How to Thin Indoor, Outdoor and Container Seedlings

One of the most difficult gardening tasks I have found is thinning seedlings. It is not a hard job, just frustrating and tedious. Frustrating, because I have to make the careful decision of which seedlings to keep and which ones to discard. If I make the wrong choice, I could be left with a plant that produces very little or nothing at all. Tedious, because the seedlings are delicate, so I have to take my time in order not to damage them during the thinning process. If seedlings are growing close together, it is very easy to damage or remove more than you planned on.

Why Thin Seedlings?

Whether you start your seeds indoors or straight in the garden, you will need to do some thinning. Even if you space your seeds according to the recommended width, getting 100% growth is almost impossible. You are bound to have some bare space in between plants. Seedlings that are grouped too close together compete for light and soil nutrients as well as space. Thinning ensures the seedlings will have plenty of room for hardy root development and plant growth. It will help maximize crops, with the production of larger vegetables and flowers.

Steps for Thinning Indoor Seedlings

-Choose your seedlings carefully. You want to be sure you keep the healthiest and strongest looking plant in each cell pot. Look for and keep seedlings that are growing straight, have strong stems, and unblemished leaves.

-When you have chosen the least desirable seedlings, use small, pointed scissors to snip the seedlings near the top of the soil.

-If I cannot make a decision because all the seedlings prove to be strong, I will use bamboo tweezers to pull them gently from the soil and plant them in another pot. If you do this, you have to be careful that you do not damage the roots.

NOTE: Removing seedlings with tweezers instead of cutting them can leave the soil around the roots of the remaining seedlings loose. Be sure to add water to redistribute the soil.

Thinning Outdoor Seedlings

Thinning outdoor seedlings is similar to thinning indoor seedlings. The only difference is when you thin indoor seedlings you will leave one seedling in each cell of a seed tray, compared to outdoor seedlings, which you will thin according to the recommended spacing on the planting guide or the back of the seed packet.

One other thing that is different between thinning indoor and outdoor seedlings is that outdoor seedlings tend to be a little more mature; in which case you can eat them, such as tender baby lettuce and spinach leaves.

Thinning Container Seedlings

With the limited space in container gardens, it is even more important to thin seedlings. Seedlings growing in container gardens can quickly become overcrowded and die, as they compete for light, water, soil, and nutrients. Sometimes I find myself having to thin the seedlings in my container gardens after I have transplanted them from the small cell pots where I had already thinned them. It is very easy to over plant small seedlings in containers because they can look small in a large space. When planting seedlings in a container, try to envision how those seedlings will look when they are fully-grown plants.

Thinning seedlings may be a frustrating and tedious task, but for me it is well worth the trouble especially when I have large, juicy tomatoes and crisp lettuce on my dinner table.

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Sources: Personal Experience, The New Victory Garden, by Bob Thomson