How to Thin Vegetable Seedlings

Teenage girl planting seedlings
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Growing vegetables from seeds is much less expensive than buying nursery seedlings, but it's also slightly more work. Many vegetable seedlings are very tiny, and they are sown simply by sprinkling the seeds in loose rows along the soil. As they germinate and sprout, the seedlings are very tightly spaced, and a routine duty for gardeners is to systematically pluck out enough seedlings to allow the remaining plants plenty of room to grow. Plants started in pots are usually not a problem because you can separate them when it's time to transplant outdoors. Plants that are direct seeded in the ground and especially seeds of root vegetables are another matter. These plants almost always require thinning.

Fresh Arugula plant in soil
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Benefits of Thinning Vegetable Seedlings

Thinning seedlings produces healthier plants and higher yields by:

  • Allowing room for proper growth
  • Reducing competition for water and nutrients from nearby plants
  • Allowing for good air circulation between plants

Some larger seeds, like radishes and parsnips, can be spaced at planting, but you don't always get 100 percent germination and you could wind up with spaces within your rows. Some seeds may look large, like as those for beets, but they are actually little clusters of seeds. Even if you optimally space these seeds when planting, it will still result in overcrowded seedlings. Some gardeners will crush the seed clusters into individual seeds and plant those, but that's frankly more work than thinning out the extra seedlings.

When to Thin Vegetable Seedlings

Seedlings are usually thinned once they have one to two sets of true leaves. Most will be 2 to 3 inches tall by then and easy enough to grasp and pull. However pulling the unwanted seedlings often brings up all the neighboring seedlings, even the ones you wanted to leave growing. It is easier to snip the extras at the soil line. This also keeps them cleaner and ready to rinse and toss in a salad.

If you prefer to pull your extra seedlings, thinning while the soil is damp will help you pull just the excess plants while leaving the ones you want to keep. It won't work every time, but it does make it easier to slip them out of the soil without turning up everything nearby.

Thinning in the evening gives the remaining plants a chance to adjust before being exposed to heat and sunlight. Disturbing the soil also disturbs the roots, so make sure the soil is moist and try not to thin on a hot, sunny day.

Project Metrics

  • Working Time: 30 minutes (for a 20-foot-long row)
  • Total Time: 30 minutes
  • Material Cost: None

What You'll Need

Equipment/Tools

  • Kneeling pad (optional)
  • Garden scissors or nail scissors (optional)

Instructions

  1. Determine Desired Spacing

    Vegetable seed packets will give recommendations on the spacing between plants, which can be followed for thinning. In general, leave the anticipated size of the mature vegetable plus a couple of inches on either side. Your seed packet will list optimal spacing. Vegetable plants that need thinning and typical spacing recommendations include:

    • Beets (3- to 6-inch spacing)
    • Carrots (2- to 3-inch spacing)
    • Lettuce (18- to 24-inch spacing)
    • Onions (3- to 5-inch spacing)
    • Parsnips (3- to 6-inch spacing)
    • Radishes (2- to 3-inch spacing)
    • Rutabagas (8-inch spacing)
    • Spinach (2- to 6-inch spacing)
    • Turnips (2- to 4-inch spacing)
  2. Remove Unwanted Seedlings

    There are two ways to remove seedlings: plucking them by hand or snipping them off with scissors. Long rows of vegetables can entail a lot of hands-and-knees work, so a kneeling pad is a good accessory.

    Seedlings are easily plucked out with your hands, simply by gripping them between thumb and forefinger and tugging. This can be easiest when the soil is moist and pliable; lightly watering before you thin can be helpful.

    If you prefer to avoid disturbing the soil by pulling seedlings, then you can simply snip off the unwanted seedlings by cutting them off at ground level. Any scissors will do, but for very fine work and tiny seedlings, fingernail scissors are a great tool.

  3. Water the Survivors

    Thinning can disturb the soil, so it is best to lightly mist the vegetables after thinning, which will rejuvenate the remaining plants.

  4. Thinning by Rake (Optional)

    If you are growing vegetable seedlings in blocks rather than rows, you can try simply running a flexible rake through the seedlings. Plants won't be perfectly spaced, but it will open up more space for them to grow and is much faster than plucking or snipping off seedlings by hand.

  5. How many seedlings you thin out—and the spacing you allow for the remaining seedlings—will depend on whether you want your vegetables to grow to full size or eat them early. For example, if you like to harvest and eat tiny carrots, you can leave the seedlings rather tightly spaced, but if you prefer to harvest large carrots at the end of the season, the spacing should be much further apart.

    A man planting and watering lettuce seedlings
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Tips

  • Root vegetables, like onions, beets, and carrots, can be more sensitive to thinning because disturbing the roots while young can cause deformation. Transplanting long rooted vegetables, like carrots and turnips, will cause them to fork. Pull one seedling at a time or try cutting the unwanted seedlings at the soil line, instead of pulling.
  • Some people find it difficult to sacrifice so many vegetable plants. Some seedlings, including lettuce, beets, and spinach, can be harvested and the greens tossed into your salad at any time, so all is not lost.