North American Fruit Explorers mailing list at ibiblio

[Don Yellman <don.yellman@webformation.com>]

Jerry:

Germinating very fine seeds like petunias, geraniums, impatiens, portulaca 
etc. can be a challenge.  One where a small sniffle can bring disaster.  I 
usually work with a magnifying glass, but easy it's not.  I wonder if you  
could improve your procedure by using transparent plastic covers to maintain 
humidity at the surface.  I use plant trays with close-fitting clear plastic 
domes, which will hold 8-10 individual 4-in. pots.  It shouldn't make much 
difference what planting medium you use, so long as it is sterile to prevent 
damping off of tiny seedlings.  If you can't find plastic domes, plastic wrap 
might be a workable alternative.  But the domes or wrap should come off as 
soon as the seeds germinate to prevent overheating if they are on an electric 
mat.  I use 2 waterbed heaters in series with an ordinary 600W light dimmer 
switch, and aim for about 80 degrees F, as measured by a thermometer inside 
the dome.

If you are unsure of whether your planting medium is sterile, moisten it and 
give it a zap in the microwave.  I do this routinely with my 4-in. pots, 
giving each group of 4 pots 3 minutes to reach temperature.  You will see the 
steam begin to rise from the planting medium, but if the plastic pots start 
to melt and slump, that is too much.  This practice does add a somewhat 
time-consuming step to seed germination, but it completely eliminates damping 
off, which is caused by soil fungal organisms.  Let the soil cool down before 
spreading the seeds on the surface.  Tiny seeds ought to germinate even in 
pure vermiculite if it is moist and warm.  I think you might want to bump up 
your germination temperature a bit, and cover as suggested above to hold in 
the heat and retain surface moisture.

This may be an OT post, but hey.  Let's call it Petuniex.

Don Yellman, Great Falls, VA