Many gardeners begin their seeds indoors in order to control climate and to get an early start on their garden. One problem that many encounter is “leggy” seedlings. These are seedlings that are too long and think and shy on leaves. Some plants, namely most vines, are naturally like this, but when your tomatoes and bush beans look more like grapes, you probably need to change something.

Leggy seedlings are mainly an aesthetic issue for gardeners who eventually transplant the new babies to the outdoors. If it gets too out of hand, though, they can become problematic and unhealthy. This is especially true if the seedlings are to be transplanted into a garden that will have cold nights – warm enough for healthy plants, but awful cold if your stalk is too long.  So early spring planters may have issues if they’re too leggy.

What Causes Leggy Seedlings?

The main cause is light. Or lack thereof.  Seedlings are usually sprouted in seed trays or containers and are often in a window.  There’s nothing wrong with this except that the light only comes from one direction and so the seedlings that are furthest from it will grow towards it. Since the light is directional, all of the plants in the window will grow towards the window regardless. Some just have further to reach than others.

Add to this the fact that most commercial starter soils and peat pellets are heavy on nitrogen and you get a lot of quick growth as well. Much of the time, chronically leggy seedlings are a combination of soil nutrition and light issues.

How To Prevent It

Stopping legginess is actually pretty easy. Your main issue will be the light. Tilting the seedlings towards the window (propping up the tray they’re on or arranging their containers at an angle) can be a good start. Adding artificial light or a reflector (cardboard covered in tin foil, ala the cheap beach tan) to reflect light from the upper portion of the window down to the back side of the plants works as well.

Another option, if the weather is warm enough, is to keep them outside for part of the day and bring them in or keep them in on colder days. You can build a miniature greenhouse out of some old wire shelving and plastic wrap. You can also buy these pre-made and even on wheels if you really want them. (I got one from a thrift store for $10)

Finally, if your home has skylights, consider a “hanging shelf” underneath one for your seedlings. Since this light is coming more or less straight down, it’s perfect for them.

Greenhouse shelf

DIY Greenhouse Shelf