Thinning simply means removing some plants so that the remaining plants have enough space to grow.
In the photo above you will notice there are multiple seedlings per cell. In the video below we will show you how we thin seedlings like this in the Teaching Garden.
In trays, we thin seedlings to one plant per cell or pot. Proper space is important for healthy plants; seedlings growing too close together will compete for resources. Thinning also helps improve air circulation, an important factor in reducing plant diseases.
When is the right time to thin seedlings? If you plan to cut or pinch them, rather than attempt to separate, the earlier the better! The sooner you thin your seedlings, the sooner the remaining plants will benefit.
How do you choose which seedlings to keep?
Look for the strongest, healthiest plant in each cell. Cut away all of the surrounding seedlings in that cell by snipping at the soil line. A strong, healthy plant has a relatively thick stem and is compact – not lanky or ‘leggy’. If you are having trouble deciding, that means all of your seedlings are relatively healthy and it doesn’t matter which one you choose to keep! Sometimes slight size differences are simply due to a slight difference in germination time, not necessarily health of the plant.
You can apply the same practice to crops directly seeded into the garden.
The thinned seedlings from many crops are edible – in fact these are #microgreens. If you are thinning lettuce, spinach, bok choy, radishes, mustard greens, kale, cabbage, or collard greens – just to name a few – you can munch on them, use them to boost a salad or garnish a dish.
Since we recommend using 1-2 seeds per cell for most seeds, chances are you started more seeds than you can plant out. The easiest way to thin seedlings is simply to snip or pinch off the smaller plants in each cell, leaving one per cell.
Later this month we will share with you how to pot up your seedlings, during this time you can separate out crowded seedlings into different pots to keep them all for planting. At the Teaching Garden, we usually separate and pot up hardier plants such as tomatoes, peppers, eggplants, and leafy greens like swiss chard and kale – if you are growing any of these from seed, keep caring for your seedlings and keep an eye on this space for your next steps!