rhododendron seed starting

[Gene Mirro]

Gordon, if van Dusen stored their seed in the freezer, it will be as good as the day they froze it.  If they stored it in the fridge, it might still give some germination.  If they stored it at room temperature, it will give very poor germination, if any.

See http://nargs.org/smf/index.php?topic=635.0 for my method of growing Epigaea repens.  I now grow Azaleas, Rhodies and Oxydendrum arboreum using exactly the same method.  It's very similar to Todd's method, except my mix is a lot "dirtier".  The plastic bags can be replaced by transparent propagation domes if you are using 10" x 20" flats.  I really like the 4" tall domes made by NGW, model number 726239: http://www.sunlightsupply.com/p-11762-ngw-propagation-domes.aspx .  Ignore the part number in the photo; it's a typo.

 The method with the plastic bags and fluorescents is so bulletproof that I am now growing almost everything that way.  I don't see any damping off using this method; I can't explain it.  But keep a close watch for fungus gnats.  For some interesting control methods, google "fungus gnats kill".

I like to start fertilizing with dilute soluble fertilizer as soon as a good stand of seedlings is up.  Make sure to water the fertilizer into the mix thoroughly with a gentle spray of water.  If you don't fertilize, the plants will grow very slowly.

For a very detailed description of growing Haberlea and Ramonda using this method, see here:  
http://www.srgc.net/forum/index.php?topic=71.msg722#msg722
See also http://nargs.org/images/stories/plants/Gentianopsis.pdf  and
http://nargs.org/nargswiki/tiki-index.php?page=Physoplexis-Phyteuma

[Peter George]

How does one sterilize peat moss? I'm serious.

[Jan Jeddeloh]

I sterilize peat pellets for fern spore sowing by putting them in a heat proof plastic container (like a plastic shoebox), pouring boiling water in, and slapping the lid on.  The steam seems to do a good job of sterilizing it.  When it's cool I peel back the plastic mesh and sow my spores. I imagine you could just pack moist peat moss into any heat proof container  and nuke it for several minutes until it's good and steamy.

I think it might work to sow rhododendron seeds onto peat pellets the same way.  When I pour the boiling water in I try to avoid pouring it directly onto the pellets since that can wash out the peat.

My favorite plastic boxes for this venture are the clear plastic accessory boxes from The Container Store.  They hold 9 pellets which is enough for me of anything.

Good luck.

Jan

[RickR]

Using boiling water pasteurizes, and has always been my choice if I need to do it.

But in view of your "I'm serious" comment, the medium's temperature must be raised above the boiling point to be considered sterile.  Using a pressure cooker, or in an oven in a covered but not sealed pan would be good methods. 

[externmed]

Just to make things a bit complicated: I had 2 identical  pots of Rhododendron maximum (supposedly from the one red (chimeric?) plant still lingering in the Appalachian Mountains.  One pot I placed under a bright fluorescent plant light at 67F, the other I temporarily forgot in an unlighted 62F room.  Got rapid complete germination in the unlighted pot and slower 20% germination in the warmer bright light plant.  Transferred the lighted plant to the unlighted room and got, eventually, good germination.
These were special fluorescents that are two are 3 times brighter and also warmer than standard bulbs.  I don't know if standard 40 watt 4 foot fluorescents would have seemingly yielded poorer germination as well.
Charles S  MA USA
(one seedling has reddish stems-so far)   

[RickR]

That's interesting and useful.

My thermometer, placed 6 inches under the lights with the plants reads about 5 degrees F warmer than not under the lights.

67F is which?

[Gene Mirro]

Externmed, where the pots in baggies or under propagation domes?  How close to the lights were the seeds?  Did you keep the potting mix moist in the pot under lights?  There are a lot of variables.  I get my best germination of Ericaceous plants by surface sowing, and with the top of the potting mix about six inches below my 40-watt cool white lamps, at a room temp of about 55F (the temp under the lights is around 60F).  The pots are fully enclosed in a sealed freezer bag.  When they germinate under the lights, they don't have a chance to stretch and weaken.

[externmed]

Hi Gene,
The two identical pots with the same surface sown seeds germinated better in the dark at 60F, than in the light at possibly 80F in a baggie. 
I was just guessing that 80F and bright light was too much for this Rhodendron; but I was surprised with near total germination in near darkness.  They warm seeds germinated at least 60% when I moved them to the dark room
I wouldn't have normally used the bright light, but I had had a recent failure with the standard fluorescents--so it just went under there.
I have a room that I keep at 42F for the winter; if I have the time and ambition, I'll hopefully start a lot of seed in there next fall.
Thanks for your comments and suggestions,
Charles S   

[Gene Mirro]

I haven't tried a 42F room, but I'll bet that fluorescents in a 42F room will be magical for germinating alpines, bulbs, etc.  But growth will be slow at that temp.  I suspect that would be a perfect setup for the European alpine Gentians.

[Hoy]

This was one of my firstsuccesses with rhodo seed: R suchuenense, about 20 years ago. I used soil from the spruce woodland nearby and didn't cover the seeds. Kept the pot in a semi cold greenhouse during the winter. Now the shrub is 3m tall and 4m wide.