Transplanting

You’ve grown or purchased the strongest seedlings you can find and can’t wait to get them in the ground. Sitting there in their flat, they’re so clearly healthy and vibrant, ready to produce all your heart desires. But the next step seems daunting. How do you transplant them so they… you know, live? Even better, are there some green thumb secrets to getting them in the ground so that they don’t just survive but thrive?

At some point, every gardener has to transplant their precious seedlings. Luckily, there are some tips and secrets that make for an easy process and plants that flourish, content in their new homes.

It helps tremendously to view the process from the plant’s perspective.

A Vulnerable Time for a Plant

Transplanting is the most vulnerable time for a plant. It can be an incredibly stressful experience for them, leaving them stunted or in seeming suspended animation for weeks afterward. Or it can be done so well that they barely seem to notice, even bursting forth in a spurt of growth afterward. It all depends on if the soil temperature is right, whether you’ve hardened them off, how much you damage their roots, planting them well, and if you give them a little boost.

Knowing the Secrets

Warm Enough Soil

First, wait until the soil is warm enough. Onions can be transplanted about as early as you can get into the garden to work the soil. Cool-season plants, like the cabbage family, are ready when the nights are regularly above 40 degrees. While a few nights of light frost won’t kill them, as seedlings, they are still quite tender compared to their adult forms. For warm-season plants, like peppers, tomatoes, and cucurbits, wait until a couple of weeks after your last frost date. 

Harden Them Off

Seedlings that have been grown indoors need a little time to get acclimated to direct sunlight and wind. Give them several days of increasing exposure to both. The following blog post explains the process, and some alternate options, in detail.

Hardening Off Seedlings

Be Gentle with Their Roots

Second, it’s very important to be extra careful with your plants’ roots while transplanting. By far, the best way you can protect them is to keep the rootball (the roots and all the soil around the roots) as intact as possible during the whole process. 

To get the plant out of the pot (or tray) without disturbing the rootball, grab the top of the pot so that the seedling sticks up between your middle and ring fingers and the top lip of the pot rests against your palm and closed fingers.

Invert the pot and gently bang on the bottom with the heel of your other hand. With planting trays, you can also gently squeeze the bottom tip of the soft plastic to help release the rootball. The rootball should fall out into your hand without disturbing the soil or roots. If not, turn the pot back over and carefully pull the soil away from the edge around the circumference of the pot with your finger and thumb, or even with a butter knife or the like in extreme cases, and redo the inversion and bottom banging process. 

If there are a lot of roots encircling the outside of the rootball, gently unfurl them so the plant doesn’t become root-bound (choked and impeded as they grow ever larger in this balled-up, smothering pattern) and, instead, can grow freely out into the soil. For most plants (with notable exceptions like melons), it doesn’t seem to hurt the plant nearly as much if a few of these outer roots are injured or broken, as long as the rest the rootball is kept intact. Still, being gentle and careful is rewarded. Also, if your seedlings were especially root-bound, it’s a sign they were in their pots too long. Make note, and start them from seed a little later next year.

Also, be sure to get the rootball in the ground as soon as possible after releasing it. If roots dry, they die, and the roots on the outside of the ball will dry out very quickly in dry spring winds, seriously injuring or killing the plant as it loses this first line of intrepid explorers that dive into the fertile soil of the planting bed spreading out looking for nutrients.

Planting Them Well

Depth

As for planting depth, for those familiar with transplanting trees or shrubs, you know it’s important to match your planting depth to the exact height it was in its previous medium. For garden plants, however, it’s fine for most, and often better, if they’re planted a little bit deeper than they were while in growing in pots or flats. Some plants, like tomatoes, can actually be planted quite a bit deeper, as they’ll sprout roots on any part of their stems put underground. Many gardeners take advantage of this characteristic of tomatoes by planting them deeply, especially if they’ve gotten particularly large or leggy while in pots or flats. Some gardeners, similarly, bury all of their seedlings up to their first true leaves upon transplanting, leaving the seed leaves (cotyledons) completely under the soil. As long as they’re not any shallower than they were in their pots or flats nor any deeper than their first true leaves (except for tomatoes), either depth is fine. Just make sure they’re deep enough to stand on their own and not tip over so they don’t grow crooked, especially for cabbage family plants.

Watering and Adding Soil or Adding Soil and Watering

After placing the rootball in the hole, be sure to “water the plant in” well and firm the soil back around the rootball. One of my favorite methods in especially loose soil is to make a hole to the proper depth, insert the rootball, fill the hole with water, and pull or dump the loose soil dug from the hole back over the area, allowing it to work its way around the roots as the water soaks in.

Another good method is only slightly different. After placing the rootball into the hole, add enough soil back to the hole until it’s just shy of the top. Add water and let the soil sink in around the plants’ roots. This allows you to add a lot of water without it overflowing the hole. Then finish adding the soil back, gently firming it around the plants’ roots and adding more water as desired.

In both methods, you want to make sure the plants’ roots are surrounded by soil but not to firm the soil so hard as to unnecessarily compact it. Using water to gently work the soil around the rootball and exposed roots, and only slightly firming the soil with your hands, if at all, is the secret.

A Boost

If everything else is done well, watering your plants with a fish emulsion solution during transplanting or within the first week, gives them a little boost to make a burst in growth and get a head start on the growing season. Follow the directions on the fish emulsion container for the proper solution and application.