This species of Ravenea is from both the west and eastern sides of the Island of Madagascar. It was named after a river on the island. It is a large and elegant pinnate palm with heights reportedly up to one hundred feet. Trunk diameter is one foot. It grows at elevations from sea level to six thousand feet in both dry and moist native habitats. When younger, this species has flat erect leaves that go straight upwards. However, with age, this species produces leaves that are keeled and curve downwards at the ends. When mature the overall crown is hemispherical with the leaves in the upper portion of the circle. Because of its large size, this plant should be considered a major landscape item and not a companion plant. Photos below show how large this palm is when mature.
I have a limited number of five gallon plants on sale. They should be grown in an area where they can work their way from strong filtered light into full sun. Cold hardiness is into the mid-twenties F. They like moisture but need good draining soil. My thanks to TS at RPS for the photos below.