It seems to happen every year; my tomato seedlings bolt for the sky. Of course, this means I end up with tall, leggy seedlings. Leggy seedlings are less likely to grow into strong, producing plants. They are more apt to flop over when the leaves get big, or break when transplanting in the ground. They are delicate and tend to die before they get very big. Luckily, I have finally figured out how to fix the problem.
Update: Within minutes of posting this article, several people contacted me with the “leggy seedling” fix – keep a light over the seedlings, but only about 6 inches away. That way they won’t grow too fast as they stretch towards the light. This method absolutely works for most people, but I have never had good luck with it. I write more about it in this old post, 5 Tips for Growing Tomatoes from Seed, or this one, Starting Tomato Seeds Step-by-Step. Hopefully when you follow this technique it works for you. But, if you – like me, have a talent for growing leggy seedlings, read on!
Peat Pots: The Good and the Bad
Peat pots are inexpensive, convenient, and available almost everywhere. But they are not always the best option when starting seeds. They seem to promote quick, leggy plant growth. They dry out quickly, and they get soggy quickly – putting seedlings at risk of drying up or drowning. So, you have to constantly care for the seedlings – no vacations allowed until the plants are bigger!
Despite this, I almost always use peat pots when starting my numerous tomato plants (this year only 20!). I have used empty milk containers, soil plugs, seed starter trays, and several other options, but for me, the peat pot convenience factor outweighs the constant care factor. And yes, my seedlings are always leggy. Here’s how I keep them from dying before their time:
Blowing in the Wind
As soon as seedlings have leaves, I subject them to a light breeze. Not outside, but on the windowsill. I use a clip-on fan, set it on the lowest setting, and let the wind sweep over the seedlings. The light, but constant, movement makes the stems tougher. As you can see on the photo, it produces little hairs on the stems. You can almost watch them get thicker during this process.
Keep the fan going for at least 8 hours a day, for a couple of weeks, or until each seedling has at least two sets of leaves.
Time to Transplant
As soon as each seedling has two sets of leaves, I transplant the peat pots. Many experts recommend snipping off the extra seedling in each pot at this point, but I don’t do that yet. First, place about ½ inch of gravel in the bottom of a clear, plastic drinking cup. To transplant, gently move the peat pot and seedling and place it in the cup. Carefully add potting soil all around the seedling.
Covering much of the stem with soil lets additional roots develop (from the stem), making the future tomato plant stronger. I use clear cups so I can see how damp the soil is. Often the top will dry out, but there is still plenty of water lower. The clear cup helps stop me from over watering the seedlings.
The seedlings, now in a cup, go back on the windowsill. I let them sit and get sturdier for a few days. Then I snip off all the extra seedlings, leaving just one seedling in each cup. Now the fan goes back on, continuing to strengthen the stems.
Into the Ground
When it is time to move the plants to the ground, I still am cognizant of those early leggy seedlings. I either dig the hole very deep and place the plant in the soil almost up to its leaves, or I dig a trench and plant the stems horizontally. This gives the plants another opportunity to develop additional roots, leading to baskets of beautiful tomatoes!
Your seedlings are leggy because they are having to reach too far to get enough light. Put them under a shop light that you can raise and lower. After your seedlings emerge, gradually adjust the light to account for the increase in height of the seedlings. Be sure to stay just above the seedlings. This should improve your seedlings tremendously. I have been growing mine this way for over 40 years.