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How to Time the Transplant of Your Seedlings

Timing is everything when it comes to gardening, especially when to transplant seedlings. Knowing not only how, but the right day to move your baby plants from their cozy indoor setup to your garden is a big part of the indoor seed starting journey. That’s why in this post, we’ll explore the signs for you to look for when you’re ready for transplanting, share best practices to ensure you have fun while doing it, and offer tips to reduce transplant shock.

Marion Owen on the left with her winter beanie on and giving a gardening lesson, overlayed with a female gardener holding a tray of indoor started vegetables

Timing the Transplant

Before you head outside into the garden, make sure that you have timed your seedlings properly. In order to do this you will need to review the information found on the seed packet, and look up your frost date. Most resources will refer to the last frost date or frost free date as a reference point. All this can be confusing because frost free date is now a moving target, thanks to climate change and severe swings in weather patterns.

Where I live in Alaska, the official frost free date is May 16. Some plants will need to wait until after this date has passed, while hardier ones can often be planted before. 

What is the frost free date? This is when your region is known to be free from frost and safe to plant in your garden. Planting before this date could mean that you expose your seedlings to frost or temperatures that are too cold for it to thrive, impeding their development and maybe even killing them.

Let’s use kale as an example: Check the seed packet to see when to start the seeds. Kale seeds are typically started four to six weeks before the last frost date. This means you should start your seeds indoors about four to six weeks before the expected last frost date. Kale is quite hardy, which is why you can plant it in the ground (in cool climates) as early as April 1. Knowing how to time your seedlings can really help extend your growing season.

Signs Your Seedlings are Ready for Transplanting

Transplanting a seedling, whether it’s into a larger container or outside in the garden, is one of the most important (sometimes dangerous!) part of that seedling’s life. So what are the signs that it’s ready? When it has its first true leaves!

What are true leaves?

When a seedling first sprouts, they look very much the same. These are not the true leaves of the plant. True leaves are the second set of leaves that appear after the initial seedling leaves.

From one of Marion's gardening lessons of Youtube: Marion is holding a plastic tray lid which has 12 micro soil cubes and seedlings growing. She is pointing to one with a pencil, about to demonstrate how to thin the seedlings and transplant them to larger containers

Root development

When you’re transplanting the seedlings, make sure to check for strong root development. The stronger and healthier the roots are, the more likely they are to not only survive transplant, but thrive!

Pro tip: Root growth is a positive sign that your seedlings are ready. 

Watch this video about top tips for transplanting seedlings started indoors

Best Practices for Transplanting Seedlings

  1. Transplant when seedlings show true leaves.
    When your seedlings put out their first ‘true’ leaves (usually the second set), that’s your cue that they’re ready for a larger container.
  2. Prepare the new location.
    Make a planting hole slightly wider than and the same depth as the container. For cabbage-family crops bury their stems up to their first set of true leaves. For lettuce, not so deep. For tomatoes, bury most of the stem, leaving just the top leaves.
  3. Use a pencil or other narrow tool to avoid damaging the roots.
    That’s right! I love to use a pencil to tease out and lift up the roots, but anything similar, like a butter knife will do. Simply slide it along the roots and carefully lift it out. Then, what I do is I just make a little hole and press it in with the pencil and just press the soil around it. I recommend watching the video above for a visual on this process!
  4. Water seedlings well after transplanting.
    Carefully water the soil around the newly transplanted seedling well so that it can easily sink in.

Tips for Reducing Transplant Shock

Before you get too excited and make one of the most common mistakes beginner gardeners make when it comes to growing their own plants from seeds– take some time to head over to one of my other blog posts to read about hardening off!

Hardening off is the process used to help your seedlings adjust to their new environment and avoid transplant shock. It’s like traveling from a place like Kodiak, Alaska to the tropics – you might get a little sunburned! To give your seedlings the best chance, they need to be prepared for the change. I recommend moving them outside on an overcast day, just to be safe.

What happens next?

Make sure to bookmark this post and follow along for most useful tips from an experienced backyard gardener. But once the plants are in the ground, it doesn’t stop there! Head over to the composting category to learn more about how to nourish your seedlings, whether they’re growing in raised garden beds or containers.

Add this post to your reading list: Beginner’s Guide to Starting Seeds Indoors

And make sure to opt-in to the newsletter list for my weekly email tips and the arrival of my upcoming seed starting workshop. You can find that on the sidebar, or on the contact page.

About Marion

Learn the gentle art of nurturing your garden using simple organic methods like composting that have been field-tested for nearly 40 years by Marion Owen, New York Times bestselling author.