Starting Annual Seeds

Warm Soil

With a very few exceptions, annual seeds germinate best when the soil temperature is 70F.

This doesn’t mean the house temperature is 70F – because soil temperatures are typically 10F colder than air temperatures. This happens because water evaporation from the soil cools it down. Soil temperatures are cooler than air temperatures.

I accomplish this soil temperature by using a heating mat that automatically warms the flats sitting on it.

There are lots of suggestions for getting this soil temperature.

Put the flats on top of the frig where the warmer air (warm air rises) will help keep the flat warm. (this is uneven at the best of times).
Put the flats over a heat register to get warm air blowing on them (this dries them out really fast).
Use a heating pad. (This is a bad idea! – water from flats and fabric with electricity running through it is a bad combination.)
Wait until the air warms up naturally before sowing seed. (This works but some plants will not flower in anything less than tropical climates unless started very early indoors)

If you’re starting more than a few seeds, you’ll find the savings in buying starter flats to more than pay for the low cost of a heating mat.

Mini Greenhouse from Aquarium

Even Moisture

It is useful to keep the moisture level around the seed constant – and damp. A seed doesn’t need to be “wet”, it just requires “dampness” to initiate germination.

You can do this by using a wet soil and covering the seed to keep the moisture levels high around the seed. This works nicely.

You can cover the seed with soil. Do not bury the seed deeply but barely cover the seed with soil or a substance such as vermiculite. When I say “barely”, I mean so you can almost see the seed under the extremely thin layer of soil. Deep soil planting equals death to many seeds when starting indoors.

You can sow the seed on the surface and cover with a mini-greenhouse – using plastic or some clear film to hold in the moisture. The old-tyme gardeners used to sow and cover with burlap to keep the soil moisture high. The only problem with not covering with soil is that sometimes the young emerging roots don’t know which way to turn and you wind up with somewhat deformed seedlings. This is particularly true of larger seeds.

I recommend barely covering seed with starter soil.

And when you water – always use luke warm water to keep the soil temperatures high.

I note that cool soil temperatures and overcrowded seedlings are one cause of damping off where the seedlings suddenly keel over and die.So keep the soil barely damp with warm water.

Soil To Use

I use an artificial soil mix. It is clean, weed-free and sterile. That’s what you need to start seeds (no sense importing garden soil and growing weeds or fungus that eats your seedlings)

That’s the story right there. Not magic soil – not super soil – not garden soil. Use artificial soil (the peat moss kind).

Summary

That’s simple isn’t it.

Warm soil. Barely cover the annual seed with soil. Constant humidity but not swampy. Good soil.

And you’ll start annual seeds quite easily.

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