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All Things Garden,  Beginner Basics

Transplanting Seedlings Outside: Tips for Success

Ah, that special moment when the seedling babies you’ve gingerly raised indoors are finally ready to move out into the big bad world of the garden. Or, is it more like those lanky teenagers have long overstayed their welcome – and you’re ready to kick them out of the house? Either way, nothing is more rewarding than transplanting seedlings outside… except harvest time of course! 

Read along to learn when and how to transplant seedlings outside into your garden. We’ll cover how to properly prepare seedlings to be transplanted, steps for planting day, and follow-up care. The process is generally quite straightforward and simple, yet I have several tips to share to help prevent transplant shock – and grow the most healthy and productive plants possible! These tips can be applied to any type of vegetable, herb or flower seedlings that you started from seed, or those you purchased at your local nursery.


At a Glance


This article will cover:

  • How to harden off seedlings
  • The best time to transplant
  • Tips to amend soil
  • Best spacing and planting practices
  • Benefits of worm castings and mycorrhizae
  • Water and mulching tips
  • More ways to prevent transplant shock
  • How to protect seedlings from pests or harsh weather



BEFORE TRANSPLANTING SEEDLINGS OUTSIDE


Harden off seedlings


A very important step prior to transplanting seedlings outside is to ensure they’ve gone through a process called “hardening off”. Hardening off is when indoor-raised seedlings are gradually exposed to a wider variety of elements than they’ve otherwise received while protected indoors, such as direct sunlight, cooler temperatures, and wind. The process prepares them for the transition to the great outdoors, and greatly reduces the risk of transplant shock or injury during inclimate weather. (Heads up: store-bought seedlings have already been hardened off for you!)

Start hardening off your seedlings about a week prior to transplanting outside. Begin by bringing the seedlings outdoors (on a calm and mild day) for just a few hours at a time and in a mostly shady location at first. Then over the course of the week, gradually increase the time and direct sunlight they receive. By the end of the week, they should be sufficiently hardened off! However, we start strengthening our seedlings far earlier than a week before transplant day. For instance, the movement created by an oscillating fan nearby (used indoors just a couple weeks after sprouting) helps their stems become nice and strong. We also turn their heat mats down and then off a couple weeks earlier. 

Related: Learn more step-by-step details about hardening off here, and all our of top indoor seed-starting tips here.


DeannaCat is holding a bok choy seedling by the rootball. Beyond lies a raised garden bed with two rows of newly planted seedlings, two 6 cell packs of seedlings remain sitting atop the soil. Some transplant holes sit empty as they await for new seedlings. Proper spacing is very important when it comes to transplanting seedlings.
Bok choy, collard green, and kale seedlings – all hardened off and ready to be transplanted outside.


When to transplant seedlings outside? Know your zone


Before transplanting seedlings outdoors, it is important to familiarize yourself with your area’s frost dates and ideal planting times. Young seedlings are particularly susceptible to frost damage or even death (including plants that will grow up to be quite cold-hardy once they mature). Even if there is little-to-no risk of frost, transplanting seedlings too early can make them unhappy and more prone to stalling, stunting, or disease. For example, our area is virtually frost-free… but that doesn’t mean we should plant tomatoes outside in February! 

Therefore, plan to transplant seedlings outside at a time that is appropriate both for the plants and your zone. I realize that sounds a bit ambiguous, so check out our Homestead and Chill planting calendars for an easy visual guide! We’ve prepared calendars that illustrate the ideal time to start seeds indoors or out, and when to transplant seedlings outside – for dozens of vegetables and every USDA hardiness zone.


A planting calendar for Zone 8, it has many different vegetables lined up on the left side of the chart and all of the months of the year listed on the top of the chart. Each vegetable has different colored lines that correspond with when to start seeds inside, transplant outdoors, and plant seeds outside, along with corresponding last frost date and first frost date where applicable. The lines start left to right, showing what months you should do each particular task depending on the season and where you live.
The green lines represent a range of ideal transplanting times!


Check the weather forecast


When the target transplant day comes, check your local weather forecast. Avoid transplanting seedlings outside if there is any stormy or extreme weather predicted in the coming days ahead. Check at least 5 to 7 days out for frost, heat waves, high wind, heavy rain, hail, or similar. Even if you’ve already hardened off your seedlings and are otherwise ready to go, it’s best to wait until more favorable conditions are on the horizon. If possible, choose a nice calm, temperate day to transplant seedlings outside. 


Amend or fertilize your soil


Finally, prepare your garden soil before you transplant seedlings outside. Plants need ample and diverse nutrients to successfully grow and produce. As they grow, they use up existing nutrients within the soil, which can leave it relatively depleted at the end of each growing season. So, it is important to replenish nutrients by amending your garden bed soil between crops or seasons. 

In our no-till style garden, we prefer to use natural, mild, slow-release fertilizers like alfalfa meal, kelp meal, and neem meal – OR something all-in-one, like this organic all-purpose fertilizer. All of these dry fertilizers are sprinkled over the soil, lightly scratched into the surface, and watered in. Additionally, we amend the soil with plenty of aged compost! Learn more about our soil amendment routine in this article. 

In preparation for transplant day, it’s best to fertilize soil a week or so in advance (if using dry, meal-type fertilizers). Water it in a couple times to allow the fertilizer to become incorporated into the soil. This helps everything mellow out and prevents ‘burning’ the seedlings. However, we often add fertilizer to our garden soil the same day we transplant seedlings outside! With busy schedules, we can’t always follow best practices. However, we go lighter than the package recommendations to ensure nutrient burn won’t be an issue.  

After that, it’s go time!


An empty raised garden bed lies in the foreground with dry amendments covering the top most portion of soil. There are two remaining beds that lie empty that have yet to be sprinkled with amendments. The amendments will be scratched into the surface of the soil before being thoroughly watered before transplanting seedlings into the raised beds.
After sprinkling over the slow-release organic fertilizers, we lightly scratch it into the surface (top couple of inches) of the soil. We do not till and mix it deeply.


HOW TO TRANSPLANT SEEDLINGS


How far should I space my seedlings?


Follow the general spacing recommendations for the particular types of plants and varieties you are growing. When plants are overcrowded, they will compete for root space, nutrients, sunlight, and airflow. Crowded plants are also more prone to disease. I’ll admit that I sometimes push the suggested limits a tad, but do my best to give everyone the space they deserve and need. You can also fudge the spacing recommendations a bit by planting seedlings in offset rows, as opposed to a perfectly straight line. Also remember that even if a garden bed full of baby seedlings looks sparse, it WILL fill in.


General plant spacing recommendations:

  • Space large bushy plants like tomatoes, summer squash, Brussels sprouts, cauliflower, broccoli and cabbage at least 18 to 24 inches apart.
  • Smaller plants such as peppers, eggplant, bush beans, kale and other leafy greens can be planted slightly closer together – around 12 to 18 inches, depending on variety.
  • Root crops like radishes, carrots, turnips, or garlic grow only inches apart – yet those are all best to direct-sow and thin in place, rather than transplant. 
  • If you haven’t already, thin each seedling down to only one plant per space.


Related: Visit the in-depth grow guides for tomatoes, cauliflower, summer squash, carrots, radishes, kale, green beans, or garlic by clicking on their name here.


A raised garden bed with three rows of newly planted seedlings taking up 1/3rd of the beds space. Some transplant holes sit empty as they await new seedlings. Proper spacing is very important when it comes to transplanting seedlings.
A birds eye view of two rows newly planted bok choy seedlings. A soaker hose is visible amongst the top soil as it winds around the seedlings in a snake pattern.
An example of offsetting rows. I planted 4 bok choy seedlings along the very front of this bed, and then 5 in the row behind it, offset diagonally between the first. Then next (3rd) row went back to four seedlings, lined up with the first row.


Where to plant what


The majority of common vegetables, flowers and herbs prefer full sun – or as much as you can give them! This is especially true for heat-loving summer crops like peppers, tomatoes, corn, squash, beans, cucumbers, and more. Most cool-season crops like leafy greens, radishes, cauliflower, fava beans, green onions, or peas can tolerate partial shade, but may also grow less prolifically.

Also be mindful of the height plants may reach as they mature in relation to your gardens sun exposure. Avoid planting tall crops like tomatoes in a spot that would eventually shade out the shorter plants around them. Here in the northern hemisphere, we keep our tallest plants and trellises along the east and northern sides of our garden beds to maximize the southern sun exposure the rest of the bed receives.

Finally, if you’re wondering “what plants should I plant together?” – that’s a great question, and a subject all of it’s own! Intermixing various plants creates a beautiful aesthetic, and may also provide added benefits like natural pest control. On the other hand, some types of plants don’t particularly care for one another – like peppers and beans. Please visit our Companion Planting 101 article to learn more. It includes a free printable companion planting chart too!


Raised garden beds overflowing with plants such as squash, calendula, borage, marigold, carrots, beans and tomatoes. The varied and bright colors of the flowers pop against the vibrant greens of the plants. Paver lined gravel pathways separate the raised beds. Beyond lies flowering perennials and a wall of trellised passion vines.
Party in the back, party in the front. Note the taller plants and trellises are along the northern side, leaving the shorties plenty of southern exposure for maximum sunlight.


Create Planting Holes


Dig a hole about the same size as the seedling root ball (or just larger). If the seedlings have become leggy (tall and stretched out) and you want to bury a portion of the stem, make the planting hole a tad deeper. Tomatoes, tomatillos, peppers, kale, and other brassicas like cabbage, collard greens, or broccoli do not mind their stems being buried a little. That is, as long as the seedlings aren’t super young and tender, and they have been properly hardened off! Otherwise, tiny tender stems have an increased risk of rotting below the soil line. Read more about preventing, fixing, and planting leggy seedlings here. 


Optional: worm castings and/or mycorrhizae


Now, you could plant the seedling as-is. However, we like to spoil our transplants and give them a little extra boost of nutrition and love! First, we mix a small handful of worm castings to the bottom of every planting hole. Worm castings, also known as ‘black gold’, are a wonderful microbially-active fertilizer; gentle but potent. The organic matter in worm castings also improves soil structure to increase moisture retention and aeration. We use worm castings from our compost worm bin, but you can also buy them.  

In addition, I also highly recommend inoculating the planting hole with mycorrhizae.  Mycorrhizae are beneficial fungi that help increase nutrient uptake, root growth, fruit production, and disease-resistance! It can also prevent transplant shock. Mycorrhizae is most beneficial for plants that produce flowers and fruit (tomatoes, peppers, cannabis, squash, eggplant, fruit trees, etc) and it doesn’t make strong associations with the roots of brassicas like cabbage or kale.

Because mycorrhizae need to bind to the plant root system to survive, sprinkle granular mycorrhizae either directly on the root ball itself, or along the inner walls of the planting hole that will soon come in contact with the roots. A little goes a long way! (Follow the instructions on your package.) Don’t have any on hand come transplant day? You can also use a water-soluble mycorrhizae to water the seedlings after planting!

Related: Vermicomposting 101: How to Make and Maintain a Simple Worm Compost Bin


DeannaCat is holding a small amount of worm castings in her hand that will be added into the planting holes. The background shows two seedlings laying on their sides next to two transplanting holes. When transplanting seedlings it is a good idea to add a boost of microbes by using vermicompost.
A small handful (about 1/4 cup) of worm castings getting mixed in to each planting hole for these kale seedlings.
A 1/2 teaspoon measurement is shown full of mycorrhizae granules. The backdrop is garden soil with a transplant hole, a tomato seedling with exposed rootball is lying on its side next to the hole, a trowel and garden glove lay below that.
Granular mycorrhizae. Sprinkle it in the planting hole or right on the root ball, but make sure it comes in contact with the roots.
The rootball of a tomato seedling is shown after it has been lightly dusted with mycorrhizae. The white roots of the plant are crossing this way and that, the soil of the garden bed is the backdrop.
Dusting a tomato seedling root ball with mycorrhizae. Lightly pat it on to make it stick!


Plant the seedlings


Gently remove the seedling from its container, but avoid pulling on the stem itself. Instead, carefully tip the seedling container on its side and lightly push up from the bottom and/or squeeze the sides of the container to ease the root ball out. Avoid ruffling the roots unless they’re clearly root bound and winding around each other. In that case, gently loosen the roots before planting the seedling.

Place the seedling in the planting hole. Adjust the depth as needed so that the existing root ball will be level or just below the soil surface.

For extra leggy seedlings, it’s okay to bury them up to their first set of branches or leaves, but usually no more than a couple inches deep. An exception is tomatoes. Tomato seedlings (and tomatillos) are known for their tendency to grow fresh roots off of buried stems, so go ahead and plant those suckers up to 6 inches deep if needed. Remove lower side branches that would end up below the soil first. I’ve heard conflicting things about whether or not squash, eggplant, and cucumber seedlings like their stems buried, so play it safe and bury them minimally or not at all. 

Once the seedling root ball is settled in it’s planting hole, gently pack soil around it to fill the hole. Be sure to get around the sides, not leaving any voids. However, don’t press down too firmly and compact the soil! Looser soil is better at absorbing water, and also draining away excess standing water.

Related: Growing Organic Tomatoes: How to Plant, Feed, Prune, & Grow Tomato Plants


A tomato seedling is sitting in its transplant hole, it is going to be buried slightly deeper than its root ball so the lower leaves are being removed as the portion of stem will soon be covered in soil. When transplanting seedlings like tomatoes, bury leggy seedlings deep and they will grow roots off their stems.
This tomato seedling isn’t very leggy, but I will still bury its main stem a few inches deep. First, I pinch off and remove the lower branches and leaves that would otherwise end up below the soil.
DeannaCat is holding the top portion of a leggy bok choy seedling as it sits in its transplant hole. The stem of the seedling has gotten a little long so the seedling will be buried slightly deeper so the base of the plant is resting just above the soil line.
This bok choy transplant is just a tiny bit leggy. I will bury the stem so that the base of the plant will be resting level on top of the soil. (See photo below)
A leggy bok choy seedling has been transplanted into a garden bed. The base of the plant is sitting just above the soil line, multiple 6-cell packs of seedlings sit in the background atop the soil of the garden bed. When transplanting seedlings that are leggy, it is sometimes a good idea to bury them a little deeper.


AFTER TRANSPLANTING SEEDLINGS OUTSIDE


Water


Once your seedlings are tucked away in their new bed, give them a good water! In the coming weeks, maintain the soil consistently damp (but not soggy). Keep in mind that young seedlings have very small, concentrated root systems – so be sure to water immediately around the base of the plant. Yet don’t neglect the rest of the bed! Watering the soil between small plants (and also watering deeply) will encourage their roots to spread. The more expansive the root system, the more access to nutrients and water the plants have, and the more robust and healthy they will become. 

Related: Garden Irrigation Solutions: DIY, Efficient, and Non-Toxic Watering Options


Aaron is watering young bok choy and kale seedlings with a watering can. There are six rows of vegetables and the front two are the only rows that have been watered thus far. The soil surrounding each plant is getting watered to allow their roots to spread. Hoops are visible over the bed although the row cover has been removed for watering purposes.


Mulch


After transplanting seedlings outside, add mulch around them. Mulch is incredibly beneficial, but often overlooked! It reduces evaporation and runoff to keep soil evenly moist, and also buffers soil and plant roots from temperature swings.

Mulch in the spaces between the seedlings, but not directly against the stems. If it’s pressed right against young stems, mulch may increase the risk of rotting or pest issues. Therefore, maintain a few inches of open soil around the base of each plant. We personally love to use compost mixed with a woody ‘soil-building conditioner’ (similar to a very fine bark). Those items double as a slow-release fertilizer and add organic matter to the soil as well! 

Related: Pros and Cons of 8 Popular Types of Mulch including compost, bark, straw, leaves, and more. 


Protection


After you kick them out of the house, your babies may still need a helping hand. After transplanting seedlings outside, keep an eye on the weather forecast and be prepared to offer them protection if needed. Remember, young seedlings will NOT be happy when exposed to a hard frost. Also, consider their vulnerability to wandering pests such as rabbits, squirrels, or deer. You may not find the need to cover or protect your seedlings; it depends on the conditions in your garden.

We heavily rely on our hoops and insect netting to protect young seedlings from the ravenous beaks of wild birds in our garden – which also blocks pest insects like cabbage moths. We keep leafy greens covered for at least a month or two. The birds don’t seem to bother tomato, pepper, and squash seedlings as much. Hoops can also be used to support various row covers like frost blankets or shade cloth if significant temperature swings roll in. Other frost-protection tools include cold frames, individual cloches, or even bed sheets! 

Related: Using Hoops and Row Covers for Pest Control, Shade, and Frost Protection and 7 Ways to Protect Plants from Frost Damage


A two part image collage, the first image shows a raised garden bed with young bok choy and kale plants. The garden bed is covered using hoops and row covers to protect them from pests. The second image shows the garden bed with a portion of the row cover pulled up and over itself to reveal the plants within. When transplanting seedlings, one may need to protect them from pest before they are large enough to withstand damage.
Keeping our young seedlings protected from birds, who can’t resist leafy greens! We have the shorter version of Gardener’s super hoops on our garden beds, ideal for creating low tunnels in beds 2 to 4 feet wide. Here, we added optional base extenders for these 4.5 foot wide beds for added height. They also have a hi-rise hoop option for wider beds or taller plants, which are twice the length/height).


More ways to reduce transplant shock (and boost growth)


There are a number of very gentle but effective liquid solutions you can ‘feed’ your seedlings with to reduce transplant shock and encourage rapid new root development, including:

  • Aloe vera soil drench: We often do this for freshly transplanted seedlings along with new trees or edible shrubs. Essentially, it involves blending up some fresh juicy aloe vera leaves with water, diluting it significantly, and then watering each plant with about a cup of the final solution. Like it does for human skin, aloe vera has potent nourishing and regenerative properties for plants too! Learn how to make homemade aloe vera fertilizer here.

  • Seaweed extract: Dilute seaweed extract is another excellent option to provide young seedlings a boost – especially if you don’t have access to fresh aloe vera leaves! We love and use this seaweed extract. Mix it with water per the instructions on the bottle, and feel free to learn more about its benefits in this article. 

  • Compost Tea: This option is my favorite from this list – and something you can do after transplanting seedlings outside, or any time throughout the growing season! We feed our garden actively aerated compost tea (AACT) several times per year. It’s kind of like our ‘secret sauce’. AACT tea is made by brewing compost in water with the addition of an air source (e.g. an air pump and bubbler) and a small amount of sugar (e.g. molasses). The process dramatically increases the number of beneficial bacteria in the brew, and results in highly bioavailable nutrients for your plants. Did you know that plants cannot take up nutrients without the assistance of bacteria and fungi? Check out our tutorial on how to make AACT here – video included!


A two part image collage, the first image shows DeannaCat holding a glass beaker full of fresh aloe vera tea.  A garden bed with small vegetable plants are in the background. The second image shows a watering can being used to water a tomato plant with dilute seaweed extract. These are two great ways to help out your plants when your transplanting seedlings.
Fresh aloe vera soil drench on the left, seaweed extract on the right. Sometimes we use both mixed together!
DeannaCat is holding a Pyrex liquid measuring cup with compost tea filled to the brim, well above the one cup measurement. Beyond it the base of a tomato plant with a cluster of green fruit.
Feeding tomatoes with homemade actively aerated compost tea. You can use AACT just about any time, and as frequently as once a month.


Now you know all our secrets to success!


Are you ready to get planting? I hope all of these tips for transplanting seedlings outside will help you grow the most healthy, happy plants possible. Remember, you don’t have to do alllll of these things either! If I had to pick just a few key steps, I’d focus on using a mild organic fertilizer before planting, mycorrhizae on transplant day, and mulching thereafter. But don’t skip the hardening off process!

Please let us know if you have any questions in the comments below. If you found this information valuable, please spread the garden love by pinning or sharing this post. Until next time, happy planting!



DeannaCat signature, keep on growing

10 Comments

  • Leslie

    Hi there! Thank you for sharing your wisdom – you are one of my go to resources! Started a bunch of flower starts inside and have potted them up and moved them outside in a small covered greenhouse. I included a bit of compost when I potted them up and also have fed with kelp. They just aren’t looking super green and lush anymore! Is it time to just put them in the ground and hope for the best? Any other insight as to why they are yellowish? We’re in zone 8 up here in Seattle.

    • Aaron (Mr. DeannaCat)

      Hello Leslie, what size pots do you have them in? If they were slightly root bound before you potted them up they may still be slightly unhappy. Also being in Seattle, the weather may still be a little cool for them outdoors where they will really start to take off once the weather warms some. It is sometimes best to just let the seedlings or plants do their thing as they will usually shape up in time. Good luck and happy gardening!

  • Kristen

    Such a helpful article! I may have missed this tip in the article, but at what size to you recommend transplanting the seedling?

    • Aaron (Mr. DeannaCat)

      Hello Kristen, it really depends on the type of plant that you will be transplanting out and assuming that they have been hardened off properly with fair weather in the forecast. If the weather is going to be cold and rainy, transplanting seedlings out isn’t a great idea because they could become stunted and won’t grow much during this time. At the very least, once you start to see a plants roots emerging from the bottom of the pot or soil, it is likely forming a root ball that has taken up the space that has been offered and can be potted up into a larger size or transplanted out into the garden. We want the plant to be mature enough to withstand pressure from pests or wind and weather. Hope that clarifies that a bit more for you and good luck!

    • DeannaCat

      Hi Jim! Thanks so much for the feedback! I’m glad you’ve ventured into the seed starting world. It’s so fun and rewarding. Enjoy!

      • Sara

        Hi! Love your articles guys!! I have a question- What’s the best way to use netting set-up to protect transplanted seedlings where you have a vertical trellis? I have cucumbers and peas that the grasshoppers are starting to eat here in Florida (zone 9B) and don’t know the best way to wrap them up. Thanks so much for any advice.

        🌱Sara

        • Aaron (Mr. DeannaCat)

          Hello Sara, thank you so much for reading! This is an issue that we have often thought about ourselves although it is difficult to protect the plants without fully covering the entire trellis. I would most likely try and make a sort of triangle with the bottom of the netting spaced a foot or so away from your plants while bringing the netting over the top of the trellis and back down to the ground. You can use clothespins or heavy duty clamps to secure the netting to landscape staples which would be placed into the ground, add additional clamps to the sides to try and close up the openings as best as possible. It may not be the best thing to look at or fully covered as the sides may still be open to the outside but I would imagine it would greatly reduce the amount of pest damage as they have less space to access your plants. Usually once your plants become large enough they won’t be impacted as much by the pests as they are when they are smaller. Hope that helps and good luck!

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