What causes leggy seedlings?

Sometimes, despite your best efforts, seedlings germinate into weedy leggy specimens. The seedling has a long stem which can be floppy and altogether it looks a bit hopeless. This often happens when seeds are germinated early in the year. It is caused by less than ideal growing conditions, usually low light levels or light from one source.

All seedlings will grow towards light. Early in the year,  seedlings are usually germinated inside, on a window sill, an indoor porch, or conservatory. The problem is that the light comes predominately from one direction, unlike outside or in a greenhouse where it is 360 degrees.

The seedling naturally gravitates towards the light and this causes it to pull towards the light source, which in turn can make for a leggy seedling.

All is not lost as sometimes this can be salvaged. 

What to do about leggy Seedlings

New Video The Sunday Gardener What to do About Leggy Seedlings

Leggy seedlings have long stems which look thin, and floppy. Your first thought maybe to bin them and start again. It is worth thinking again as it is an effort, and cost to germinate and disheartening to start again. Also, some veg seed packets, especially the large seeds such as cucumbers and the F1,  only have a few seeds 

It is sometimes possible to salvage weedy seedlings, and worth a try. Wait until the seedlings are large enough to handle and can be potted on. When replanting the seedling, sink it low into the new pot so that most of the leggy bit is below the soil surface. If you like, bury the mistake and often the seedling with grow on with no obvious problems.

Look at the series of images below.

The first image is of the leggy seedling, it's a courgette, and of a size that it can be potted on. Instead of putting it into the shallower pot, which may be the usual choice , in the second image, (grey pot) select a pot with greater depth. The next 3rd image shows easing the seedling out of the container it germinated in, and its healthy the root system is starting to establish, it is just a bit  leggy.  

The last image shows the seedlings potted deep into a container with only a little of the stem above the soil and it looks better. Give it a couple of weeks and it should grow on fine, if should it fail you have lost little other than some time and compost.

This method is particularly effective with tomatoes, which like to be re potted deep to encourage the root system and almost always grow on well after this treatment.

More information about How to Sow Vegetable and Flower Seeds

and 10 top tips on How to Germinate Seeds

weedy seedling

This is a weedy courgette seedling which is floppy and not ideal in its present state

Choice of containers

Choice of containers

Choose a deeper container for re potting. Not the shallow grey pot but the one on the right with more depth.

Easy the seedling out

Easing a delicate seedling

Gently ease the seedling from its container, handle by the leaves, not the stem.

Courgette seed re potted

courgette seed re potted

Here is the final product. The courgette seed has been repotted, deeper into the container, much of the leggy stem has been buried and it went on to grow into a sturdy plant.

last updated 08.10.2021