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Dig In: Tips for growing strong seedlings

To begin with I use the smallest packs of plastic cells that fit into these trays.
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Water seedling trays from below. (Mary Lowther photo)

By Mary Lowther

Here’s how I grow seedlings. Cut a piece of thick plastic with no holes, big enough to lay in a plastic tray that seedling flats come in. Make sure the plastic you cut comes over the edge because it must hold water. Nestle another plastic tray in this and snug them up together. Now when seedling pots sit in them they won’t leak.

To begin with I use the smallest packs of plastic cells that fit into these trays. I’ve tried newspaper rounds, soil blocks, peat pots, egg cartons, Styrofoam cups, milk cartons and margarine tubs and none of them work nearly as well as these thin-walled plastic cells that come joined together. They drain well, are light and easy to use, they’re cheap and they last for years. When a seedling outgrows the cell I either transplant it into the garden or into a larger pot. These small cells don’t use much potting soil either so if a seed doesn’t germinate there’s only a small bit of soil to toss.

Once you’ve got the flats filled and have placed the seeds on the soil, gently press the seeds into the soil to restore capillarity so water will rise up to keep the seeds moist when you water from below. I sow three or more seeds per cell and clip off all but one once they’ve got two leaves so that the strongest ones are left. Lightly cover the seeds with more potting soil or sand or pre-moistened coir. You’re going to water from below so this top layer will never become hard and will not prevent the seeds from sprouting through.

Since the soil is already moist you only ever need to water from the bottom — just pour in an inch or so of water into the bottom of the flat and place the flat under the lights. Don’t water seedlings with cold water as it could set them back and encourage damping off. Instead, fill a watering can with water and let it sit for a day or so, allowing the water to warm up to room temperature. I add one tablespoon of liquid fish fertilizer per gallon of water as this encourages growth.

I cover each flat with enough Reemay (spun cloth cover) to tuck under the edges and keep out predators. I cut this cloth large enough to accommodate the seedlings as they grow but I think it might be easier in the long run if I draped fine netting around the whole seed table — something to work on.

As the seedlings grow, keep raising the lights so they are always two inches above the tops of the plants. If their roots fill up the pots before you are ready to transplant them into the garden, re-pot them into bigger pots. Tomatoes and brassicas benefit from being planted deeper as they’ll grow more roots along the buried stem. I also brush the plants lightly once they’re a couple of inches high as I’ve found this results in stockier plants. Now that spring has sprung you’ll be glad you’ve started your own plants as they’ll soon be growing delicious fresh vegetables in your garden.

Please contact mary_lowther@yahoo.ca with questions and suggestions since I need all the help I can get.