Your Questions Answered: Tall and Floppy Seedlings

Question: I bought an all-in-one seed starting kit that is supposed to make the procedure a breeze. I’m new to this so I tried growing stuff like marigolds, pansies, and herbs but everything died! The seedlings grew tall and floppy with a couple of sad looking leaves. I propped them up but after a few days they gave up and “met their maker” so-to-speak. Can you give me some advice so I can see where I went wrong?

If your seedlings are growing tall and floppy it probably means they aren’t getting enough light. Light deficient seedlings grow tall, thin, and eventually weak as they reach towards the closest light source. This leads to sickly plants that are susceptible to the kind of disease that eventually carried your seedlings to plant heaven. In their early days, most seeds require heat rather than light to get the ball rolling. However, your seedlings will need plenty of strong light — at least 12 to 16 hours per day — once they have popped out of their shell and up through the soil.

Finding a good spot in your home can be tricky. A south-facing window will do during bright summer months, but even springtime sunshine lacks the consistently intense light that seedlings depend on.

An inexpensive fluorescent light is the best way to ensure the right start for your young flowers and herbs. Don’t break the bank on a swanky greenhouse system. Instead pick up a cheap and practical fluorescent shop light box with two fixtures (fits two tube bulbs) from your local hardware store. Get 40-watt bulbs; one cool white and one warm white and suspend the box about 4″ above your plants. Hang the light on a linked chain so you can raise it as your seedlings grow.

This setup isn’t exactly stylin’ (unless science-geek chic is your thing), but your next round of seedlings are bound to be robust, stocky and ready to make the journey outdoors.

Get It: A 4 ft shop light with built-in chain will cost around $25. at your local home improvement store. I recommend Phillips Alto T12 or T8 bulbs (about $2.50 each). Make sure your bulbs are a match for the fixture as the two aren’t interchangeable. A setup with T8 bulbs will be a slightly larger investment but are about 20% more energy efficient.

Gayla Trail
Gayla is a writer, photographer, and former graphic designer with a background in the Fine Arts, cultural criticism, and ecology. She is the author, photographer, and designer of best-selling books on gardening, cooking, and preserving.

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17 thoughts on “Your Questions Answered: Tall and Floppy Seedlings

  1. This could also be a lack of air circulation. If you don’t have air circulating your seedlings will do exactly what yours did.

  2. uh oh, i recently bought this all-in-one 25″ light fixture from canadian tire that is labelled “plant & acquarium bright stik” but it only has one bulb. it says it’s 34 watts, and gives off 470 lumens. is this not bright enough? should i return it and get what you suggested?

  3. Some of my seedlings are quite leggy, but seem to be doing ok for now. When it comes time to plant (I’ve only just started hardening off) should I plant them deeper to give the stems more support? I figure the morning glories will be ok (they’re morning glories, after all), but what about things like agastache & matthiola which should end up at about 16 – 20 inches high? Should they go deeper into the ground, or will gently attaching them to toothpicks in a whacked-out liliputian staking scheme do the trick?

  4. My sunflowers got leggy before I figured out 75 watt compact fluorescent bulb only = 20 watts. I put them out two days ago and they’re flopping all over the place, but very much alive and growing new leaves. I only started them indoors so the sqirrels wouldn’t dig up the seeds. I hope they straighten out or I’ll have a horizontal garden this year!

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  6. thanks for this QA. I always wondered why I had such trouble starting from seeds. The advice is too late for my poor Rosa dumalis seeds (which is really a shame since those were really hard for me to come by) but I’ll be either starting seeds out on the porch or under a full spectrum light from now on. The south-facing window apparently wasn’t enough.

    I’m also interested in the question asked upthread about whether one should plant leggy seedlings deeper to provide support and with the hope that (like tomatoes) the buried stem will just turn into roots.

  7. Cabin fever prompted me to start my seeds too soon this year. Now winter’s returned to CT. and my house is overrun with planters. Any tips to keep plants happy while we wait for spring?

  8. So, you say that they need 40 watts, but then you also say that T8 are ok too.. but T8 bulbs are only 32 watts, aren’t they? Or is that just mine? Is 32 watts sufficient?

    Thank you for posting this! Much needed info!

  9. I use APS seed starter kits to start all our garden seeds. At times, I have 10 going at once. I bring them out during the day and if it’s going to be cold, I bring them in the house or garage at night. I place next to the wood siding on the southside of our deck. The seedlings love it. I’ve been doing it this way for many years and have always had great success. The seedstarters are maybe 10″ x 12″ and are very lightweight.

  10. Raine: The T8′s are fine. They are energy conservers but still make enough light.

    Katie: Are you living in a warmer climate? In Toronto the temperatures during seed-starting season are often below freezing so any outdoor keeping isn’t possible.

    Rosemary: Try and get as much light for them as possible. A south-facing window, some extra lights if you can. I can’t speak to it quite yet but I am testing out a compact fluorescent grow bulb from Sylvania that was affordable and screws into a clip-on floodlamp housing.

  11. Rosemary: I forgot to mention that you might need to repot them to larger containers. Depends on the plant and the containers you’ve got them in now.

  12. I’m in Tennessee (US zone 7). And no, seedlings wouldn’t be outside in your kind of weather! I’m fortunate to have warmer temps for the seed starting season.

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