Growing Rhododendron Seedlings
by George Woodard
1.Mix two parts of one quarter inch screened pinebark, one part coarse sphagnum, peat moss, and one part perlite. Soak this mix with water and put into a four inch pot. Fill to within one and half inches of the rim.
2. Soak milled sphagnum moss in water and put a half inch layer evenly over the previous mix but don't compact it. When finished, there should be one inch from the sphagnum surface to the top of the rim.
3.Sow the seeds evenly over the top of the milled sphagnum.
4.Spray the seeds with fungicide (Ortho multi-purpose fungicide or Captan will do).
5.Stretch saran wrap over the pot and hold down with a rubber band.
6.Put under a light at a temperature of between 65 and 80 degrees F. Use a flourescent shop light with a cool white bulb on one side and a warm white bulb on the other. Hang the light about 12" above the pots. Time the light to be on 16 hours a day.
7.At a temperature of 70 degrees, you should start to see sprouting in about 2 weeks. After another week, the cotyledons will start to form. By the end of the sixth week the true leaves will be showing.
8.All during the first eight weeks, be careful to check for mold growing in the pots. Sometimes there might be chaff from the seed pods mixed with the seeds. This will develop mold that can spread and kill your seedlings. I prefer to check my seedlings every day so that if a problem arises it can be handled immediately. If the mold does occur, spray lightly with one of the above mentioned fungicides.
9.Take the saran off when the seedlings have grown enough to touch it. Bottom water (set the pot into a container of water and let it soak the water up from the bottom). Remove the pot from the water, let drain and put it back under the lights. Let it sit for a week.
10.Now is the time to start fertilizing. Use one TEASPOON (even-not heaping) of Miracid to one gallon of water. Put this mix in a spray bottle and spray generously every day. Every fourth day, alternate watering with a high phosphorous fertilizer such as Miracle Grow quick start, diluted to one quarter strength.
Note: If the seedlings are still small, it is better to bottom water until the reach a sturdier size. Dunk only when you feel that the pots are starting to dry out. Don't keep them soaking wet constantly.
11.After about twelve weeks, the seedlings are ready to transplant. Their roots have grown down into the bark mixture and have become more sturdy.
12.Remove the seedlings from the pots by prying them up with a pencil. Hold onto a leaf and gently put upward pressure on the tiny plant, while using the pencil to dislodge the roots. Two 20"x 24"x3" deep flats fit nicely under one light fixture. Plant them no closer than on two inch centers. The transplant mix should be basically the same as the sowing mix, except the bark should be half inch screened. It is also a good idea to add a professional mix that has composted pine bark as a component. Wet the mix thoroughly after putting into flat.
13.Maintain your daily watch. If the leaves start to turn brown or you see fungus or mildew forming, spray with the fungicide. Make sure the flats stay moist but not sopping wet.
14.In May, after the threat of frost is past, move the flats outside, being careful to keep them out of direct sunlight. Being outside in the rain will do wonders for their growth. Fertilize once a week with Miracid or put a few granules of slow release fertilizer on them. Around mid summer the seedlings will be ready to transplant.
Note: This article appeared in recent Cape Cod and Eugene Chapter Newsletters.