How to Thin Vegetable Seedlings
Growing vegetables from seed is much less expensive than planting seedlings purchased from a garden center, but there is an extra step when you garden this way. 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, the seedlings are too closely spaced when they sprout. When this happens, you must systematically remove the extra seedlings (called "thinning") to provide enough space for the remaining seedlings to grow to maturity. Thinning seedlings produces healthier plants and higher yields by reducing competition for water and nutrients and providing good air circulation between plants. Fortunately, it is one of the easiest garden tasks.
When to Thin Vegetable Seedlings
Seedlings are usually thinned when they have one to two sets of true leaves. The first leaves, known as the cotelydons, are embryonic seeds stored in the seeds, and the plant is not viable until the next true leaves appear, which will have a much different appearance.
Most plants develop their first true leaves at 2 to 3 inches in height, at which time they are fairly each to grasp by the stem and pull out. If you prefer to pull your seedlings rather than cutting them with scissors, thinning while the soil is still damp after watering will make it easier to slip them out without disturbing other seedligns. And it's best to thinin the evening, which gives the remaining seedlngs a chance to adjust overnight before being exposed to heat and sunlight.
Before Getting Started
Some gardeners find it difficult to sacrifice so many vegetable plants. The good news is that with some plants—like lettuce, beets, chard, and spinach—you can toss the tiny seedlings you remove into salads, stir-fries, or other recipes. These tender greens are delicious.
Thinning long rows of seedlings requires bending and working close to the ground. Thus, a kneeling pad or low bench can helpful for reducing discomfort.
Click Play to Learn How to Thin Vegetable Seedlings
What You'll Need
Equipment / Tools
- Kneeling pad or small bench (optional)
- Garden scissors or snips (optional)
- Flexible rake (optional)
- Yard waste bag
Determine the 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:
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. Toss them in a yard waste bag or compost pile. This method of removing seedlings is easiest to do when the soil is moist and pliable.
Some 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.
If plucking the seedlings has disturbed the soil, you can gently press it back down around the remaining seedlings with your fingers.
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 it 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 to rejuvenate the plants after thinning.
Lettuce. University of Maryland Extension Website