Propagating with a Nearing Frame is an inexpensive way to build a large stock of rhododendrons for garden or sale. The basic design is simple and construction is easy.
1. Begin by making a 3 by 12 foot box out of 1x12 cedar or treated lumber. The frame above is my first with treated wood for the box. I was unsure if leaching chemicals would be a problem, but cuttings have rooted right up against the boards for three years. The bottom is covered with 1x6 cedar fence boards. It should be tight, but not watertight.
2. Frame in a lean-to so that the roof begins about 12 inches above the box (so the cover has clearance to open as shown above.) Cover the lean-to with any weatherproof material. I used 6-foot fence boards. Secure critical points with steel ties, since wind can exert considerable pressure on the frame. This one withstood our 87 mph storm in 2003.
3. Make a lid frame out of 1x4 cedar and cover it with clear plastic, top and bottom for insulation. Guy Nearing used two glass window sashes that opened separately, but they were heavy, breakable, and non-insulating.
4. Find a location that is close to electricity for the heating cables and optional lights. The opening of the frame must be oriented to true north (or south for our friends in New Zealand, Australia, and South Africa.) This is critical to keep direct sunlight off the cuttings. Set the completed frame so that about half of the box is below ground level. I put a 3-inch layer of sand under the frame to facilitate leveling and help with drainage.
Options: (See these options here.)
* Make a bank of Nearing Frames. Line them up to the roof of one reflects light into the next one.
* Paint the underside of the roof and insides of the triangles white to give more reflected light. Paint the outside of the roof if you are having a bank of Nearing Frames.
* Use translucent green Fiberglas for the roof.
* Add fluorescent or gro-lights and a timer.
* The heating cables and rooting medium are covered in Preparing the Frame.
For detailed plans, see David Leach's Rhododendrons of the World. For Guy Nearings original drawings and two-page patent application (1931), see the Summer, 2002 issue of the Journal of the American Rhododendron Society. (The patent has long since expired.)