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December 28, 2014
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Diggin’ the seeds

Our seedling nursery was formerly set up in our dining room, as this picture from a previous year shows. However, giving that the set-up is in place from March through early June, we moved the seed-starting operation to a more convenient place. The seed-starting shelves are made from two-by-fours and fluorescent lights. The incubation arrays are reused every year to start many varieties of flowers and vegetables.
TRR photos by Anne Hart


In some years, the weather is warm enough in March that the fence around my garden can be inspected and repaired in anticipation of the upcoming gardening season. But this year, with snow still piled high, the garden gate has not even been opened yet, so garden activities thus far have been limited to starting seeds indoors.

The biggest challenge with starting seeds indoors is getting enough light to the seedlings once they emerge. A bright sunny window will sometimes do, but most windows aren’t sunny enough for a long enough time, and space in front of them is limited.

I met the challenge of light by building incubation shelves out of two-by-fours and other wood to make a series of four shelves, with two, four-foot fluorescent light fixtures that hold a total of four 40-watt tubes suspended over each shelf.

The height of the lights is adjustable, so the distance from the plants can be varied as the seedlings grow, and the lights can be maintained at about three or four inches above the tops of the plants. Plants grown under these conditions will still need to be hardened before going outside indefinitely, which means they will have to be introduced to the full strength of the sun somewhat gradually. But plants grown in this manner will be much healthier, bigger and more mature than plants grown with insufficient light.

The next major challenge with starting seeds indoors is heat. With heating and energy costs soaring over the past years, many people no longer heat their homes as warmly as in the past, and for some seeds that’s not a problem. Lettuce seeds, for instance, will easily germinate in temperatures as low as 50ºF. But many seeds are not so accommodating.

Tomato and pepper seeds, for instance, prefer soil temperatures in the range of 75ºF or higher to germinate. Seedling mats were created to raise the temperature of soil anywhere from 15ºF to 20ºF above the ambient temperature. Seedling mats are generally designed to accommodate two or four flats, which are the plastic trays that hold pots that hold the seedlings. A seedling mat placed under one flat will also provide heat to any flats that are located above the first flat, and so multiple flats can be heated with a single matt.

Another condition that needs to be controlled in seed starting is the amount of moisture in the potting soil or growing medium. Most seeds require moist soil to germinate but don’t like soil that is soggy. I use flats that have no holes in the bottom and can be filled with about half an inch of water. The water will be drawn up by the growing medium in the pots, which do have holes in the bottom.

This method of watering the seeds and seedlings from the bottom ensures that tender seedlings will not be jarred by pouring water from the top. Additionally, when seeds are first planted and seedlings are young, the flats may be covered with a clear plastic cap, which allows light to get to the seedlings, but keeps moisture from evaporating quickly; this reduces the amount of watering that is needed. These caps also hold warmth inside the flat.

Another element that needs attention in starting seeds is the potting soil or growing medium. There was a time when I bought the various ingredients myself and mixed them together in a wheelbarrow. I used a mix of about two parts peat moss, one part vermiculate and one part perlite, plus one part of compost from our compost pile.

I ultimately switched to pre-mixed starting medium for convenience sake; these products are quite good at ensuring germination. However, there are not a lot of nutrients in the mix, so a couple of weeks after most seeds have sprouted, they are transplanted into large pots, into a mixture of the prepared starting medium and compost.

Ultimately all of the seedlings will be planted in the garden. While my seedlings have been grown under fluorescent lights, most will still not be able to immediately withstand the strength of direct sunlight. The plants, therefore, must be gradually introduced to the sun—perhaps an hour on the first day, for instance, with increased exposure over the next four days or so, until they can be left out in the weather permanently.

In the case of my garden, the plants go from indoors, then into a greenhouse. After a few days inside, they can be planted directly out into the sun.

It’s important to read seed packets so as not to start the seeds too early. If you plant them too early, the plants will become too large and they will be stressed and won’t perform well. It’s also important to know when to put plants out in the garden. Some plants, like lettuce and snap dragons, can tolerate a frost and suffer no damage from a cold night. Other plants like tomatoes and sunflowers can be killed by a frost. It’s also helpful to know which plants are tolerant of transplanting, and which are not. Melons, squash, pumpkins and cucumbers do not like to have their roots disturbed, and often die after transplanting.

While seed starting may seem like a complicated process, it’s quite easy if you remember that seedlings and plants have certain requirements to thrive: they need the right amount of light, water, nutrients and space, and those variables can be rather easily controlled.

Once you’ve mastered seed starting, the variety of plants that can be grown is seemingly unlimited.