For generations of gardeners, and certainly for me, Rhododendrons represent the arrival of spring in our local landscapes. Everywhere you drive this time of year there is a stunning Rhododendron in full bloom to catch your eye. These flowering beauties come in all sorts of shapes, sizes and colors, and thrive in our climate when located and planted correctly. The choices of cultivars is truly endless with over 5,000 registered varieties; some growing tall while others small and some blooming as early as February and others as late as June. While some may be hard to find hard, the “stock” varieties available at most local nurseries work beautifully, representing a good mix of useful old school flavors with some newer, more modern options. Pacific Rhododendron (R. macrophyllum) is our PNW native species, but other really cool species and hybrids with fun foliage and flowers can be found and grown successfully in our gardens as well.
Let us begin on the smaller side and consider some of the excellent dwarf varieties available. Rhododendrons don’t have to be the size of your garage or bury the garden with age as there are plenty of smaller growers are out there. Many gardeners mistake these for Azaleas as they have similar sized foliage, but most dwarf Rhododendrons are more sun tolerant, cold hardy, and perhaps even more durable than Azaleas. I have utilized many in my own garden in a sunny south-facing rockery, while others I have placed in locations with a little more afternoon shade. It is so nice to come home and see these in bloom right now - low growing little mounds full of color. If you look, you can find almost any flower color in a dwarf option, staying under 2 feet tall and spreading a little wider. Many other compact options, that will stay under 4 feet tall, are out there too and can be used as foundation plants or tidier specimens for smaller garden locations.
All Rhododendrons will thrive in a part sun/part shade woodland garden location, but deep shade and full afternoon sun are two extremes in which we need to be a little more careful with our choices. Many gardeners complain about their leggy/spindly old specimens, while others see their plants get sunburned every August in the heat. Often these plants were put in bad locations to begin with, and a different, better suited variety would thrive better in these same garden spots. While there is no steadfast rule to keep in mind, a couple generalizations will help when making your choices… Larger foliage typically means plant in part to full shade locations in the garden, while smaller leaves (like the dwarfs above) tolerate much more afternoon sun. The other factor is flower color, and again there are some exceptions, but generally reds, purples and some pinks will take more sun, while lighter pinks, yellows, oranges, and white prefer shade in the afternoon to look their best.
Rhododendrons are acid loving and should be planted using a good acidic compost as an amendment and some mulch over their roots (but not up onto their crowns). Feeding them a couple times a year will keep them look prime with lush green foliage and optimal annual growth. I always try to feed mine once in March or April with a good granular organic Rhododendron food, then repeat again in June to help over the summer. One great trick I picked up a few years back is using a product called Ultra Bloom from E.B. Stone Organics, in addition to regular Rhododendron food. This product is all about Phosphorous and Potassium and contains no Nitrogen – the perfect supplement to increase bud set and thus bloom count exponentially for the coming spring. I highly recommend using this to simply pump up your flower power, and as a bonus, it helps with many other plants in the garden too. Since Rhododendrons set their flower buds over the summer for the next season (they are “old wood bloomers”), adding Ultra Bloom in June will increase your bud count, just as it has for me in my own garden.
As all Rhododendrons are “old wood bloomers”, please follow my simple rule of “prune after bloom”. Because buds are set in summer, any summer/fall/winter/early spring pruning will cut buds off and reduce flowering the next spring. Right after they are done blooming is the perfect time to cut plants back to reduce size and then feed them. This will result in a superior, compact plant with maximum flower power the following spring. We should also consider the yearly chore of deadheading… To deadhead or not to deadhead? (A common question at the garden center, for sure.) My OCD side says yes, and I often do my shorter growing varieties, especially when they are young and manageable. Do I climb up and deadhead the 12 foot tall one in my front yard? Of course not! It is ultimately up to you, as this is not a necessary chore in the garden. I always bring this up when discussing pruning: remember that if you prune back a bit after bloom, you essentially get your deadheading done at the same time.
I was planning on listing out a hundred of my favorite cultivars, but in all honesty, everyone has different affinities for foliage and flower. If you simply explore your options you will find many suitable candidates for your specific garden tastes. Look for eye-catching foliage as well: some variegated options can be found, and indumentum on Yak type Rhododendrons (R. yakushimanum cvs.), adding interesting leaves for morning sun/shady gardens. I cannot resist mentioning some specific hybrids with excellent flowers that can be found now. A few newer introductions that offer unusual bloom colors are ‘Pomegranate Splash’ (fuchsia/white), ‘Seaview Sunset’ (orange/yellow), ‘Cherry Cheesecake’ (white/pink), ‘Neon’ (orange/yellow), ‘Hachmann’s Picobello’ (white/purple), ‘Honey Butter’ (yellow/orange), and ‘Melrose Flash’ (white/pink). Mix these with some great classic options like ‘Jean Marie’ (red), ‘Taurus’ (red), ‘Hotei’ (yellow), ‘Nancy Evans’ (yellow), ‘Calsap’ (white/purple), ‘Chinoides’ (white), ‘Anna Rose Whitney’ (pink), ‘Hachmann’s Polaris’ (purple), ‘Purple Splendour’ (purple) and ‘Cosmopolitan’ (pink) and you have yourself an outstanding spring flower show from March through May.
As we near the end of April and head into May, this is THE Rhododendron season. Visit your local garden center now to see them in bloom and take advantage of maximum selection. Speak with a Certified Professional Horticulturist about your particular needs and let them help you find the perfect plant for your landscape, not only for the color, but also for the ultimate size, desired foliage and growth habit. This weekend, on Saturday, April 27th, from 10am to 2pm, Sunnyside Nursery hosts their special annual Rhododendron Flower Truss Show. The Pilchuck Chapter of the American Rhododendron Society (our local club) runs this, and on display will be a plethora of cool flowers to drool over. These folks are the gurus in the world of Rhododendrons and they love to talk plants, along with share information and stories on all kinds of fascinating varieties. I encourage everyone to come by the nursery and enjoy the frivolities as we celebrate our state flower, the Rhododendron. The PNW has many to offer, and I am sure you will find a specimen that will bring you smiles every spring when it lights up your garden with some serious spring flower power.
