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Garden Experiences: Starting Seeds in a Container

Copyright © 1999, 2011 by David E. Ross

Note: The following applies to starting seeds in a flower pot. It is not appropriate when using a flat, pony pack, or other shallow container or for seeding directly in the ground.

One problem with starting new plants from seeds is the fungus that causes "damping off" or "sore shin". This disease primarily afflicts very young seedlings. Suddenly, a sprout topples over. At the soil level, the stem might even look as if a small bite was chewed away.

To combat it, many gardeners use a sterile planting mix. However, peat moss does not require sterilization. It is a natural inhibitor against fungus, including the fungus that causes damping off.

I have used the following method to start dill and basil in flower pots. I make a mix of half peat moss and half sand, enough to fill the pots. I set aside about ¼ of the mix. The rest I use to make my usual potting mix. I pack that usual mix into the bottom ¾ of each pot and then add most of the plain peat and sand mix on top. I scatter the seed on top of the peat and sand and then top with the remaining peat and sand mix.

After an initial watering from above — with special care to avoid disturbing the soil and seeds — all further watering is done from below. The flower pot is set into a saucer, and the saucer is filled with water. The usual warnings about not letting a flower pot stand in water apparently do not apply with this method (possibly because of the anti-fungus characteristic of the peat moss and the draining abilities of the mix).

Be very careful not to allow the mix to get too dry. When watered from the saucer below, an almost-dry mix will cause nutrients near the bottom of the pot to "wick" up to the top before the new seedling roots are ready for such richness.

The theories behind this is that:

A mix of peat and sand will absorb water readily, drain well without becoming soggy, and yet make moisture available to plant roots until the mix is almost dust-dry. Thus, roots won't drown; but new seedlings won't dehydrate.
Peat will prevent damping off. Compost and many nutrients promote fungus; the nutrients might also burn very new roots. Thus, the normal mix — containing both compost and nutrients — is beyond the reach of newly sprouted roots.
Seeds contain sufficient nutrients within themselves to allow the seedlings to start growing, at least long enough until the little roots grow down and reach the nutrients in the normal mix. By the time the roots reach the normal mix, the seedlings are reaching the stage of growth where damping off and nutrient burn should no longer be major concerns.

By the way, I use clay pots and saucers for starting seeds. Moisture evaporating from the clay cools the pot and the mix inside. In case the sun briefly shines on the pot, I do not worry about the young roots cooking, which would be a concern with a plastic pot.

20 February 1999
Updated 20 May 2011