Garden Transplanting: Expert Advice

Follow these four simple steps to garden transplanting. They will help your seedlings make a smooth transition from pot to garden.

| April/May 2007

Starting your seedlings indoors, or purchasing greenhouse-grown transplants from your local garden store, can give you a head start that will add weeks to your growing season. This practice can make or break a crop if you live where summers are short, or in a climate where midsummer heat leads to a melt-down of cool-natured plants.

Growing your own seedlings indoors is easy and fun because you can try vegetable varieties rarely offered at garden centers, and start them under pest-free conditions. But take some time to “harden off” transplants before setting them out in your garden.

1. Harden Off Plants

Plants adjust to small, gradual changes in their environment better than sudden shifts, which is what the hardening off process is all about. Just as you get burned when you bare your untanned skin to the sun, leaves of plants started indoors will develop pale, sunburned patches if they are suddenly exposed to too much sun. The story has a happier ending when you introduce seedlings to bright light and sheltered breezes gradually, over a period of one to three weeks. In response to more abundant light, the leaves and stems bulk up on chloro-plasts — the mighty green organelles that transform light and carbon dioxide into energy for the plant. Much of that energy is sent to the main stem, which suddenly needs to get tough enough to twist and bend without breaking when blasted by wind. You may not see much new growth while plants are hardening off. But don’t worry; they are busy growing and rearranging exactly the kinds of cells they will need to prosper once they are set free in the garden.

This period of adjustment can take place on your deck or patio, within a protected enclosure out in the garden, or a little of both. For example, you might begin by setting your seedlings outside in a sheltered spot for two hours one day, and four hours the next, gradually increasing light and air movement levels until the babes have made it through several days and nights in the outdoor world.

If you are away from home all day, put the plants in a location that will receive early morning sunlight and be shaded as the sun’s position changes late in the morning. Watch your seedlings closely for signs of drying out, and be ready to shift them to larger containers if you see roots sneaking out of the drainage holes. If frost is predicted, take the plants inside.

2. Prepare to Transplant

While your seedlings are hardening off, prepare the planting space by amending the soil with compost and mixing in an appropriate amount of your favorite organic fertilizer. Both additions energize the soil’s food web, so that seedlings slipped into planting holes will be met by a welcoming committee of root-friendly fungi, bacteria and water-soluble nutrients. Some plants form stronger alliances with soilborne microorganisms than others, but soil scientists think that all plants take up nutrients and resist diseases better when they have strong relationships with life-forms that flourish in the rhizosphere — the fertile real estate where root and soil come together. Mixing at least a handful of compost into the bottom of planting holes used for vegetable seedlings helps these partnerships fall into place quickly.

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