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All Things Garden,  Beginner Basics,  Indoor Gardening

How to Prevent and Fix Leggy Seedlings

Are you new to growing vegetables, herbs or flowers from seed? Have you ever wondered what’s up with the term “leggy seedlings”? Or, do you have some freshly-sprouted seedlings that are looking extra lean and tall? (Spoiler alert: they might be leggy!) If you answered “yes” to any of these questions, then you’ve come to the right place. This article will teach you everything you need to know about leggy seedlings: what they are, why they’re a bit of a problem, how to prevent them, and even how to correct leggy seedlings once they grow! 

Be sure to also stop by our Seed Starting 101 article for more tips on raising the most robust seedlings possible.



What are leggy seedlings? 


Seedlings are described as “leggy” when they grow very tall, skinny, and lanky. In the seedling world, taller does not equate to better, healthier plants! On the contrary, thin leggy seedlings are typically quite weak and fragile. They may also be pale or yellow-looking.

There is no exact height that seedlings must surpass to officially classify as leggy. It’s more about comparing them to healthy seedlings of the same variety that are grown in ideal conditions, which will stay much shorter compared to their less-happy, leggy counterparts. With time and experience, you’ll get a feel for what is considered grossly leggy or not.


Two 6 cell seedling packs are sitting next to one another on a wooden greenhouse bench. The black seedling pack on the left has many leggy seedlings growing out of each cell, they are flopping over the edges and can't support their weight. The brick red color cell pack on the right contains healthy seedlings, each cell has multiple sprouts emanating from it, they are standing straight up and are more squat in nature than their counterparts to the left.
On the left: Leggy bok choy seedlings, about three inches tall. On the right: Healthy, short and stocky bok choy seedlings, about half the height of the leggy ones.
A close up of two different seedling cell packs, one contains seedlings that are flopping over the edges, the stems unable to support the weight of the rest of the plant. The other pack contains seedlings that are much shorter and more squat, they are standing straight up and their stems look thicker than their leggy counterparts.
The leggy seedlings (left) only received the natural light in our partially-shaded greenhouse (during winter), while the healthier ones on the right were under grow lights for over 14 hours per day (started just a few days later).


What causes leggy seedlings?


The primary cause of leggy seedlings is lack of sufficient light, either in brightness or proximity to the plants. This can happen when gardeners start seeds indoors, or when seeds are planted outside in a too-shady location. Even in our greenhouse (which is partially shaded in the afternoon) we need to use grow lights in order to keep our seedlings happy. Paired with being stretched out tall, leggy seedlings will also often lean to one side – towards the direction of the brightest source of light around. They are desperately reaching for the sun! 


Are leggy seedlings bad?


In general, a leggy growth pattern on seedlings is not ideal. Rather than focusing their energy on developing thick, strong, sturdy stems, leggy seedlings become increasingly thin, fragile, and weak the taller they become. Their top-heavy nature makes them more vulnerable to flopping over, breaking, or other damage. Especially in the face of wind or other elements. Leggy seedlings are also more prone to ‘damping off’ – a condition when seedlings suddenly wilt, become very thin or rot right above the soil line.

Come planting time, not all types of seedlings like to be buried extra deep to compensate for their leggy stems. That practice also comes with the risk of rotting stems. However, many leggy seedlings can be saved (see “how to fix leggy seedlings” below). Tomato and tomatillo seedlings are particularly forgiving. Packed in a tight bunch and harvested young, it also doesn’t really matter if homegrown microgreens become leggy.

All in all, it is best practice to try to prevent leggy seedlings in the first place. Follow the tips below!


A birds eye view of two cell packs full of young brassica plants. They are tall and lanky, flopping over the edges of the containers.
Dang boo, you’ve got legs for days!


How to Prevent Leggy Seedlings


  • Provide ample bright light to seedlings immediately after germination. All it takes is a day or two in the dark for a young sprout to get irreversibly leggy!

  • When starting seeds indoors, plan to provide seedlings with supplemental light (aka a “grow light”). Unfortunately, a sunny window generally doesn’t provide enough light on its own. 

  • As soon as your seeds sprout, turn the grow lights on. If you’re worried about missing this crucial moment, turn on your grow lights a few days after sowing seeds (but before they’ve sprouted). The vast majority of seeds do not need light to germinate, but that way the light will be on and waiting for the moment they do! 

  • Remove any cover used over your seed starting tray to aid in germination (e.g. humidity dome or other) soon after the seedlings sprout, especially if it is not transparent.

  • Keep grow lights suspended low over the seedlings. Even with a very bright grow light, seedlings may get leggy if it’s hung too high. Most fluorescent lights can stay as close as a few inches above seedlings, while LEDs usually need to be kept higher to avoid burning the plants. Follow the light manufacturer’s recommendations. Raise the lights as needed as your plants grow taller.

  • Provide a minimum of 12 hours of bright light (14 to 16 hours is ideal) and 8 hours of darkness. I highly recommend using a simple light timer! Set it and forget it. 

  • When starting seeds outdoors, direct sow seeds in a suitably sunny location and at the right time of year for the type of plant and your zone. Starting seeds outdoors during winter (when daylight hours are usually shorter) can lead to unhappy seedlings, especially in a garden space that receives partial or full shade.


Learn more about choosing and using grow lights in this article, which covers the key differences between LED and fluorescent lights, ratings, best practices, and popular grow light options.


A close up image of many 6 cell pack seedling trays with tender seedlings sprouting upwards. T5 fluorescent lights are hung just inches above the top of the seedlings.
Keep grow lights hung low over the seedlings! (Read instructions on LED lights. Some may burn seedlings if too close)


How to Correct or Fix Leggy Seedlings


Once you have leggy seedlings, there isn’t anything you can do to make them short again. However, if you act quickly, you may be able to prevent them from becoming even more lanky. Furthermore, there are a few tricks to help them gain strength and still live out their best life possible.  


1) Provide more light as soon as possible


The best way to fix leggy seedlings is give them more light, ASAP! This could mean adding a supplemental grow light if you’re not using one already, upgrading to a stronger light, or lowering your current light closer to the seedlings so it is more effective. As you lower a light, there is a smaller area of well-lit space available below it’s canopy. Thus, it may require several lights or one larger unit to provide adequate light over a large number of seedling trays. Otherwise, the stragglers around the perimeter are left out! In that case, take turns rotating different trays directly under the light every day until you can provide more. 


2) Turn heat mats off (or down)


If you are using a seedling heat mat to start seeds indoors and your seedlings appear to be getting leggy, go ahead and turn the heat mat off or down. Warmth helps to expedite seed germination (a great thing!) but can also encourage seedlings to grow faster. When seedlings are already lookin’ on the leggy side, let’s not do anything to encourage them to get even taller, shall we? This recommendation comes in addition to adding more light of course. 

We personally love to use these seedling heat mats that have a built-in thermostat control and temperature probe. After germination, we set our heat mats to come on only when the soil temperature drops below 65-70°F. This keeps our heat-loving summer crop seedlings (tomatoes, peppers, basil, flowers, etc) happy in our greenhouse during the winter to early spring, where it can get quite chilly overnight but also very warm during the day. You can easily apply the same set-up indoors, in a garage, or anywhere you’re raising seedlings.


DeannaCat is holding a thermostat and temperature probe from a seedling heat mat. Beyond lies trays of seedlings and trays of soon to be sprouted seedlings that are covered with humidity domes until they germinate. Two T5 lights are hanging above.
A seedling heat mat with thermostat control. The little metal probe goes inside the soil (pressed down towards the bottom/warmest spot) and controls when the heat mat turns on or off, depending on the desired temperature set. We have a couple 4 foot mats, though they’re also available in smaller sizes.


3) Start over


Okay, hear me out here. I’m not talking about starting a new round of seeds when you’re several weeks or even months deep into the seed-starting season for your zone. However, if you have ample seeds and things are looking leggy only a few days after germination, it might be in everyone’s best interest to start fresh rather than fussing over leggy seedlings for the rest of the season. 

For example, just the other day I started a few 6-packs of bok choy seeds on a heat mat in a dark spare room. I had every wonderful intention of checking them frequently and moving them out to the greenhouse (and under a grow light) as soon as they sprouted. Welp, I forgot to check on them for over 24 hours, they sprouted, and already looked way too tall for my liking. So I simply started more bok choy seeds, and kept the leggy seedlings as the ‘bad example’ for this post! 


Two packs of new emerged leggy seedlings that are tall, skinny, and pale. Their first leaves are more yellow as opposed to green.
These are the forgotten bok choy seedlings from the story above. I only “forgot” them in a dark room for ONE day after spouting, and they immediately grew leggy and pale. Their color will improve once they’re in better light, but I knew I wanted to start over with new seeds. (I allowed these to grow so I could take photos – these are the leggy ones shown earlier in the article).


4) Make them stronger


If you have leggy seedlings, you very well might be able to plant them anyways! But first, they need to be significantly strengthened in preparation. Early on, they’ll be too weak to plant outside. Also, young leggy seedlings are usually too tender to bury deeper in soil without the stems potentially rotting.

Be sure to thin your seedlings down to just one sprout per cell or container within a couple weeks after sprouting. Thinning reduces competition for nutrients, space, light, water, and improves air circulation. I always suggest trimming out unwanted sprouts rather than plucking and pulling. After that, there are three main ways to turn your leggy seedlings from puny to mighty:


Add movement 

To strengthen seedlings, introduce a light wind with an oscillating fan. Don’t put it on full blast, but enough to create gentle shaking and movement. Movement helps the stems of leggy seedlings become more tough and strong. Tickling seedlings with your hands can help in the same manner. Yet a fan is beneficial in more ways than one! Ample airflow also prevents fungal disease and damping off. I recommend using a fan on indoor seedlings whether they’re leggy or not. 


Use mild fertilizer and “water from below”

Another way to boost the health of leggy seedlings is to feed them! Once seedlings develop their first set or two of true leaves (the ones that grow after the initial two leaves that are often heart-shaped) you can begin to feed them with a very mild liquid fertilizer. The seedlings should be at least a few weeks old by this point, since they do not need or care for fertilizer much younger than that.

We prefer to feed our seedlings with seaweed extract, though fish emulsion is another popular choice. Be sure to dilute whatever you use per the instructions on the bottle. Then, add the liquid fertilizer/water into the lower tray that the seedling containers are sitting in. The soil will soak up what it needs from the bottom. That is the way we always suggest to water all seedlings anyways, but especially the leggy ones! Pouring water in from the top runs the risk of knocking them over, and doesn’t provide even moisture. When you water from below, it encourages their roots to grow deep – making the plants more strong.


DeannaCat holding a one gallon watering can, pouring water from the spout into the bottom of black trays full of seedling containers. The setting is in a greenhouse with pea gravel floor, and dozens of small green plants are growing in the small pots within the seedling trays.
Watering from below: add an inch or two of liquid into the lower tray, but only enough that the seedling containers/soil will soak up within a few hours. Do not let them sit in standing water constantly. If there is still water in the tray 4 to 5 hours after watering, carefully pour it out.


Harden off

Finally, be sure to always harden off leggy seedlings before transplanting them outside. ‘Hardening off’ is the process of slowly introducing seedlings that were raised indoors to the outdoor elements. This generally involves taking the seedlings outside each day over the course of a week, starting with just a few hours in the shade and gradually increasing the time and amount of direct sunlight. Like a fan, this makes the seedlings stronger and more prepared to face challenges such as wind, rain, hot sun, or cold conditions. See step-by-step hardening off instructions here.



Potting Up or Planting Leggy Seedlings 


Can you bury leggy seedlings deeper in the soil? 


Generally, yes, you can plant leggy seedlings deeper in the soil to help compensate for the extra-long stems! However, avoid the temptation to plant them deeper right away, when they’re still very young and tender. Weak, thin, small stems may rot once they’re buried in damp soil. Wait at least several weeks, and after taking steps to strengthen and/or harden off the leggy seedlings as described above.

Once the stems are more tough and strong, you should be able to bury a portion of the leggy seedling stem – either by potting them up, or transplanting them outside. Or, you may do both! For instance, we start our tomatoes in small 4” seedling pots. Then after about a month, we pot up the seedlings into larger 8” nursery pots and bury the stem by a couple inches at that time. Then when we transplant them out into the garden, we can bury the stem a few more inches if needed.  

See related: Potting Up Seedlings: When, Why & How


DeannaCat is touching the root ball of a tomato seedling that is sitting inside of a larger 8 inch nursery pot. The root ball is a couple inches below the top of the pot, the stem will be buried up to that point with soil during the potting up process.
Potting up a leggy tomato seedling from a 4″ nursery pot to an 8″ pot. I put a small amount of soil on the bottom of the new pot, but will otherwise keep the root ball deep in the new container so that I can bury the stem a couple of inches. It looks like I also removed a lower branch or two.


How deep can you plant leggy seedlings? 


Well, that depends on the type of plant and size of the seedling! The goal is to bury the leggy seedling stem enough so that the plant isn’t too top heavy and can successfully grow. Otherwise, I personally err on the side of caution and avoid burying them more than necessary. 


  • Most common garden vegetables don’t mind if you bury their stem part way or all the way up to their first set of true leaves (or first set of lateral branches). You can do this with peppers and members of the brassica family: kale, collard greens, broccoli, Brussels sprouts, or cauliflower.

  • If the vegetable is one that should normally form a head or bulb right at the soil line, then you’ll want to bury it up to that point – where the stem branches and begins to form the main crop, so that its weight will be supported on the soil surface. Consider a head of lettuce, bok choy, cabbage, or kohlrabi for example. 

  • You can plant some seedlings even deeper. Tomatoes and tomatillos are prime examples. Due to their advantageous root systems, it is a common practice to remove the lowest few branches and bury leggy tomato seedlings up past that point (planting up to half of the plant underground). Tomatoes and tomatillos will grow new roots off of the buried portion of the stem! More roots equals a more robust and healthy plant.

  • It is less necessary to deeply bury seedlings of plants that will continue to grow tall branching stems well above the soil line anyways, such as flowers or herbs.

  • I’ve heard conflicting things about how well eggplant, squash, and cucumber seedlings take to being planted deeply (as they may be more prone to rotting). Therefore, play it safe and only minimally bury those if needed, and do so in well-draining soil that won’t hold copious moisture around their stems.


A cauliflower seedling sitting in its newly formed planting space in a raised garden bad. Its root ball is sitting an inch or two below the soil surface. Beyond lies a few other cauliflower in the same row as well as a couple rows of red onions.
Planting a slightly leggy cauliflower seedling, burying the stem a couple inches (up to the first set of leaves).
DeannaCat is holding a young tomatillo plant that has been pulled out of a garden bed due to the plants structure which wasn't ideal. The rootball and second ball of roots is what is illustrated most. It shows the original root ball that was formed as a seedling, however, above that for about 4 to 6 inches there are many more roots growing from the main stem after the tomatillo seedling was planted deep to counteract it being leggy. Beyond lies another garden bed with kale, zinnia, sunflower, and calendula. A chicken is standing in between the two beds looking at the suspended root ball and plant.
This was a tomatillo seedling that got WAY too tall in our greenhouse. It had ample light, but we started it too soon (I forgot how quickly tomatillos get large!) so I buried the stem a good 6 inches deep when transplanting it into the garden. I still ended up starting a new seedling to replace it because I didn’t like it’s growth structure, so I dug it up about a month later to replace it. All of these new roots grew off the buried portion of the stem in that short time! Tomatoes do something similar, but not quite as vigorously.


And that concludes this lesson on leggy seedlings.


All in all, do not feel bad if your seedlings are a little leggy! Even the most experienced gardeners doing all the “right” things grow some slightly leggy seedlings sometimes – ourselves included. As you saw in this article, all hope is not lost! There are a number of ways to prevent and fix leggy seedlings. Plus, you’ll learn from your mistakes and improve next season. That is one thing I love about gardening: there is always something new to learn, and there is always next year.

Please let me know if you have any questions in the comments below. Also, please pin or share this article if you found it valuable! Cheers to growing happy seedlings!


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9 Comments

  • Suzanne Phend

    What can I do, if anything, if I have some burnt tomato leaves? I lowered my lights because my seedlings became leggy overnight! I have the lights on a timer for 16 hours a day and one day they were great, the next they were so leggy! I must have had the lights too high. So, I lowered the lights a bit and we went out of town for two nights. I came back and a lot of my tomatoes have burnt leaves. Do I need to scrap them and start over or just cut off the burnt leaves? Thanks so much!!

    • Aaron (Mr. DeannaCat)

      Hello Suzanne, unfortunately that happens sometimes, they can grow so fast and in a days time they are growing into the lights! Your seedlings should rebound just fine, it really depends on how large they are and how much leaf you want to cut off since they need it to photosynthesize. If anything, maybe cut off the burnt portion of leaf while leaving what remains so the plant will still have the ability to absorb light. Hope that helps and good luck! Let me know if anything else comes up.

  • Alanna M Ponder

    Great article on leggy seedlings, thank you.

    Question,
    I started my seedlings on heat mats and lamps in my basement.
    I’m planning on transferring the seedlings when they are the right size into my greenhouse
    where I have raised beds.
    Is there a hardening off method for getting the plant used to natural greenhouse light from artificial light?

    Thank you.

    • Aaron (Mr. DeannaCat)

      Hello Alanna, yes there is a hardening off process when you bring a plant from indoors to outdoors even if in a greenhouse. We have an article about hardening off seedlings here which should be able to answer any questions you have. Hope that helps and thanks for reading!

      • Sharon

        My lettuce went leggy overnight. I need grow lights I know. But can’t get them till next year. Do you think they can be saved?
        Also have you ever tried growing in seed trays seed outside but bring them in at night?
        Thank you

        • Aaron (Mr. DeannaCat)

          Hello Sharon, I’m sorry your seedlings went leggy. It really depends on how leggy the lettuce seedlings are, it may be just as easy to germinate more seeds in case these ones can’t be saved. If you are able to get them sufficient lighting it may not be the end for them yet. I am not sure which hardiness zone you are in but if the weather is in the 60’s during the day, bringing them outside to get better lighting would be a realistic option. Just be sure to slowly introduce your indoor seedlings to the outdoors by hardening them off as to not shock them. Let us know if you have any other questions and good luck!

    • Alanna M Ponder

      Read your article and watched your video on hardening off.
      Great information, very helpful information!
      Can’t wait to get started.

      • Tracie

        Really good article on legginess! I have Dianthus seedlings that became leggy even though I had them a couple inches from the florescent lights. Don’t know what I did wrong but your information on how to fix legginess gives me hope. I just transplanted the whole peat pellet into a 3 inch peat pot. And put a fan on them like you suggested. Now I am going to mix up some water soluable fertilizer at half strength. Wish me luck! Thanks again!

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