|'Marathon' is a deciduous cultivar with a semi-erect habit, and bears an abundance of showy, vivid, magenta flowers beginning in mid-April. The 'P.J.M.' group of rhododendrons are smaller, growing to a height of 3 to 6 feet tall. Form is rounded and foliage is leathery and dark green until fall when it turns almost purplish. One of the reasons the 'P.J.M.' group is such a heavy flowerer is that the plant does not set seed. An excellent rhododendron for the New England states.
This rhododendron is the result of a cross between R. mucronulatum 'Cornell Pink' and another 'P.J.M.' hybrid. It was first developed by the Weston Nurseries in Hopkinton, Massachusetts.