Thinning out seedlings

Why thin out seedling rows?

The purpose of thinning seedlings is twofold:

1. Spacing plants: It can sometimes be difficult to sow the right amount of seeds, especially when they are fine, like carrot or radish seeds. Thinning allows you to space out future plants so that they all benefit from sufficient room. This is essential, as overcrowded plants would compete and have to share insufficient resources.
2. Selecting the strongest specimens: Seedlings do not all display the same vigour. By removing weaker plants, you encourage the most robust ones, which will develop into resilient plants.

How to thin out seedlings?

Thinning should be carried out when the plants are somewhat developed, at the 3 or 4-leaf stage. This is done by hand, in one or two steps, preferably on humid days, and watering at the end of the process.

During thinning, you can:

• simply remove the plant by cutting it at the base,
• relocate and replant it elsewhere if the plant tolerates transplanting (this is not the case for Apiaceae, such as celery or carrots, generally),
• consume them as “microgreens,” as with salad leaves, for example.

How to prevent or limit thinning of plants?

Although thinning is useful, it can be tedious. To avoid or at least minimise it, we recommend:

• mixing your seeds with sand or dry coffee grounds to sow more thinly,
• using a precision seed sower,
• opting for seed tapes where seeds are pre-spaced. To learn more, how to make a seed tape?