Very few flowering shrubs can equal the dazzling display that the Rhododendron family puts on in early spring. Wherever acidic soil and good drainage are found in zones 4 through 10, Rhododendrons can thrive, and delight the eye.
Azaleas are a sub-group of Rhododendrons and fortunately, a very winter hardy group of Azaleas has been developed by the University of Minnesota under the direction of Dr. Harold Pellet. Eleven named varieties of zone 4 hardy Azaleas make up the “Lights” azalea series – including Candy Lights, Golden Lights, Lemon Lights, Lilac Lights, Mandarin Lights, Northern Hi-Lights, Northern Lights, Orchid Lights, Rosy Lights and Tri-Lights. Many of these azalea selections have flower buds that have demonstrated winter hardiness to -40°F or even colder.
Other Rhododendrons that we have found doing well in Minnesota are Northern Starburst, PJM, and PJM Elite and Aglo. Lovely purple to lavender pink to hot pink blossoms almost entirely cover these tough and hardy Rhododendrons.
A key to having success with these excellent Rhododendrons and Azaleas is choosing a location that has good drainage and strongly acidic soil. The degree of soil acidity varies greatly in southern Minnesota, so you may want to research the native soil types present in your area, do a soil test, and/or create a nicely acidic soil.
You can create a good acidic soil by mixing top quality sphagnum peat with good quality topsoil and perhaps 10% sand to promote good drainage. I favor working sphagnum peat into the soil until you estimate that the planting area is almost 50% sphagnum peat. Perhaps you already have good natural acidity in your soil, but the addition of sphagnum peat will also help improve the organic matter content of the soil. It’s a winning strategy in any case.
If you want to enjoy eye-popping spring color in the years ahead, this may be the year you want to place some of these great winter hardy Azaleas and Rhododendrons in your landscape.