Whether it’s a flat of bedding plants from a garden center or seedlings started indoors, you don’t want the transition from pots to garden beds to induce transplant shock.
The first rule of thumb is to watch where you put your thumb. Never pick up a seedling by the stem—it is the plant’s lifeline. Always handle seedlings by their leaves. Leaves will grow back.
Hardening off gradually introduces seedlings to the conditions in your garden. Bring all seedlings—store-bought and homegrown—outdoors and expose them to a steadily increasing amount of sun, wind, and temperatures lower or higher than what they were used to indoors. This will take about 2 weeks. Don’t rush it.
When to Plant
The ideal time to plant is when it’s overcast, with rain in the forecast and no frosts or heat waves expected. If conditions don’t cooperate, then try to plant in the late afternoon or early evening to minimize the time the seedlings bake in the sun. The day before planting, water the plants so that the soil in the pots is moist.
In the Ground
Keep your seedlings in the shade until you’re actually ready to plant each one. Don’t pull a plant out of its container until you’ve dug the hole for it. If you can’t easily pull it out of its container by the leaves, hold the pot in one hand, flip it upside down, and give it a sharp tap on the bottom. The rootball should slip out into your other hand. Snip away any damaged roots with scissors or pruners. If the roots are a solid mass, gently tease some away from the center, taking care not to break them.
Carefully slice into peat or newspaper pots with a knife to give the roots an escape hatch in case the pot doesn’t break down quickly. Once the pot is in the ground, tear off any part of it that extends above the soil line. It will dry out and pull moisture from the soil.
Plant the seedling at about the depth it was in the container, or a bit deeper. If your soil is cold or very wet, planting too deeply could rot the stem. An exception to this general rule of thumb is the tomato plant. You may want to plant tomatoes quite deep. Studies have shown that tomatoes planted up to their first set of true leaves set fruit earlier, and yielded more and larger tomatoes, than tomatoes planted at rootball level.
Firm up the soil around your seedlings, but don’t press so hard that you compact it. Give each seedling a thorough watering.
The First Days
Your seedlings have become established when you see healthy new growth. This can take a few days to a week, depending on the weather. Wilted leaves or drooping stems can be symptoms of transplant shock. Seedlings can go into transplant shock if they weren’t hardened off completely or if the weather is extreme. Most plants recover in a few days, but until they do: Check that the soil is firmly around the plants so that no air pockets are drying out the roots. Protect the transplants from sun and strong winds with row covers, sheets, or clothes. Water only if the top inch of the soil is dry. Don’t water if the soil is already wet; it won’t help.
Wait a week to 10 days after transplanting before fertilizing your seedlings. They will have sent out new feeder roots by then and will be entering their most active stage of growth.