In this article, I will focus on seedlings that have been started indoors. I like to call my process the ‘survival of the fittest’ approach to thinning seedlings. Using this approach, I thin out the weakest seedlings. Seedlings that are either too tall (leggy) or too short (stunted) are good candidates. Or seedlings that don’t look as healthy as their peers.
Estimated reading time: 4 minutes
No one really likes to thin. Not because the process is difficult but rather because it’s hard to dispose of plants that we have taken time to grow. Ok, you just need to get over that. Seedlings need to be thinned to reduce competition for resources. Leaves and roots need space to grow and flourish. In addition, seedlings need nutrients, moisture, and light.
Now, we all use different containers to plant our seeds. Therefore, it is useful to understand how I plant my seeds. When I plant seeds, I use individual seed trays that have 12 cells/tray. In each cell, I plant from 1-3 seeds. If I am planting seeds that I have saved, then generally I plant 3 seeds per cell. Otherwise, I use 1-2 seeds per cell. With this approach, I always have seedlings that need to be thinned.
When using the individual cell method, it’s generally recommended to thin so there remains one plant per cell. However, if you use a large container to plant seeds, then the distance between seedlings should follow the guidance for spacing on the seed package.
Lastly, if I still have more than one healthy seedling per cell, I will ‘pot up’ the seedlings. In other words, I replant the remaining seedlings in a larger container of their own. Yes, I must admit that I strive to keep as many healthy seedlings as possible.
Things you need
- Scissors
- Seedlings
How to thin seedlings?
- Wait for the seedlings to have two sets of true leaves
- Choose the seedlings to thin
- Tall leggy seedlings are a good choice for thinning
- Seedlings that are smaller than the others (stunted)
- Seedlings that don’t look healthy
- Using a scissor, cut the stem of the seedling to be thinned a soil level
Thinning examples
The examples below were planted 5 weeks ago. They all have at least two sets of true leaves and are ready to be thinned.
The first example is cosmos seedlings. In the picture, I have noted the seed leaves and the true leaves. Remember the true leaves resemble a fully mature cosmos. In each cell, there is more than one seedling. In a couple of cells, there are three seedlings. We will thin out the cells with three seedlings. Notice, the seedlings in the cells with three are stunted in their growth. Therefore, these are good candidates to thin out.
The second example is profusion zinnia seedlings. Profusion zinnia is a low-growing zinnia. In the example below, there are a couple of problems. First, there are two seedlings that are leggy. Leggy seedlings are good candidates for thinning. Second, there is one cell with four seedlings. This is too many for such a small cell. Crowded seedlings are candidates for thinning.
The third example is tall zinnia seedlings. Yes, I love zinnia. In the example below, we see a few cells in which three seedlings are growing. This is too many for such a small cell. One of the three seedlings should be thinned.
That’s all there is to the survival of the fittest approach to thinning seedlings. Hope you enjoyed the article. I am off to potting up my seedlings now.
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