Gardening Columns

These plants are acclimating to outdoor conditions
in the dappled sunlight beneath a big maple tree.

It's Time to Plant!

First published on garden.org on May 10, 2007, by Suzanne DeJohn

The coldest weather is behind us, and gardeners across most of our region can safely set transplants in the garden. Climate varies considerably over the region, however, so check with gardening neighbors if you're unsure when to plant. The average last frost date at high elevations is still weeks away! But for most of us, it's time to plant.

Preparing Seedlings for Planting
Whether you grew the seedlings yourself or purchased them, you'll need to prepare them for outdoor conditions. Plants grown indoors or in a greenhouse have been sheltered from direct sunlight, wind, and evening chills and are particularly vulnerable to transplant shock. Taking the time to prepare the plants will allow them to acclimate more quickly once they're in the garden.

Harden them off. Gradually expose seedlings to outdoor conditions over the course of a week or two. Start by placing them in a sheltered spot in dappled shade, and gradually move them to more exposed conditions. If your work schedule doesn't allow you to move your plants every few hours, try this: Put seedlings in a garden cart and place it in a spot where it will get morning sun and shade the rest of the day. After a few days, move the cart to where it will get a few hours of afternoon sun. Continue moving the cart, increasing the exposure to sunlight. Remember, though, that seedlings in small pots or peat pots may dry out in just hour or two of full sun.

Make sure roots are actively growing. If you remove the plant from its pot and see a mass of roots and little soil, the plant is pot-bound. This is especially common with seedlings grown in 6-packs. These plants have been subsisting on frequent fertilizer feedings and will have a hard time getting the moisture and nutrients they need from garden soil. I like to repot rootbound plants into slightly larger containers before hardening them off. Then I harden them off as usual. By the time they're ready to plant in the garden, I'll often see new, actively growing roots in the pot. (Young, healthy roots are usually white with lots of fine root hairs.)

Watch the forecast. The best planting time is a cloudy -- even drizzly -- day with cloudy weather predicted for the following few days.

Planting Time
Prepare the soil by loosening it and mixing in organic matter. Next, measure and mark the spots where you'll be placing the plants, following spacing guidelines. Although it's tempting to squeeze the plants a little closer together while planting, crowded plants may be stunted and are more susceptible to disease problems.

Dig a hole for your first transplant, making it slightly larger than the plant's rootball. Gently remove the plant from the container, remembering to hold it by the rootball or the leaves, not the stem. Place it in the planting hole and backfill, firming the soil gently as you go. Most plants should be set as deeply as they were growing in their containers. Tomatoes are an exception: Remove lower leaves and bury the stem up to the next set of leaves -- the plant will sprout roots along the buried stem.

Water and Mulch
Water seedlings at planting time and every few days if nature doesn't provide. Water slowly and deeply, rather than sprinkling the surface. Deep watering encourages deep roots, which are better able to tolerate drought. A soaker hose is ideal, since it keeps moisture off foliage, plus you don't have to stand there holding the hose.

Most plants benefit from a layer of organic mulch, such as pine straw, bark chips, or oat straw. Mulch conserves soil moisture, keeps clay soil from baking into an impenetrable surface, keeps soil cool, and helps prevent the spread of soilborne diseases. Keep mulch an inch or two away from plant stems.

Protect seedlings from sun and wind. Even hardened-off plants go through transplant shock when they're set in the garden. They're in a new environment and their roots have been disturbed. If post-transplant weather is sunny, warm, and/or windy, I scatter a thin layer of straw over the transplants to protect them.

Plan Ahead
Set up any supports you plan to use at planting time. Tomato cages are easy to place around small plants, but impossible to place over plants that are old enough to need them. If you're growing squash or cucumbers on a trellis, set it up now or you risk damaging plants and roots later.

Now you can relax, knowing your plants are off to the best start possible.