Thinning seedlings - 28. April 2020

Thinning seedlings is important in order to avoid overcrowding and to give plants enough space and nutrients to grow stronger. Thinning seeds also helps to avoid fungal infections, by improving the flow of air around plants.

Why not sowing directly the seeds at the desire space? 
When sowing seeds we don't always get 100% germination and we can end up having large spaces between one plant and another.  


Seedlings must be thinned early enough, before the roots get intertwined, if this happens, the remaining seedlings might suffer from root disturbance. 
Most seedlings are thinned out when they are between 5cm and 7cm and when they have a couple of leaves. 
Damping the soil before thinning, makes it easier to pull the plants our intact and avoiding damage to neighbours. It's a good idea to do the thinning in the evening as the remaining seedlings will have a better time recovering from the stress they may have received. 


Unwanted seedlings, have to be gently pulled out of the soil. Some species, like root crops, are more sensitive to thinning, due to the fact that disturbing the roots while young might cause deformation, therefore they should be pulled out with extra care, or even better they can be cut at the soil line. 


The optimal space varies according to different plants, the rule of thumb is to leave about 5cm between each seedling. 

Vegetables that need to be thinned out and typical spacing are the following:

  • Beets (8- to 15-cm spacing)
  • Carrots (5- to 8-cm spacing)
  • Lettuce (45- to 60-cm spacing)
  • Onions (8- to 12-cm spacing)
  • Parsnips (8- to 15-cm spacing)
  • Radishes (5- to 8-cm spacing)
  • Rutabagas (20-inch spacing)
  • Spinach (5- to 15-inch spacing)
  • Turnips (5- to 10-inch spacing)