Thinning carrots is a necessary task to ensure a good crop of long, carrot roots.

Thinning carrots: How to plant and thin carrot seedlings

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Thinning carrots is one of those tedious garden tasks that, although necessary, isn’t much fun. But why do we need to thin carrots anyway? It’s because carrot seeds are very small and it’s easy to accidentally plant them too thickly when sowing the tiny seeds. If carrots are spaced too close together, there isn’t enough room to develop large healthy roots and they may become stunted or misshapen.

Learn how to thin carrots for the highest quality crop.

Carrots can be planted every few weeks from mid-spring to mid-summer to ensure a long season of super-sweet homegrown roots

How to plant carrots

Carrots grow best in a sunny site with deep, well-draining, clump-free soil. Of course not all of us have perfect soil, myself included, so I grow most of my vegetables in raised beds. If your soil is shallow or heavy, stick to compact varieties of carrots like Red Cored Chantenay, which has short, thick roots that only grow about five-inches long. Or, baby varieties like Little Finger that have slender four-inch long roots. And while I generally grow at least a handful of varieties like Ya-ya, Napoli, Atomic Red, and Imperator, I also love the many different rainbow blends of carrots, like Carnival Blend that offer a bold mixture of orange, purple, red, yellow, and white varieties.

Once you have seeds in hand and have picked a good site for your carrot crop, it’s time to amend the soil. I loosen the top foot of soil in my beds using a garden fork, working in around an inch of compost. If using manure, be sure it’s aged at least two years as the higher nitrogen levels of half-composted manure can cause carrot roots to fork or become densely covered in root hairs. 

Thinning carrots should be done in early summer.

Thinning carrots makes sure the roots have ample space to grow.

Direct sow carrot seed in the garden in mid-spring, about a week or two before the last expected spring frost. If you have a cold frame or polytunnel you can plant up to two months earlier. To seed carrots, make a shallow furrow in the bed, about one-quarter to one-half deep. I usually make the furrow with a finger or lay the handle of my garden fork on the soil surface and press gently.

This is your first opportunity to minimize the need to thin the carrot bed later on. How? By sowing just two to three seeds per inch and spacing them as best as you can. Cover the seeds with a thin layer of soil or horticultural vermiculite and irrigate the bed thoroughly with a gentle spray of water. You’ll need to keep the soil consistently moisture while the seeds are germinating, which can take 14 to 21 days, sometimes longer.

For the longest season of high-quality carrots, succession plant every four to six weeks from mid-spring to mid-summer. My final carrot sowing is in late July and these are the carrots we harvest all autumn and winter from our cold frames, mulched beds, and polytunnel.

Plant pelleted carrot seeds

One of the easiest ways to space carrot seed correctly and reduce thinning is to plant pelleted seeds. Pelleted seeds are coated with an inert clay which makes all the seeds the same size and shape. This is convenient for market gardeners and farmers who use seed sowing equipment, but it’s also great for gardeners who will find the larger seeds easier to handle and plant. Space pelleted seeds an inch apart. Provide adequate moisture until seeds germinate and are growing well.

The downside to using pelleted seeds is that most seed companies only offer a few varieties of pelleted carrot seeds so you’re limited in the varieties you can grow.

Plant pelleted carrot seeds to reduce thinning

Reduce the need to thin carrots by planting pelleted carrot seeds. Pelleted seeds (on the right) are coated in inert clay and their large, uniform size makes sowing the seeds much easier.

Thinning carrots: how to thin carrot seedlings

For me, thinning carrots begins when the seedlings are about three to four inches tall. I start by gently pulling out weak or stunted-looking seedlings and once they’ve been removed, it’s time to thin the rest of the bed. At this stage, I try to thin the plants to about an inch apart, which usually means removing every second seedling. If I didn’t use pelleted seeds, there may be a few random clumps of plants that are in desperate need of thinning. Heavy rains can also cause seeds to wash and pool on the soil surface and come up in clumps.

When thinning carrots, carefully pull the tiny seedlings from the soil or pinch off the foliage at soil level. When you’re done, gather up the discarded seedlings and bury them in your compost pile. The smell of fresh carrots can attract carrot rust flies. You can also gently mound up some soil around the tops of your carrot plants at this time to help keep the roots covered. If the roots are exposed to light as they grow, their shoulders will turn green and bitter.

After the initial thinning, I follow up around a month later with a second thinning session. Every second carrot is again removed, leaving the roots spaced about one and a half to two inches apart. The good thing about this second thinning is that you’re rewarded for your work with baby carrots! Yum!

Learn how and when to thin carrot seedlings.

Follow up your first carrot thinning with a second session a month later. This second thinning will result in sweet baby roots.

Can you transplant some of your carrot thinnings?

The quick answer is yes. The longer answer is that while you can transplant carrot seedlings, you raise the risk of ending up with twisted or misshaped roots. If you plan on re-planting some of your carrot thinnings, be sure the root of each seedling is planted as straight as possible in the new spot. Water well after re-planting.

Watch this video to learn about why carrots sometimes don’t grow straight and what to do to fix it.

For more information on growing great vegetables year-round in your food garden, check out my best-selling book, The Year-Round Vegetable Gardener. And you’ll find more food-growing tips in these articles:

Learn how and when to thin carrots.

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