How and When to Transplant Seedlings: 6 Easy Steps to Transplanting Success

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When and How to Transplant Seedlings

Have you been nurturing seedlings indoors and wondering when and how to transplant them? 


This blog aims to clarify proper transplanting techniques and empower you to transplant your young plants successfully.

There are two major categories of annual vegetables in the northern and southern hemispheres: "cool-weather crops" and "warm-weather crops."


When to Transplant Seedlings Outside

Click and expand on the transplanting season that applies to you.

In the spring, transplant cool crops before warm ones. (See diagram above for guidance on cool and warm-weather crops.)


The optimal transplanting times for most cool-weather crops are in the early spring.


Transplanting early in the year increases time for you to harvest and enjoy cabbages and lettuces. So, take advantage of the rising but mild spring temperatures to plant crops like peas, spinach, broccoli, turnips, collards, and Brussel sprouts. 


In general, in the temperate zones, when your days consistently hit the 60s F (15.5 C) and your nights don't dip below 40F (4.4 C), it is an excellent time to transplant cool-weather crops like peas and leafy greens.  


Transplant when the weather is consistently above freezing and within the allowable germination temperature range of your plant. 


Most summer crops germinate at a temperature above 60F and most cool weather crops around 40F. 


In spring, even if your day time highs are above 60F, your nighttime lows may still be dipping below these preferred temperature ranges. So pay close attention to both your highs and lows.


As the daytime temperatures consistently rise to 70F (21 C), you can grow more popular summer crops like tomatoes and melons. Just note that the window for planting most cold-weather crops will close as it gets hotter. 


Here are a few examples of spring plants and the temperatures they can tolerate outside:


how and when to transplant seedlings


If you happen to live in the tropics or the desert, most of your veggies will be warm-weather types. The best time of day for transplanting in hot climates is in the early mornings.  


In the extreme north, think of transplanting during the warmest part of the day: in the afternoons.


If you live in the southern hemisphere, your seasons are the opposite of those of the northern latitudes. Your spring is the northern fall. But the principle holds the same: Transplant during the fall and spring.

Can You Transplant Too Early?

Yes, you can transplant seedlings too early. This happens when temperatures are not yet consistently above 60F (15.5 C) during the spring, and a sudden frost or snow comes in.  


These temperature fluctuations can happen in the early fall as well. Here is an Instagram post from a veteran garden coach who experienced freezing temperatures rise to the 90sF (32C) in one week.



how and when to transplant seedlings


In the spring, it can be beneficial to "harden" your seedlings in trays outdoors for 1-2 weeks before transplanting the seedlings into the garden beds. Hardening means placing your protected seedlings or seedling tray outdoors to get used to winds and changing temperatures.


In the fall, hardening is easier to do and can be done in a few days, since the weather is warmer outdoors, and snow is generally unexpected.    


If snow or hale is possible, use a cloche or light row cover to protect fragile baby plants.

How big should seedlings be before transplanting?

how and when to transplant seedlingsn

"The point at which to transplant seedlings is when they are 2 to 3 inches high in the seedling flat. Exceptions are noted in the Master Charts of (the book) HTGMV."

The Master Charts John mentions above are invaluable in planning, starting, and transplanting your seedlings at the right times of the year.

These charts have plant-specific data on yields and even the caloric value of the crops listed. The depth of garden information, among many other reasons, is why we recommend this book to our clients in our Grow-It-Yourself program.

Before you Transplant

1. Check Your Seedlings Status

  • As noted above, make sure that your seedling is about 2-3 inches high before transplanting.
  • We also recommend transplanting a seedling after its two "true leaves" first come out. True leaves are the leaves that grow after the initial seed's cotyledon leaves come out. Not all plants have prominent cotyledon leaves. So transplant after you see at least two sets of leaves (four leaves) grow.


how and when to transplant seedlingsn

"It's time to transplant seedlings when they have developed their second set of true leaves. This is a critical point in a seedling's life, because it has used up its stores of nutrients in the seed. To continue to grow, it requires outside fertilization, optimally from nutrients in garden soil. If the outside weather is not ideal for planting, then this is a good time to transplant the seedlings to a bigger pot with potting soil, which contains essential nutrients."

  • Harden your seedlings outside before your transplant them. Even just one day of hardening helps. As state above, 1-2 weeks in the spring or a 1 or more days in the fall is best practice.
  • If your seedlings become leggy (too long), that is a sign that they are outgrowing their current trays or pots and are longing for more soil to grow in. (It could also mean they are reaching for a light source.) If you cannot transplant outdoors due to temperature, transfer them into a larger tray or cell pot as soon as you can. Another word for this is "pricking." We recommend 4.5-inch deep square pots for "pricking" because they fit very nicely into the 1020 trays that we recommend for starting seeds.

how and when to transplant seedlings

2. Check Your Temperature / Weather

  • Transplant before, during, or after a rain event and take advantage of rain doing the watering for you. If rain is not in the cards, make sure to water the seedling tray and your garden bed heavily before you transplant.
  • Transplant during the cooler times of the day to avoid "transplant shock." This practice is a perfect example of "working with nature" and not against it. If you transplant during rainy weather, you don't need to worry about watering your plant!

2. Check Your Moon Phase

According to those who plant by the phases of the moon, the moon's "second quarter" (specifically, two days before the full moon) are the best times for transplanting crops that have their "seeds inside the fruit," such as beans, melons, peppers, squash, and tomatoes. These kinds of plants happen to be mostly summer crops. 


The Farmer's Almanac tells us that those crops we eat below ground, such as the roots and tubers of carrots, potatoes, and onions, grow better when transplanted during the "waxing of the moon," or after the full moon.  Biodynamic gardeners note that the moon's energetic action on plant growth below ground and above ground is in line with the moon's gravitational pull on the ocean tides' rising and falling. 


If you don't get this moon phase quite right, do not fret. The most important thing is that you actually transplant successfully during your seasonal windows of opportunity and do not let your seedlings die.

how and when to transplant seedlings

How to Transplant Seedlings

What you will need:

  • A"dibber" - A "dibber" or "dibble" is any "hole poker" that you can use to make indentations in the soil to accommodate the plants' root system.

  • Spade
  • A watering can filled with water or hose with a nozzle spray
  • Your seedlings


Note: If you are comfortable with it, you will be more successful transplanting seedlings using your bare hands. The roots of plants are fragile, and you'll need as much control as possible to ensure that they are kept intact in the process.  In the video below, Dave transplants using gloves because he had just suffered from a rash from poison sumac.

How to transplant

    • Using a dibber, make a hole in the soil deep enough so that one half of the plant and all of its roots are under the soil.

    • If your roots are long, make sure to not only make a hole but a shaft that goes down far enough so as not to compromise root growth during the transplant.
    • If your seedling comes in a biodegradable pouch that will break down and not impede root growth, make a hole large enough for the whole pouch. Use a space or shovel, as shown in the video. Doing this is an excellent way to keep "plant stress" at a minimum. Sometimes, these root pouches need to be broken up, and the roots freed and spread apart to help the plant grow optimally.

Steps to Successful Transplanting

    • Heavily water the area you have prepared for the plant.
    • Heavily water the plant or seedling tray before transplanting.
    • Hold your plant by the "ears" or two true leaves and retain as much of the original soil around its root system as possible when you transplant.
    • Gently transfer the plant into your hole.
    • Cover the transplant with a good mound of soil so that one half of the plant is below ground, and the other half is above.
    • Water again. 

Dig Deeper

Attend the How to Grow Food in Small Spaces Webinar!a free workshop on figuring out what to do garden-wise this coming month!

If it's the late summer or fall, consider learning more about Extending Your Vegetable Garden into the Fall.

If you've followed all the recommendations above and your transplant still dies, ask the following questions:

Get to the root cause. Pun intended. 

Never give up.  

Be tenacious. Experiment. Re-read this article. 

And please, try again.

Share this post with other growers!

Comments 8

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  1. Thank you for your information I’m interested in planting flowers and learning about how to prune them and transplanting.

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  2. Didn’t you mention something that can help young seedlings that you sprinkle on the roots? Some kind of granules? I’d love to know what that is?

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