Great Rhododendrons (Rhododendron maximum) grow wild in scattered colonies across New York and New England as far as southwestern Maine, but it's found primarily in the Appalachians from Pennsylvania to northern Georgia. Beyond that it has been widely planted as an ornamental. Wherever there is sufficient moisture, these evergreen members of the heath family can form dense thickets generally reaching a height of 13 feet, but old bushes are capable of growing to a height of 30 or even 40 feet and a crown diameter of 12 feet, essentially becoming small trees. The main requirement is acidic soil with a high organic content.
The concave leaves are long and leathery and curve down to smooth edges that may curl under during dry or cold weather. Most of the leaves are clustered in whorls around the end of twigs and surround the showy, rose-pink to purple, sometimes white, flower clusters that open between March and August, depending on the local climate. Our ornamental version opens in late May here in the northern Finger Lakes region.
In the wild, rhododendron is an understory plant and does well in the shade of taller trees. Combine that factor with the shrub's dense, evergreen foliage and you can understand why it's difficult for smaller plants and wildflowers to grow underneath rhododendrons.
This species has a number of alternate common names including Late or Summer Rhododendron, Great, Bigleaf or Deertongue Laurel and Rosebay. It's the state flower of West Virginia. The name Mountain Laurel is reserved for its smaller relative, Kalmia latifolia.
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