With the gasoline and gunpowder gang’s biggest holiday of the year now upon us, wouldn’t it be nice to get away from the noise and the enduring adolescence for just a little while to see something spectacular that isn’t exploding or on fire? Well, here’s a suggestion: head for the hills to check out the flowers of our native rhododendron, the Great Rhododendron (Rhododendron maximum), also known as Rosebay.
Thickets composed of our native heathers/heaths (Ericaceae) including Great Rhododendron, Mountain Laurel, and Pinxter Flower (Rhododendron periclymenoides), particularly when growing in association with Eastern Hemlock and/or Eastern White Pine, provide critical winter shelter for forest wildlife. The flowers of native heathers/heaths attract bees and other pollinating insects and those of the deciduous Pinxter Flower, which blooms in May, are a favorite of butterflies and Ruby-throated Hummingbirds.
Forests with understories that include Great Rhododendrons do not respond well to logging. Although many Great Rhododendrons regenerate after cutting, the loss of consistent moisture levels in the soil due to the absence of a forest canopy during the sunny summertime can, over time, decimate an entire population of plants. In addition, few rhododendrons are produced by seed, even under optimal conditions. Great Rhododendron seeds and seedlings are very sensitive to the physical composition of forest substrate and its moisture content during both germination and growth. A lack of humus, the damp organic matter in soil, nullifies the chances of successful recolonization of a rhododendron understory by seed. In locations where moisture levels are adequate for their survival and regeneration after logging, impenetrable Great Rhododendron thickets will sometimes come to dominate a site. These monocultures can, at least in the short term, cause problems for foresters by interrupting the cycle of succession and excluding the reestablishment of native trees. In the case of forests harboring stands of Great Rhododendron, it can take a long time for a balanced ecological state to return following a disturbance as significant as logging.
In the lower Susquehanna region, the Great Rhododendron blooms from late June through the middle of July, much later than the ornamental rhododendrons and azaleas found in our gardens. Set against a backdrop of deep green foliage, the enormous clusters of white flowers are hard to miss.
In the Lower Susquehanna River Watershed, there are but a few remaining stands of Great Rhododendron. One of the most extensive populations is in the Ridge and Valley Province on the north side of Second Mountain along Swatara Creek near Ravine (just off Interstate 81) in Schuylkill County, Pennsylvania. Smaller groves are found in the Piedmont Province in the resort town of Mount Gretna in Lebanon County and in stream ravines along the lower river gorge at the Lancaster Conservancy’s Ferncliff and Wissler’s Run Preserves. Go have a look. You’ll be glad you did.