Mountain Laurel and Rhododendron: What are the Differences?

Mountain laurel, (Kalmia latifolia) Pennsylvania’s state flower, and rhododendron (Rhododendron linnaeus) look very similar and are often mistaken for each other. Although both belong to the heath family (Ericaceae), they are different plants that bloom during different months. Here are some ways to tell them apart, and some WPC preserves where you might find them both! 

Bloom Time

  • Mountain laurel typically blooms in late May, peaks in late May and early June, and fades by late June.
  • Rhododendron usually blooms in late June, peaks around July 4 to 10 and fades around early August.

FlowersMountain laurel and rhododendron flowers

  • Mountain laurel has pink and white, symmetrical, cup-shaped flowers that grow in clusters. It’s also known as a “regular” flower. If you draw imaginary lines across it through the center to create pie-shaped wedges, all wedges are identical.
  • Rhododendron usually has white, asymmetrical flowers with just a tinge of pink. It has green speckles.

Mountain laurel and rhododendron leavesLeaves

  • Mountain laurel has a shorter, glossier, lighter green, elliptical-shaped leaf.
  • Rhododendron has a longer, darker green, less glossy, elliptical-shaped leaf.

Preferred Habitat

  • Mountain laurel, as its name implies, prefers a sunnier, drier environment, such as on mountains.
  • Rhododendron grows in cool, very moist areas such as on the banks of streams.
  • However, you will sometimes find the two plants growing side by side.

WPC Preserves Where Both Plants Grow

Some Western Pennsylvania Conservancy preserves where you’re likely to find both mountain laurel and rhododendron include Bear Run Nature Reserve and Beaver Creek Natural Area, both in Fayette County, Dutch Hill Forest in Jefferson County, Bennett Branch Forest in Clearfield and Elk counties and Whites Creek Valley Natural Area in Somerset County.

Mountain Laurel Fun Facts

  • When the bud is closed, the anthers, which hold the pollen, are on stems that are tucked into little pockets and are under pressure. When the flower is fully opened and a bee comes to pollinate, the bee stumbles on the stem. It trips the stem like a spring, and the anther springs forward and shakes pollen onto the bee. You can spring the filament with a twig and see the pollen flying through the air.
  • Mountain laurel is Pennsylvania’s state flower but is not protected.
  • All parts of the mountain laurel plant and flower are considered toxic. 

Rhododendron Fun Factscurled rhododendron leaves

  • The black throated blue warbler, a small, insect-eating forest interior bird, is also known as the rhododendron warbler. The rhododendron creates part of the dense shrub habitat that warblers seek. Hikers can keep an eye, or ear, open for the birds during May through September in Western Pennsylvania, particularly at our Bear Run Nature Reserve.  
  • Rhododendron leaves will curl in the cold of winter when the temperature drops below about 28 degrees Fahrenheit.
  • Rhododendron, whose wood is rose colored, is used to make furniture, particularly in Europe.