Q. What is the best way to plant a rhododendron?
A. When planting rhododendrons, it is important to select a variety that is winter hardy for your plant hardiness zone, based on the USDA plant hardiness zone map. The Chicago region is zoned 5a and 5b. Rhododendrons should be planted in well-drained, acidic soil amended with large amounts of organic matter. A soil pH of 6 or greater, which is very common for the Chicago area, will need to be acidified by adding sulfur annually. No sulfur should be added to the soil until the pH is determined using a pH test kit or receiving a lab soil analysis.
Water the plant thoroughly before planting. Rhododendrons need to be planted high in a hole approximately one half the depth of the rootball because they are shallow-rooted plants and very susceptible to root rot. The top portion of the rootball should be covered with an acidic mulch such as pine bark to help lower the pH of the soil. The plants should be watered well after planting and mulch replenished yearly, if necessary.