April 21, 2018
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Sturdy transplants take practice, careful planning

By Reeser Manley

I can recall a time when the earliest harbinger of spring was the appearance in late March of the long folding table, the kind you see at potluck church suppers, against one wall of the dining room. By early April, it would be covered with trays of cell-packs planted to seeds of sweet peas and nasturtiums, onions and tomatoes, some yet to show signs of life, others sending tiny leaves toward the artificial sun just inches above them.

So began two months of indoor gardening, of watering, fertilizing, transplanting, adjusting lights, moving trays of seedlings to and from the porch, until finally the sturdy little transplants were set out into the garden beds. If someone asked why we went to all of this effort, considering the variety of transplants available from nearby garden centers, we gave the only possible answer: you either start gardening in March or go insane.

Busy lives have changed all of this in recent years. With little time for a home-based seedling nursery, we search out the garden-center transplants for our own garden, yet Marjorie and I both are setting up transplant-growing operations in our respective teaching jobs, showing others how to do it.

Experience sets the schedule if you have been growing your own transplants for years. Newcomers should rely on the seed catalogs for planning information. For example, seeds of onions and pepper need a long time to germinate, so the seed catalog will tell you to sow onion seeds indoors in late February or early March, peppers 8 weeks before transplanting outdoors. Producing sturdy tomato transplants, on the other hand, takes only five to six weeks.

Backward planning is the key. Identify the last frost date for your garden site and schedule the seed sowing based on the timing recommended by the seed catalog. Despite the incipient insanity, don’t start too early. The resulting pot-bound, leggy transplants will remain stunted after planting in the garden and produce poorly.

Keys to success

Seeds planted in cold, wet soils tend to germinate slowly, if at all. Reduce the germination time with bottom heat, maintaining a soil temperature between 65 and 70 degrees. Heating mats and soil thermometers are available from mail-order garden supply houses.

Use a sterile growing mix with a starter nutrient charge and a wetting agent. I recommend both Fafard 2 and Pro Mix. Wet the mix ahead of use to the moisture content of a wrung-out sponge.

Use new or sterilized 2- to 3-inch peat pots or cell packs with similar size cells.

Sow two to three seeds per pot or cell, planning to thin to the sturdiest seedling after the first set of true leaves develop.

Sow the seeds on the surface of the growing mix and cover with a thin layer of a fine-textured germinating mix such as Ready-Earth. Particles in the courser growing mix can impede germination when used to cover small seed.

Cover the pots or cell packs with a loose layer of clear plastic shrink wrap to maintain uniform moisture. Once the seeds have germinated, remove the cover and the bottom heat. Optimum growing temperatures, both in the air and soil, are 65 degrees during the day, 60 degrees at night.

Provide supplemental lighting with fluorescent tubes as soon as the seedlings emerge; window light alone is too low in both duration and intensity. Keep the lights on for 14 hours each day, maintaining the tubes 2- to 4-inches above the growing seedlings.

Water the pots gently and thoroughly on planting day, then as often as necessary to avoid excessive drying. Be careful, however, not to keep them too wet; let the surface of the soil dry between watering. When you do water, use a half-strength solution of water-soluble fertilizer to provide essential nutrients. Water from above to leach excess nutrients from the pot.

Before transplanting your seedlings to the garden, they must be hardened off with a slow transition to outdoor conditions. Begin by setting them outside (temperature above 45 degrees) in partial shade for 1 or two hours per day, gradually increasing both the light and the length of exposure over a two-week period.

Thinking about all of this, I realize that all that has really changed is the location of this seasonal ritual, to folding tables in our respective classrooms. We are both still gardening in March and, in my case, with enough tables to supply transplants to the new schoolyard garden and a few extras for … another garden, somewhere.

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