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How to Thin Out Seedlings

Last Updated: May 26, 2020 References

This article was co-authored by Lauren Kurtz. Lauren Kurtz is a Naturalist and Horticultural Specialist. Lauren has worked for Aurora, Colorado managing the Water-Wise Garden at Aurora Municipal Center for the Water Conservation Department. She earned a BA in Environmental and Sustainability Studies from Western Michigan University in 2014.

There are 12 references cited in this article, which can be found at the bottom of the page.

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Seedlings must be thinned out to grow into healthy and strong adults. Although it can feel wrong to remove healthy plants, this prevents fungal and growth problems later on. Creating enough space between the plants lets each seedling get all of the sunlight, water, and nutrients it needs. Wait until the seedlings are 2–3 inches (5.1–7.6 cm) tall and choose a mild day to start thinning them out. Properly spaced plants will help your garden be fruitful and thriving!

How to Thin Out Seedlings. Seedlings must be thinned out to grow into healthy and strong adults. Although it can feel wrong to remove healthy plants, this prevents fungal and growth problems later on. Creating enough space between the…

How to Thin Vegetable Seedlings

  • Total Time: 1 hr
  • Skill Level: Intermediate
  • Estimated Cost: $0

Growing vegetables from seed is much less expensive than buying seedlings from a garden center, but growing from seed also slightly more work. To save time and effort, many gardeners sow vegetable seeds—especially seeds that are very tiny—simply by broadcast sprinkling them in garden beds rather than sowing each seed individually. As a result, too many seedlings sprout and are packed too closely together.   When this happens, gardeners must systematically remove the extra seedlings to provide enough space for the remaining seedlings to grow. Thinning seedlings produces healthier plants and higher yields by reducing competition for water and nutrients and providing good air circulation between plants. Follow these few simple steps to thin seedlings.

When to Thin Vegetable Seedlings

Seedlings are usually thinned when they have one to two sets of leaves. Most plants will be 2 to 3 inches tall by then making them easy enough to grasp and pull out.   If you prefer to pull your seedlings rather than cutting them with scissors, thinning while the soil is damp will make it easier to slip them out without disturbing everything nearby. In addition, thinning in the evening gives the remaining plants a chance to adjust before being exposed to heat and sunlight.

What You’ll Need

Equipment / Tools

  • Kneeling pad (optional)
  • Garden scissors or snips (optional)
  • Flexible rake (optional)

Instructions

Determine Desired Spacing

Seed packets will usually provide appropriate guidelines for seed sowing depth and spacing. In general, plants should be spaced based on their mature size plus a few inches. Here are spacing recommendations for a few commonly grown vegetables:

  • Beets: 3 to 6 inches
  • Carrots: 2 to 3 inches
  • Lettuce: 18 to 24 inches
  • Onions: 3 to 5 inches
  • Parsnips: 3 to 6 inches
  • Radishes: 2 to 3 inches
  • Rutabagas: 8 inches
  • Spinach: 2 to 6 inches
  • Turnips: 2 to 4 inches

Remove Unwanted Seedlings

Seedlings can be easily plucked with your fingers simply by gripping them between your thumb and forefinger and giving a gentle tug. This method of removing seedlings is easiest to do when the soil is moist and pliable. If you prefer to avoid disturbing the soil (and nearby plants), you can use garden scissors or snips to cut off the unwanted seedlings at ground level.

Thinning long rows of seedlings requires bending and working close to the ground. Thus, a kneeling pad can be a helpful tool to keep you comfortable.

Thin by Rake (Optional)

If you are growing vegetable seedlings in blocks rather than rows, you can run a flexible rake through the seedlings to thin them out. However, the seedlings won’t be perfectly spaced. Raking will free up more space for remaining seedlings to grow and is much faster than plucking or cutting seedlings by hand.

Water the Survivors

Thinning can disturb the soil, so it’s best to lightly mist the remaining seedlings after thinning to rejuvenate the plants.

Tips for Thinning Vegetable Seedlings

Seedlings started in pots usually don’t have to be thinned because you can separate them when it’s time to transplant them outdoors. However, seeds that are directly sown into the ground almost always require thinning.

How many seedlings you take out—and the spacing you allow for the remaining seedlings—will depend on whether you want your vegetables to grow to full size or if you prefer to eat them early. For example, if you like to harvest tiny carrots, leave the seedlings tightly spaced. But if you prefer large carrots at the end of the season, the spacing should be much farther apart according to the directions on the seed packet.

Root vegetables can be sensitive to thinning because disturbing the young roots can cause deformities. Also, transplanting long-rooted vegetables, such as carrots and turnips, can cause them to fork. So, to thin root vegetables, carefully remove one seedling at a time, either by gently pulling it from the ground or cutting it at ground level. That way, you shouldn’t disrupt the remaining plants.

Finally, some gardeners find it difficult to sacrifice so many vegetable plants. The good news is that some plants—like lettuce, beets, chard, and spinach—is that you can toss the tiny seedlings you remove into salads or other recipes, so all is not lost.

Seeds often sprout too close together and need to be thinned to have space to grow. Learn when and how to thin seedlings.