Starting Seeds Indoors

2016:  This is my 3rd year growing seeds indoors.  The first two years I followed the directions and used proper seed-starting mixes and had much better looking results.  This year, for unknown reasons (probably anxious to get started), I used regular potting soil to start a great many seeds.  The results were mixed: for most seeds, I had great germination, and great plants as a result. However, with slow-to-germinate seeds (in some cases), the results were not as good and in some cases downright miserable.  Algae and moss began to take over the surface of the soil, sometimes bubbling green ooze from the soil. This resulted in the top layer of soil being covered in muck - smothering these seeds and robbing them of light, water, and nutrients (my guess anyway).  Some seedlings that did emerge through the muck were struck with damp-off, killing the seedling. I am currently experimenting with hydrogen peroxide (2 tablespoons HP mixed in a hand-spritzer of water); I’m told this solution of HP and H2O will kill the algae and moss and not harm the delicate seedlings.  I’ll record these results in a later entry. I actually think there is a place for using regular potting soil for seed germination, but not for others. I’ll cover those here:

Seeds that can germinate perfectly well in regular potting soil:

• Pelargonium
• Only if done properly.  If you attempt it using the standard method, the result will be a green primordial stew of nastiness.  See Pelargonium entry for method.  
• Delphinium
• Germination is so easy and carefree.  Before planting, refrigerate seeds for 2 weeks.  Load up a tray of soil, scatter seeds across the surface, cover seeds with a good layer of soil (half an inch maybe), water thoroughly, place a humidity dome on top, and place in a cool dark place with no light for 2-3 weeks.  They like it cool, and they like it dark. No algae or moss grows in those conditions. Within 3 weeks, you have an entire tray full of seedlings (90% germination). Carefully introduce to light. Before using this method, I seriously struggled with these plants.
• Lupine
• Hollyhock
• Foxglove
• Lavender
• Salvia
• Coleus
• Dusty Miller
• Pansies
• Lambs Ear

Seeds that REQUIRE a good seed-starting mix (if starting indoors):

• Petunias
• Begonias
• Impatiens
• Celosia
• Penstemon
• Astilbe
• Flax

Basically any seed with a long germination period or tiny seed, should be started with a sterile, low nutrient, water retaining, well draining mixture that will not promote algae and moss from forming.  It’s also very important to get the humidity dome off as soon as germination has completed (or transplant the germinated seeds immediately - recommended).

I’ve not experimented with it, but I have read that winter-sowing has an excellent success rate for some of the trickier perennials like astilbe & penstemon.  If I’m around next winter, I’ll give it a go and report the results in a different entry.