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If you’re here, you hopefully have a healthy-looking seedling and are looking for information on transplanting seedlings to either a bigger pot or in the ground.
Our prior article, Beginner’s Cheat-Sheet to Starting Vegetable Seeds in 6 Easy Steps, provided an easy step-by-step guide to germinating vegetable seeds. This article now focuses on the next step on what to do with your seedlings when they have outgrown their starter pot.
If you’re new to growing vegetables, don’t worry. I was also new at one point and was skeptical about my abilities to keep plants alive. I thought I had a black thumb, based on prior experiences of dying houseplants.
Thus, I worried I’d similarly kill seedlings, whom I viewed as delicate creatures that could easily die if I mishandled them. Although seedlings are delicate, getting them to thrive isn’t rocket science. People have been growing vegetables for thousands of years now.
So long as you provide plants their basic needs, they will grow. With this guide, you should be able to master the next step of transplanting seedlings.
Why You Should Transplant Seedlings
If you used a seedling starter tray or other small containers to sow your seeds, then you need to transplant your seedlings into a bigger pot at some point. Ditto for if you bought pre-grown seedlings from a nursery that came in a small pot.
Eventually, roots will outgrow their initial container and require more soil depth and space. Otherwise, if you keep seedlings in containers that are too small, the roots will start to ball together, which impairs the plant’s ability to access sufficient nutrients from the soil.
Also, if a plant can’t sufficiently spread its roots to access more soil nutrients, the rest of the plant’s growth is stunted. You won’t get large, strong vegetable plants in this case.
When You Should Consider Transplanting Seedlings
Whether it’s time for transplanting seedlings depends on several factors. One is how much soil space and depth their current container gives versus the spread of a seedling’s roots.
If the roots have balled around the soil (i.e. the roots hold the soil together in a fairly clean clump if lifted out of the container), then you are ready to transplant. Also, if roots are coming out of the drain holes, then your seedling may be ready.
However, you also have to consider how large your seedling is. I wait until my seedlings are at least 2½ inches tall with a few sets of leaves before transplanting. Under no circumstance should you transplant a seedling before it gets its true leaves.
If you planted different types of seeds close together, and any particular seedling gets so tall that it blocks neighboring seedlings from getting adequate light, then you should also consider moving the bigger seedling. However, a seedling this big is likely beyond ready for transplanting at this point.
If your seedling shows signs of being ready to transplant, don’t delay transplanting for too long.
Where to Keep Your Transplanted Seedlings
I always prefer transplanting seedlings into slightly larger pots versus directly into the ground or garden bed at this stage, because seedlings are still young and vulnerable. Plus, they have been used to your indoor climate and will need to wean (i.e. harden) off of the indoors gradually if you plan to keep your vegetables outside ultimately.
Thus, depending on your outside environment and climate, nurturing your seedlings indoors longer would benefit them.
Keeping seedlings indoors allows you to keep an eye on water levels easier, and keeps the soil from drying out as quickly without outdoor elements like sunlight and wind.
Also, if you live somewhere that is very hot and arid in the summers/early fall, then starting your seeds and transplanting seedlings into indoor containers helps shield them from harsh outside elements until the weather is more hospitable outside.
Supplies You Will Need for Transplanting Seedlings
Here are supplies you’ll need for translating seedlings. You can click on the pictures or links for more information on each.
3½ to 4-inch pots are a good size. If you go with a larger pot, you need to keep a closer eye on water levels in the soil. Larger pots require more soil, which requires more water to keep the higher levels moist, where your seedling roots will start out.
Overwatering your plants risks root rot, so you need to ensure you water your plants enough, but not too much. Getting a pot with adequate drain holes can help.
However, even with drain holes, the soil in the bottom or middle of a large pot can stay moister than the top, so it may be harder for you to keep a good balance.
Thus, I don’t like to transplant small seedlings into a larger pot than they need right away.
Note: With root vegetables like carrots or radishes, then if you did not sow the seeds directly into the vegetable’s final resting spot (e.g. garden bed, ground, large container), then you should go ahead and do so at this stage. Root vegetables can be more sensitive to multiple transplants, so you should let the roots grow uninterrupted as much as possible.
Regardless of the vegetable type, if you plan to grow a vegetable in a container for its entire life cycle and want to transplant the small seedling into this final container now, just research the particular soil depth and spacing requirements to know how big of a container you need. At a very minimum, I’d suggest a pot that is at least 12 inches deep with a 10-inch circumference like this one. Cloth pots like these ones are also great, which I regularly use.
A general, organic potting mix is usually a safe bet when transplanting seedlings.
If you plan to ultimately do raised bed gardening, you should research whether you have a local bulk soil supplier, since buying bags of soil can get expensive. If you use regular soil, then you can mix equal parts peat moss, soil, and perlite. This mix should ensure proper soil aeration and draining.
For transplanting small seedlings, you won’t have to dig deep, but having a hand shovel/trowel is handy for transferring your soil into your pots. If you plan to stick with gardening and don’t have a good hand trowel yet, then now is a good time to get one.
Otherwise, since your seedlings are likely still rather small, you can get away with using a large kitchen spoon for now.
5 Easy Steps for Transplanting Seedlings
Best not to water seedlings before you transplant them. Dry soil is more likely to stay clumped together, which will facilitate transporting the seedlings roots and soil together.
Step 1: Prepare the Transplant Pot
Fill your next pot with your potting or soil mix. Try to gauge how deep your seedling’s root and soil clump will stand, and dig a hole large enough to accommodate your seedling’s soil clump.
Sometimes your seedling’s soil will come out in a nice, clean clump with the roots. Other times, the roots may not be tightly packed or even very deep at all. If the latter occurs, then you won’t need to dig a very deep hole.
You will want to line the final soil line up with the seedling’s current soil line.
Step 2: Remove the Seedling
Carefully remove the seedling from its current container. I always try to loosen the sides first be sliding a butter knife around the sides and then try to lift the soil up from the bottom with the knife.
Under no circumstance should you hold or pull on the seedling’s stem to try to get it out.
Step 3: Plant the Seedling
Place the seedling into the hole in your larger pot and fill the sides with soil, so that the seedling seems secure and straight.
The top of the soil should be level with where the seedling’s soil was prior to transplanting, not any higher or lower against the stem. However, it’s okay to put some soil on top of the surrounding transplanted soil to ensure it’s secure.
Step 4: Water the Seedling
Use a light stream of water to fully moisten the soil in your seedling’s new pot. If you use too heavy of a stream, you risk unearthing or knocking your seedling over. I just water until water comes out of the drain holes to indicate the soil is sufficiently moist.
Step 5: Provide Adequate Lighting and Water
If you keep your seedling indoors, ensure it has adequate lighting.
As discussed in our prior article, we hang full-spectrum LED lights over our seedlings with shop light mounts. The lights we use are T8, 6000 kelvin, 4-foot LED lights. T12 will also work. Or you can buy an assembled light stand like this one.
Your seedlings should remain 2-3 inches directly under the light at all times, so as they grow taller, you will probably have to adjust the lamp and/or seedling pot heights.
Water the seedlings whenever the soil appears dry at the top.
Next Steps: Maintenance and Hardening Off of Seedlings
If you plan to ultimately keep your vegetables outside, then you need to harden them off eventually. Hardening off is the process of preparing plants to withstand outside elements like sun, wind, rain, and temperature changes.
We discuss the process of hardening off in our next article, A Painless Guide to Hardening Off Seedlings: 4 Easy Steps. However, when you need to start hardening off your seedlings depends on the particular vegetable and your plant hardiness zone.
You need to time hardening off with your local frost schedule. For instance, in the spring, you wouldn’t want to transplant your plants outside until temperatures stay at least 45 degrees.
Also, the larger and stronger your seedlings, the better. If you have any leggy seedlings, they likely won’t survive the outside elements. I generally wait until my seedling are about 3 inches before keeping them outside full-time. However, whether you can transplant them outside sooner depends on how harsh your outside climate is.
Obviously, if you plan to keep your vegetables inside for their entire life, you don’t need to worry about hardening off. Instead, you just have to ensure they have a sufficiently large container and get adequate water, fertilizer, and light.
For outdoor vegetables, if you are ready to harden off your seedlings, then we will see you at our next article.
If you have any questions, comments, or tips about transplanting seedlings, please let us know below.