Sunday, April 10, 2016

Guide: How to avoid tall, leggy seedlings

Posted by Amanda Villaruel | |
Wondering why you have vegetable seedlings that are tall and floppy?

Oh boy, there is so much to learn about vegetable gardening :-) It is our first time growing vegetables indoors, and after a few weeks we've come to realize that growing vegetables outdoors is different from growing vegetables indoors.

When you're seed starting or growing vegetables indoors, the plants will have stricter requirements for lighting and temperature. The result that happens to many newbie apartment gardeners, is long, leggy seedlings.
Avoid spindly vegetable leggings
Avoid spindly vegetable leggings

Why care about avoiding spindly seedlings ?

The seedlings should be chubby and sturdy to survive the transplantation and to handle the outdoors climate on their own, when moved outside. If the seedlings are bending forward and not growing up straight, they are most likely suffering from insufficient light.
Harden off the seedlings and plants gradually
Harden off the seedlings and plants gradually

I tested this out and gave our seedlings some tough love by placing them on the balcony when it was sunny, but cold in the shade. When brought indoors after an hour, the seedlings seemed fine. But the next day, some of them collapsed! There were no signs of life for 4-5 days, so eventually I had to pluck them out and sow new seeds.

As I expected, it was the weakest (thinnest) seedlings that didn't survive :-(

We have repotted several seedlings over the past three weeks, and a few of them didn't survive the transplantation. They were simply too thin and too fragile to handle.

What is causing leggy seedlings?

"Let it be light"

We have read a lot about the legginess problem. If you're experiencing leggy seedlings indoors, I'm pretty sure that the seedlings are not getting enough light.

I started to sow seeds in early March and considering that I live in Norway where the days are shorter, unsurprisingly our plants haven't gotten enough light. Even if they seedlings were placed right next to the windowsill in early Spring... It's just how it is. We can't control the climate, but we can control the amount of light they can receive during the day.

Most vegetables require 14-18 hours of bright light every day.1
Seedlings and plants need lots of light to thrive
Seedlings and plants need lots of light to thrive


The higher the temperature, the more light the seedlings require. That's often the problem with growing vegetables in apartments, where the room temperature is often too high for the seedlings.

Seeds germinate well in room temperature, but after that the plants want a cooler environment. When the seedlings are appearing, it is important to place them in the light! If it's too warm and also poor light, we risk tall and weak plants.

There are different sources mentioning the best temperature for seedlings. A book I've read says that the best germination temperature for most kitchen vegetable plants is between 15-22 .2 During the organic gardening course I took this week, it was told that the seedlings should grow in temperature between 15-20 ℃. 

How do you "fix" floppy seedlings?

1. Place the seedlings outside (gradually)

The best solution would be to place the seedlings outside, with protection though if you live in a colder climate. This way you don't need to worry about the right amount of light and the right temperature.

Suggestions for protection: 
  1. You can build your own mini greenhouse
  2. Purchase a mini greenhouse
  3. Cover the plants with garden fabric
  4. Recycle a plastic bottle to make a mini greenhouse
Cover your seedlings with garden fabric in colder weather
Cover your seedlings with garden fabric in colder weather

I was worried that the plants would freeze and postponed the exposure to the outdoors climate. But then I found out that certain vegetables can handle the cold better than others. Cold-tolerant vegetables include: carrots, kale, lettuce, spinach, radishes and Swiss chard.3 It also made my day when finding out that broad beans can also grow at low temperature (4-5 ).4

Read: 10 vegetable more cold hardy than kale.
Use aluminium foil as reflector and make mini greenhouses from old plastic bottles
Use aluminium foil as reflector and make mini greenhouses from old plastic bottles

Before placing the plants outside, remember to harden them off gradually, at least a couple of days before. When the plants have accustomed to room temperature, you can ease the cold shock by placing them in the shade for a couple of hours every day for one week. After that place them outside with garden fabric.

2. Give your vegetable seedlings more lighting

  • Invest in grow light - place the light source about 15-30 cm (6-12 inches) above the plants. Any higher, the seedlings will become even more leggy.5

  • Increase the reflection of light by adding aluminium foil around the seedlings

Consider investing in plant light also known as grow light. Two weeks ago we purchased LED light specifically made for growing vegetables.

After a few days, we already saw the differences :-) The leggy seedlings that only received daylight, have now dark green leaves as opposed to pale leaves. So, now they get light during the day and after dark, an additional grow light. I sowed new seeds and the additional light has stabilized their growth and made the new seedlings shorter and sturdier, compared to their leggy neighbors.

It sounds nuts right? ;-) Well, it seems like plants prefer a different type of light than what meets the human eye, preferably in the blue and red specters. The blue light (the cool light) stimulates the seedling to grow strong, healthy stem and leaves, while the red light prompts the flowering.6
Indoors grow light for vegetable and herb seedlings
Indoors grow light for vegetable and herb seedlings

I got to say that it looked like the red light district when we turned off all the lights except for the grow light. Hahaha. My boyfriend was making jokes about the police coming knocking on our doors because inside the apartment it looks like an underground nightclub with seedy, red lighting ;-)

3. Regulate the temperature

  • Place the vegetables in a room with cooler temperature, if possible. Don't forget about the light! :-)

  • Turn off the radiator, and air the room regularly if you have them inside the apartment. Check the room temperature once in a while, and if it gets too warm, open the windows/balcony door for an hour or two. 

  • Use a (table) fan to give the seedlings a breeze. In their natural setting, plants are almost constantly in the wind. Mimicking a breeze indoors will encourage the seedlings into thinking that they should grow sturdier to withstand the breeze, which in this case comes from your fan.

    Instead of using a fan, you can also shake the plants once in a while or stroke/blow on them.

4. Add extra soil

Another thing you can try is to add extra soil around the stems of the leggy seedlings. Have you noticed the tiny hair on their stems? According to the Examiner, placing soil around the stems will work with almost every plant especially for tomato plants. The fine hairs on a tomato stem can each become a root if buried.

Continue to read:
Quick tip: sticky labels for vegetable gardening.

Urban farming project: Weeding and sowing lettuce seeds.


Have your say about what you just read :)

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