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What To Do With Leggy Seedlings

What To Do With Leggy Seedlings

At this time of year we get frequent calls from people who have started seeds inside and find that they’ve gotten too “leggy.” This is most common for those who are growing seedlings on a windowsill where the light might be strong but not as direct or constant as you’d find in a greenhouse. The problem is, of course, that once the seedlings get lean and spindly they are more likely to be damaged when planted outside. Here are some of the reasons that seedlings get leggy, and what you can do if this has happened to you.

  1. Seedlings grow leggy when they are reaching for the light. Be sure to grow your plants in as much light as possible. If you’re growing under artificial lights such as fluorescent or the long, tube gro-lights, position the bulbs only about 3″ from the tops of the plants. Most people rig up a system where the lights can be raised as the seedlings grow.
  2. Seedlings also grow leggy when they are started too early. Be sure to use the end of May as the time when most summer plants can be placed outside and work backwards from there, using the germination times on the seed packets. So for plants such as zinnias, for example, that germinate and grow quickly, they shouldn’t be started before the end of April.
  3. Once seedlings get too long and leggy many wonder if they can sink the stems lower in the soil once the plants are put outside. This works for tomato plants but most others can’t be sunk into the ground in that way. Instead, use the methods below to help strengthen the plants.
  4. Don’t over-fertilize! Many people mistakenly believe that fertilizer will make plants stronger. In reality, fertilizers make plants grow larger and faster but they don’t help the plants to become sturdy. Keep synthetic fertilizer to a minimum until the plants are growing outdoors.
  5. Environmental “stresses” such as wind stimulate hormones in plants that signal the roots and stems to grow strong. So putting a small fan next to your seedlings on a timer so that the plants are blown in the breeze for a couple of hours a day will help strengthen leggy plants. Gently passing your hand over the tops of seedlings a few times every day will also stimulate stronger growth.
  6. When it’s time to move the plants outside introduce them to the “real world” gradually. Don’t put tender plants out into the direct sun – either place them in mostly shade (the dappled sun through trees is good) for a few days or put them outside during a stretch of cloudy weather. If the weather turns stormy, pull those plants inside until heavy rains and high winds pass.
  7. Most leggy plants become sturdier once they are growing outside.

    Sometimes people are tempted to fertilize tiny tomato seedlings in order to hurry their growth in the spring. Don't do this too early or you'll end up with taller, weaker plants before it's time to plant them outside. Tomatoes shouldn't be planted outdoors until the night time temperatures are reliably above 50 degrees.

    These broccoli seedlings are short and strong because they have been raised in a greenhouse where there is lots of light. Seedlings are more apt to become leggy when the light isn't strong enough. If your windows don't get full sun, consider starting your seedlings under lights that are placed about 3" from the tops of your plants. (Note: high-powered grow lights that get hot can be further from seedlings, but fluorescent tubes, regular or full spectrum, should be close to the plants.)

17 Comments

  1. J Reynolds on April 6, 2016 at 3:39 pm

    Thanks! I have some leggy okra and one leggy zinnia. I still have time, but didn’t know whether to start over or try and correct them.

    • CLFornari on April 6, 2016 at 5:33 pm

      If you’re on Cape Cod you should start over with the zinnias – the okra too if there are a lot of them. If there are only a few, transplant them to larger pots and grow them on indoors. On the Cape you can’t plant these out until the end of May, and by that time the zinnias might not only be even more leggy but have mildew as well. Zinnias are best started about three to four weeks before planting outside, so the end of April in this area.

  2. Marianne Vaudreuil on April 21, 2016 at 9:26 am

    How do you keep to to plants from getting too leggy? Can they be cut down so this won’t happen?

    • CLFornari on April 21, 2016 at 12:12 pm

      Marianne,
      There is no one way to prevent leggy plants – some get leggy because they aren’t in enough light (reaching for the sun) and others because they have been given too much water and fertilizer, or are growing close to other plants so are trying to out-compete them. Some plants just get leggy because it’s in their genetic makeup to do so, and some get this way as they age. If you cut some plants down (most perennials) they will grow back shorter in the same season but other plants (lavender, for example) will die when cut back hard. So it’s impossible to give you advice unless we know what plant you’re talking about. Come into the store and we will steer you in the right direction.

  3. Norma McL on March 10, 2018 at 6:45 pm

    May I simply note that I very much like your no-nonsense style? All of us gardeners–very experienced ones included–sometimes need specialized help, but the advice is frequently so watered down with social baggage that one has to sift through what the adviser said for politeness’ sake to read what wasn’t and is truly helpful. I am not saying you’re impolite. I am saying that I prefer my advice straight up and direct, and you seem to give good advice.

    When you really need help, you don’t require that the helper curtsy.

    • CLFornari on March 11, 2018 at 1:06 am

      Norma – what a lovely comment. Thanks for taking the time to write, and I’m glad you appreciate our blog and the way it’s written. We’ll continue to serve our advice straight up…although we might occasionally garnish “with a twist.”

    • Dolly on April 21, 2018 at 1:42 pm

      Excellent comment

  4. Amy B on May 30, 2018 at 6:22 pm

    Hi! With leggy tomato seedlings, should I replant them (deeper) in seed starter soil, or into regular soil, before I put them in the garden? Thanks?

    • CLFornari on May 31, 2018 at 1:37 am

      Amy,
      If the night temps are above 50 where you are, and the plants have been hardened off by a few days outside in part-shade, then just plant them directly into the garden and bury the stems so about 1/2 of the plant is in the soil. Once the soil and air temperatures are warm they will take off and grow strong.

  5. Tom on September 12, 2018 at 7:29 pm

    I have potted zinnias that have become leggy over the summer. I cut back each wilted flower to the 3 leaf stem below it but it seems if I cut back 6 inches, it grows out 9 inches (example) and by summer end they are leggy and weak stemmed. I’d like to drive bushier, shorter stalks but not reduce flower production. Is this possible?

    • CLFornari on September 12, 2018 at 8:42 pm

      Tom,
      Part of what you’re seeing is genetic. I think you have the wrong zinnia for your pots. If in the future you plant Profusion zinnias you’ll find that they stay round, bushy and flower-filled. Profusion can easily be grown from seed, and many garden centers sell them in six packs.

  6. Gayle O’Brien on March 24, 2019 at 11:45 pm

    I’m in NE and it’s still very cold. My seeds just popped up and they are leggy. Can I transplant into deeper pots even being so tender.
    Or should I just let them stay under the light?

    • CLFornari on March 24, 2019 at 11:48 pm

      Gayle,
      Let them stay under the lights but be sure those lights are only 3 or 4 inches above the seedlings. Also, put a fan on them to simulate wind – on a timer so that the seedlings get stimulated by the breeze for two or three house a day. And don’t fertilize as this makes the seedlings grow faster but weaker – wait for fertilizer until you plant them outdoors.

      • John A Gallicano on April 9, 2019 at 9:23 pm

        thanks for your great advise on leggy seedlings john G.

  7. Stina on April 13, 2019 at 6:17 pm

    Agreed on the straight up no nonsense presentation! Usually I have to dig through so much fluff to get answers.

  8. Barbara on April 17, 2019 at 6:59 pm

    if they are already starting to fall over, can I save them. Mostly sunflowers

    • CLFornari on April 17, 2019 at 7:07 pm

      Barbara,
      Yes – use the tips at the end of this post about not fertilizing, exposing to wind etc. On days when it’s above 50 degrees put them outside, but start by putting them out in the shade and only for an hour or so. Introduce them to more time and direct sun gradually. (Note: in the future, sunflowers are best planted directly into the garden once the danger of frost is past.)

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