday sun. Most of these shrubs are broad-leaf evergreens that retain their leaves year-round, so they need protection from drying winter winds. Broad leaves have more surface area than needle leaves and dry out quickly.

If you have a dry autumn, give your rhododendrons a generous watering before the ground freezes. You can also protect them with several layers of burlap (not plastic), though this defeats their four-season attractiveness. Come spring, pick off any curled brown leaves.

With their preference for acidic soils and moist climates, rhododendrons thrive across Atlantic Canada and come in a range of colours and bloom sizes. Photo: Terra Ciolfe

Make sure your soil is moist and acidic—don’t guess (unless there are blueberries growing in the same spot). Fortunately, many areas in Atlantic Canada are naturally acidic. Pick up an inexpensive pH test at your local nursery or garden shop. If your location meets all requirements except a pH of six or lower, there are ways you can correct the soil. Add peat moss, mature compost, pine needles or fertilizer specific to rhododendrons.

The next step is to visit the nursery and pick out a healthy rhododendron for your yard. Choose one that will fit your space. Relatively pest and disease free, rhododendrons come in all sizes, from 15-centimetre dwarfs to seven-metre giants with corresponding spreads. Choose one that will fit your space when it’s mature.

While it may be tempting to purchase it in full bloom, the plant will do better and the blooms will last longer if you choose one with healthy buds and dark-green leaves with no signs of damage. The shrub’s shape should be uniform and well branched, not lopsided.

Once home, water the plant well and then dig your hole. Dig twice as wide as the container and to the same depth, so the soil at the top of the container is even with the surrounding soil. Refill the hole with a mixture of soil and mature compost. Water the plant again, unless it has rained recently and the soil is moist. Rhododendrons have shallow roots and you must not disturb the soil beneath them. Finish the planting by mulching with mature compost, pine needles, leaf mould or bark.

If you follow this advice, you will only need to spend 20 minutes each spring maintaining your beautiful plants. Simply hand weed to protect the roots and add a new layer of mulch 20 centimetres away from the trunk. Cut out any dead branches as close to the live wood as possible and pick off any brown leaves.

An interesting fact about rhododendrons is that they are thermotropic— sensitive to temperature changes and respond with leaf movement. When the air temperature drops below 2°C, the leaves will begin curling and drooping. The colder it gets, the tighter the curl, until the leaves resemble cigars. Researchers believe this protects the leaf surface from too much wind and sun exposure.

Rhododendrons generally do not require pruning. If you need to rejuvenate an older shrub, cut one-third of the bush back to the base of the plant. Do this in the spring for three years and your plant will revive.

While we often think of rhododendrons as June flowering shrubs, there are varieties that bloom in May and in mid July. The blossoms come in a range of colours: white, pale pink, deep pink, red, purple, orange and the coveted yellow. Blossoms come in various sizes, too, so be sure to check out the possibilities.

We are fortunate in Atlantic Canada to have some talented rhododendron developers. George Swain and Donald Craig of the Kentville Research Station in Kentville, Nova Scotia ran a rhododendron and azalea breeding program from 1952 to 1983. They developed shrubs specifically for our area. You can see the results of their program at the Kentville Research Station on Rhododendron Sunday each year in June.

Captain Richard Steele of Bayport, N.S. was a premier breeder of rhododendrons and magnolias in Nova Scotia for decades until his death in 2010. His hybrids are renowned throughout North America for withstanding the harsh growing climate of Atlantic Canada. You can find his shrubs at the Bayport Plant Farm near Lunenburg.

If you are looking for easy care, eye-catching shrubs to enliven your yard, rhododendrons are worth exploring. Available in numerous colours and sizes, they can be an elegant addition to your outdoor space that you will enjoy for years to come.

East Coast Living