PJM Rhododendron is, according to horticulture experts, an incredibly easy rhododendron to care for. Like any plant, it is certainly easier to grow and care for if you know a little something about its culture, habit, and habitat.
To begin, the PJM Rhododendron is a hybrid. It is the result of a cross between Rhododendron carolinianum and Rhododendron dauricum var. sempervirens. It is named for Peter J. Mezitt, the founder of Weston Nurseries in Massachusetts, the nursery that performed the first hybridization. But Rhododendron 'P.J.M.' itself is not a single cultivar; rather, it is a group of hybrids that are a result of the hybridization. Most of the seedlings that result from the hybridization are similar, but there are some differences in growth habits. Common cultivars of the PJM Rhododendron include 'Elite,' 'Northern Starburst,' PJM Compact Form,' PJM Lavender,' and Regal.'
When it's fully grown, the PJM Rhododendron is compact with a neat, mounded appearance with dense foliage. Most of these plants, especially when they're used in a landscape, grow to heights of about four or six feet, but they can grow to be as high as ten feet tall with a width of about 2/3 of its height.
During the summer months, this plant has elliptical evergreen leaves that are an inch to two-and-a-half inches long. During the winter, those leaves transform into a deep mahogany-purple color. PJM Rhododendron shows its vivid, potent lavender-pink flowers in mid-April and is a reliable bloomer. Because it's a hybrid, most PJM rhododendrons don't seed.
A plant's "culture" refers to the conditions in which it experiences the best growth. For the PJM Rhododendron, that condition includes soil that is moist and cool. While it prefers acidic soil, it is more adaptable to varying soil conditions than most other rhododendrons. The soil should be well-drained and contain large amounts of organic matter. You should avoid planting this rhododendron in areas that are characterized as harsh, dry, or windswept.
As it grows, PJM Rhododendron prefers either partial shade exposure to full sun. It should not be placed where it will receive mostly shade throughout the day. It is perfect for USDA hardiness zone four, meaning that it prefers climates where the average annual minimum temperature is between -30 degrees Fahrenheit and -20 degrees Fahrenheit. It thrives anywhere from hardiness zone four to hardiness zone seven. Compared with other rhododendrons, PJM Rhododendron is extremely winter hardy.
PJM Rhododendrons are not susceptible to many diseases. They are, however, often overused in landscapes because of their ease of growth; their popularity may be objectionable to some. And while they are reliable bloomers, not everyone finds their vibrant color appealing.
They do occasionally fall prey to Rhododendron borers and phytophthora root rot. And in harsh situations, they may become desiccated, or dried out.
If you want to propagate PJM Rhododendron, you can do it by way of cuttings in the summer, fall, or winter.