How To Grow Carrots: Soil Preparation, Planting & Harvesting

• Carrots are a cool-season vegetable that grows in spring
• They prefer a very sunny location.
• Carrots need loose soil to grow as long as possible. If planting carrots in a new garden bed with dense clay soil, amend the soil with 1/2 compost before seeding.
• Carrot seeds are very fine and easy to bury too deep. New gardeners should consider pelleted seeds or seeds attached to tape.
• For a summer harvest, plant seeds 2-3 weeks before your last frost. Seeds can be sown again in late summer for a second harvest in fall.
• Thinning seedlings after they appear is very important to ensure that each carrot has enough space to grow.
• Carrots are root vegetables and do not benefit from high-nitrogen fertilizers. A fertilizer with a high “N” number will cause the tops to grow larger at the expense of the roots.
• Carrots can be harvested and eaten at any time after the roots grow a few inches. The longer they grow the sweeter they tend to be.

If you live anywhere in North America with hard clay soil, you may have given up growing carrots in your garden. The tops may have grown beautifully, but the carrots themselves were split, forked, or squashed like a pancake. Don’t take it personally – it wasn’t you, it was the rocky clay soil.

We are so used to seeing multitudes of perfectly formed, long, smooth carrots on grocery shelves and farmer’s markets, that newbie gardeners expect the same results. And if they live where the soil is naturally sandy (known as sandy loam), they’ll have excellent results. But those of us who live atop mountains of clay need to do some work on our soil before planting.

Preparing soil for carrots

The key to growing carrots in soils that aren’t the perfect sandy loam is to work an enormous amount of compost into the garden bed before planting. “Enormous” is a subjective term, so more specifically, at least 30% of the garden soil volume should be finished compost. Soil should also be free of rocks, stones, twigs, and anything else that might get in the way of the carrot root penetrating down into the soil. Carrots need a little TLC, as they don’t have the same capacity to drill down into hard soil as a crop like Daikon radish, which I swear could drill through granite (by the way, daikon radish is superb at breaking up clay soil).

Normally in an organic garden, I don’t advise turning the soil, as it breaks soil structure and disturbs the soil food web. But in the case of carrots grown on land that’s rocky or in clay soil, you’ll have to turn the garden bed, especially in the first season. After a few years, and as other crops are rotated through the same raised garden bed, you may be able to get away with just layering fresh compost on top of the soil. However, I’ve been working my current raised garden beds for 7 years with compost, and still, my clumpy clay wants to put up a fight with my carrots.

Clay soil must be amended with organic material

If your garden is loamy, dark soil, you may be ready to go – broadcast your carrot seeds and enjoy. If however, you have clay soil, you must prepare it and amend it before planting carrots. If not, they may end up as little stubs. In spite of how tough they appear on your table, carrots won’t drive through soil with the force of a vegetable like Daikon Radish.

Across the entire length of your carrot bed, dig down 18″, turning the soil over. Take a look and you’ll probably see that the soil a foot or less below the surface is much denser than the surface soil – that’s where the carrot root hits a wall. Break up the turned soil clumps with your garden spade. Pick through the soil before turning it under again to remove rocks, stones, sticks, twigs, and any other debris. After the first round, turn the soil again, and once again pick out anything that might get in the way of root development. Break the clumps up with your spade.

Add a sufficient amount of finished compost so that roughly 1/3rd of the garden soil volume is compost. Turn the compost in with your spade to achieve a nice mix from the surface to 18″ deep. Rake the bed smooth with a garden rake and once again pick out the small debris that comes to the surface (garden debris is never-ending).

How to plant carrots

Before sowing carrot seed, make sure your garden bed is thoroughly weeded – carrots can’t compete with weeds. Carrot seed is very fine, small seed, which is difficult to sow in proper rows and with proper spacing. There are, however, seeds that are sold attached to tape or pelleted, making it easier to sow in an evenly spaced fashion. (Pelleted seed is seed surrounded by inert materials which dissolve after planting. It’s easier to see when sowing.). Another alternative is to use a hand seed sower set on 1 – my personal preference – which will evenly distribute seeds. If you’re not concerned with an orderly carrot bed, you can also broadcast the seed across the bed and thin the seedlings later.

For a fall garden harvest, plant carrot seeds in the summer, 10-12 weeks before your expected first frost date. For a summer harvest, plant seeds in early spring, 2-3 weeks before your last frost. See more about first and last frost dates.

• Plant carrot seed just below the surface and cover lightly with soil.
• Space the seeds evenly, according to packet directions for your variety – generally speaking, maturing carrots should be about 2.5 – 3 inches apart.
• Gently tamp down the seed bed with your hands after sowing, so the seeds make contact with the soil.
• Water in lightly. 

If you love carrots and are planting a boatload, I highly recommend that you stagger your plantings 2 weeks apart so they don’t all mature at once – you can harvest into late fall if they’re left in the ground.

How to water carrots

The irrigation of carrots is critical. After sowing seeds, and until germination, frequent, low-volume watering is key to keeping the shallow seeds from drying out and a crust forming on the soil. Carrot seedlings are rather delicate and have a hard time pushing through soil crust, and if they dry out, they won’t germinate.

As the carrot tops grow, soil moisture must be maintained to keep the ground soft, so the root can establish and penetrate. Once again, frequent shallow watering is best. As the plants mature, higher volume and less frequent watering are key, keeping around the standard one inch of water per week. I frequently do the “knuckle test” of the garden soil – plunge your finger in up to the middle knuckle – it should feel moist, but not wet.

Drought is especially devastating to carrot seedlings. If rain isn’t falling on the seedlings, be vigilant about irrigating them by hand. Consistent moisture is key, as fluctuations tend to lead to cracked and split roots. Mulching the seed bed with a fine layer of grass clippings is a great way to retain soil moisture.

Thin your carrot seedlings

No matter how careful you are about spacing your seeds, carrot seeds find all kinds of ways to group together, especially if you have heavy rains pre-germination. As soon as seeds germinate, start thinning the seedlings to the appropriate spacing for the variety. Carrots that are crowded not only end up being puny but also malformed, as they fight for space. Thin when the tops are 3″ and again at 6″, and as necessary as the plants mature.

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Fertilizing carrots

According to Leonard Perry, Horticulture Professor at the University of Vermont, “Don’t use fresh manure or excess nitrogen on carrots.  This can cause roots to be forked, split, and rough or hairy.  I like to work in an organic vegetable fertilizer prior to planting.  Carrots prefer moderate levels of nitrogen, and low levels of phosphorus and potassium.“

Compost can usually provide all of the necessary fertilization needed. Occasional feedings with fish emulsion seem to make them thrive (but that’s just an anecdotal observation).

When to harvest carrots

The really cool thing about carrots is that you can eat them as soon as the roots have grown a few inches.  And they get better as the season continues.

As fall arrives, your carrots will start to mature. I leave my carrots in the ground and harvest only as I need them, until very cold weather is imminent. To insulate them against freezing temps, I add straw or compost on top of the soil.

As growth slows to a crawl with cooler temps, the carrots become sweeter as sugar collects in the root. As long as you harvest before the ground freezes, your carrots will be just fine. It’s not unusual for me to be digging in the bed at Thanksgiving to serve fresh carrots for our family gathering. Then shortly after the holiday, I harvest what’s left, put a few dozen in the refrigerator, and slice, blanche, and freeze the rest in mason jars for soups and stews over the winter.

We garden in Pennsylvania, United States, zone 6B. Much of the info we share is based on gardening in our temperate area. But many of the flowers, vegetables, and fruit we write about can be grown in soil other than ours (clay) and significantly different weather conditions and elevations. You might need to choose specific varieties for your region, modify your garden, add soil amendments, or adjust the soil pH to match our results. Please check your local university extension website for specifics for your area.