ARS Seed Exchange - distributes a catalog every February. One can order seeds of species and crosses: ARS Seed Exchange, 7921 Deepwell Drive, Bethesda, MD 20817-1927 USA. (Via e-mail: ARSseed@gmail.com or follow link from http://www.rhododendron.org.) The Rhododendron Species Foundation (http://www.rhodygarden.org) usually distributes a seed catalog early in the year also.
Make your own crosses, keeping careful track of pollen and seed parent, and ensuring that there cannot be contamination from other unknown pollen sources.
DO NOT!!!!!! just go down to the Botanical Garden and collect some seed. The bees got there first, and so what you will get is some unknown cross probably of little value. Species will not be true and you will be doing the rhododendron community a major disservice if you distribute the resulting plants as though they were species.
Planting media:
I use peat (the ordinary Sunshine baled garden peat) and perlite in a 50-50 mix, sometimes maybe with a bit of extra perlite.
I sterilize the mixture. This probably isn't necessary as peat is supposed to have some natural properties that keep mold, etc. from growing. However my success rate went from 10% to 90% once I started sterilizing before planting.
To sterilize, forget about the oven or the microwave. Get a large pot, fill it half full of water and bring to a rolling boil. Put some of the peat-perlite mixture in, enough to make a thick soup and boil for a few minutes (if it is too thick it spatters). Dip it out and let it drain in some sort of strainer (I use a spaghetti strainer.)
Once the mixture cools enough to handle put it in a CLEAN pot. I use 4-inch square pots, but any smaller pot will be ok. Cover with food wrap or some such. The aim is to cover it up when it is still warm, before too many mold spores from the air contaminate it.
Planting:
Smooth off the surface of the planting mixture.
Sprinkle seeds sparsely on the surface. I tap them out of a small folded piece of paper. Ideally one wants seedlings evenly spaced and not too crowded. However one never knows how many will sprout. I end up using half of an ARS seed packet, saving the other half for a backup.
Mist the surface with water to dampen the seeds. Some people sprinkle a fine layer of sand or chicken grit on top, but I have never done this. Put a label in the pot!
Put the whole pot in a clear plastic freezer bag and seal with a twist tie.
Aftercare:
I put the pot in the basement, at a constant 60-65 degrees (16-18 degrees C) under lights for about 16 hours/day and leave it for 2-3 months until the seedlings are one or two inches high. Alternatively any warm place with lots of light, but not direct sunlight, should work.
If you don't sterilize the media, you will not be able to leave the bag sealed up so long, but will have to open it periodically, and may need a fungicide of some sort.
Some bottom heat is supposed to speed things up, though I have not used it for seedlings. Some people suggest putting the pot on top of the fridge which is usually somewhat warmer than average.
Transplanting:
When the seedlings are an inch or two high I separate them and transplant them individually into 3-inch pots again using 50-50 peat/perlite, sometimes soaked in a dilute solution of fertilizer, the kind advertised for transplanting seedlings. No need to sterilize this time.
These seedlings then stay in the basement under lights for a while, depending on the season, and then go into the greenhouse and eventually into larger pots and outside.
Fearing's Farm Nursery
