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Comment transplanter les semis à l'extérieur
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Whew! Your hard work and dedication has turned teeny-tiny seeds into thriving mini plants. But while there’s certainly now a reason to relax, a plant parent’s work is never really done. Your next mission is to set your seedlings up for success on the second part of their journey: Life outside. Transplanting seedlings isn’t as simple as just putting your little guys into the ground—but it isn’t complicated, either, with the right know-how. Here’s what to do.
Psst: Haven’t planted your seeds yet? Start here!
Avoid Transplant Shock and Damage
Once you experience the excitement of those first tiny stems sprouting up from the soil, it can be easy to get ahead of yourself and want to rush them outdoors. But it’s better to take clues from your plant kiddos and let them tell you when it’s time to transplant. Here are a few tips that can help you better understand seedling speak.
- Know the difference between cotyledons and leaves. Those thrilling first one or two leaves that appear? Sorry to burst your bubble, but they aren’t really leaves. They’re cotyledons, which are also known as embryonic or seed leaves. They’re thicker and harder than true leaves, which will grow later and resemble the foliage of a mature plant. You’ll want to wait until you have at least 3 or 4 true leaves before you consider transplanting.
- Work with your plant’s weather preferences. Understanding whether you’re growing cool-weather or warm-weather plants will help you determine when it’s time to start thinking about growing outside. For example, veggies like broccoli and kale can tolerate a light frost, while tomatoes and peppers need to be kept indoors until the threat of frost has passed. To determine when it’s safe to put your plants outside, check your local frost date. For either type, if any late-season storms or unpleasant weather is headed your way, hold off until it’s passed
Upgrade Their Space
If you sowed your seeds a little early (it’s easy to get excited!), or unexpected weather is keeping them inside longer than expected, consider giving your seedlings more space to spread out before transplanting them to their final destination. You’ll know they’re ready if their cotyledons are turning yellow, they’ve already grown 1 or 2 sets of true leaves, or their roots are growing through the drainage hole in their seed tray.
It’s easy to upgrade their abode: Clean yogurt containers, paper coffee cups, tin cans—anything you can add a drainage hole to—is fair game. Begin by filling the containers with Miracle-Gro® Seed Starting Potting Mix, which helps encourage fast root development. Use your finger or a pen to poke a hole into the center of the pot. If the soil is dry in their current home, water your seedlings before moving them. Then, carefully lift your seedling by the stem, not the leaves, and try to retain as much of the roots and surrounding soil as possible. Separate any tangled plants gently—after all, these are your plant babies. Settle each one into their pot, just deep enough that the plant remains upright, and smooth over the soil. Water lightly, and exhale. They made it.
Fix Leggy Seedlings
If your seedlings look spindly and scrawny, it’s best to address it before moving them outside, where they may struggle to withstand the elements. Leggy seedlings can be caused by a number of factors, including not enough light, too much or not enough water, or too much heat. Try to pinpoint the cause(s) now, while they’re still indoors, by experimenting with more or less of these factors, and see if that helps. If all else fails, you can bury up to two-thirds of the stems at transplant time to make them sturdier.
Harden Off Your Plants
Once you’ve gotten your seedlings in tip-top shape and the weather looks favorable, it’s time to start the process of hardening off. This involves gradually exposing plants to outdoor conditions to reduce the risk of transplant shock. They’ll start creating firmer plant tissue, which they’ll need in order to grow in a world of rain, wind, and hot sun. Trust us, your plant babies are going to be OK!
So, how do you harden off seedlings? Follow these steps and before you know it, they’ll be ready to graduate to the garden plot.
One to 2 weeks before you want to plant them in their permanent homes, start bringing them outdoors to acclimate. Begin by placing plants in a well-shaded spot for a couple of hours, then slowly build up the amount of sunlight and hours of outdoor time they receive each day. Be sure to bring them in each night. And use those plant parenting instincts—don’t put plants outside if temps are forecast to dip below 45°F, or strong winds or snow are expected.
Prepare The Soil
Prep your soil for its soon-to-be residents. Chances are, the earthy goodness you’re going to settle your seedlings into will need some help. For in-ground garden beds, make sure the soil isn’t compacted—use a rake or tiller to loosen it up if it is—and then mix 3 inches of Miracle-Gro® All Purpose Garden Soil into the top 6 inches of native soil improve the composition and nutrition.
If you’re reusing raised beds or containers from last year, renew the soil with Miracle-Gro® All Purpose Garden Soil or Miracle-Gro® Moisture Control® Potting Mix. Both provide up to three months’ worth of nutrition and can help plants produce twice the bounty versus unfed plants—and who doesn’t love that?
Finally, after weeks of growing, nurturing, and preparing, the big day is finally here. It’s time to transplant your seedlings! Try to transplant when it’s cloudy so plants don’t face a full day of direct sun right away.
For each plant, use a hand trowel to dig a hole just deep enough for the root ball to fit. Or, dig slightly deeper if you’re planning to partially bury any leggy stems. Either way, no shovel necessary! Use a ruler or tape measure for proper spacing (it’s also fine to eyeball it). Your seedlings will seem pretty far apart at first, but before you know it, they’ll be filling the entire plot with lush greenery, produce, or blooms.
Make sure the soil in their plugs or pots is moist before removing your seedlings. Then, gently pop the plants out by pushing on the hole in the bottom of the container with your finger, or use a butter knife or other tool if they’re stuck. Carefully place them in their new homes, cover their roots with soil, and water immediately. You did it!
Look After Your Transplants
First things first: Sit back, relax, and admire your accomplishment. Thanks to you, those tiny seeds you bought last winter are now full-fledged plants! And you gave them just the right amount of TLC they needed to make it safely outside. Now, your plant parent role transitions more into maintenance mode.
- Prepare for shock. Your plants may experience some level of transplant shock after transplanting. You prepared them the best you could, but it’s still a big transition! Transplant shock may involve wilting, yellowing, or curling of leaves. Keep plants well-watered and wait patiently. Within a few days, they should be back to their peppy selves.
- Continue to watch the weather. If temps suddenly dip, cover your plants with a large cloth—a bed sheet, drop cloth, or tarp will work—until the threat of damaging cold has passed. Support the covering with stakes to keep it from actually touching the plants.
- Water and feed. And of course, continue watering your plant babies and providing proper nutrition to help them reach their maximum potential. About a month after planting, start feeding plants an all-purpose plant food such as Miracle-Gro® Water Soluble All Purpose Plant Food, which delivers an instant boost of optimal micronutrients, according to label directions.
Your little seedlings have come a long way since winter—and so have you. Later this summer, you can enjoy the fruits of your labor (pun totally intended) and even try your hand at succession planting for more homegrown goodness. For now, congratulate yourself on a successful seedling transplant!