How Much Depth and Space Do Carrots Need to Grow?


When growing carrots, it is important to give them the space they need to thrive.  Otherwise, you will end up with carrots that are small and deformed – despite all your hard work during the growing season.

So, how much depth and space do carrots need to grow?  The roots of carrots can grow as long as 12 inches (30 centimeters), so the soil for growing carrots should be at least 12 inches deep.  Carrot seeds should be planted 1 inch (2.5 centimeters) apart, and later thinned to 3 inches apart to allow each root enough space to grow.

Of course, some carrot varieties are shorter than 12 inches, but are much fatter than other carrots.  These carrots will need less depth and more space between plants.  Let’s take a closer look at how much depth and space carrots need to grow.

How Much Depth and Space Do Carrots Need to Grow?

Carrots will need smooth soil at a depth of up to 12 inches (30 centimeters) to grow properly.  Carrot roots (the part of the plant you eat!) will grow between 2 and 12 inches (5 and 30 centimeters) long.

carrots
Some carrot roots can grow up to 12 inches long (not counting the greens that grow above ground!)

Since the entire root of a carrot grows underground, you will need soil that is at least a foot deep.  To give yourself a little margin of error for taller varieties (such as Burpee’s A1 Hybrid Carrot), you might want to loosen the soil to a depth of 16 inches (40 centimeters) or so.

Of course, if you want to set a record, you will need much deeper soil than that.  That’s because the world’s record for the longest carrot is over 19 feet (6.2 meters)!

A carrot will need 3 inches (7.6 centimeters) of space around it to grow, since most carrots will be 0.5 to 1.5 inches (1.3 to 3.8 centimeters) wide at harvest.

In any case, carrots will need smooth, sandy soil in order to grow their best.  To find out more about the ideal soil for growing carrots, read my article here.

The soil you use to grow carrots should always be free from rocks, roots, hard dirt clumps, and other obstructions that might cause carrots to grow deformed.  You can use a soil sifter to remove this debris from your soil. 

The depth of a raised bed (planter box) or grow bag will need to be a little taller than 1 foot.  This will leave space to hold all of the soil you need for growing carrots, plus some extra space at the top.

How Deep Should a Raised Bed (or Planter Box or Container) Be For Carrots?

I recommend a depth of 18 inches (46 centimeters) for a raised bed, planter box, or container to grow carrots.  Here’s a breakdown of the depth:

  • Bottom 15 inches: this includes space for enough soil to contain carrots that can grow up to 12 inches long.  This gives you a 3-inch margin for error, just in case your carrots do really well and grow a little longer than expected!  It also gives you a little space for planting the carrot seeds at the proper depth (only 0.25 inches, or 0.6 centimeters).
  • Top 3 inches: this includes space for extra material later in the season.  For example, you might want to work some fertilizer into the soil, or add a thin layer of mulch on top of the soil to retain water and insulate the soil.  This extra space will also prevent you from accidentally spilling soil out of the raised bed.  If the soil was filled to the very top of the container, it would be too easy for it to escape due to heavy rain or strong winds.

If ergonomics or personal preference demands more height for your raised bed, then you could also build it on top of a mound of soil.  You might even use legs to raise up the entire bed even further to suit your needs. I know that knees are often the first to go as you get older – I can already feel it!

raised bed
A raised bed should be at least 18 inches tall to allow enough depth for growing carrots.

For every 1 foot (12 inches or 30 centimeters) of length in your raised bed, you should be able to plant 4 carrots in a row (3 inches between plants).  So, you should be able to plant 16 carrots in a row inside of a 4 foot long raised bed.

If the width of your raised bed is 2 feet, then you can plant 8 rows of carrots.  This would give you a total of 128 carrots in a 4 foot long by 2 foot wide raised bed.

To find out how many carrots you can fit in your raised bed:

  • Multiply the length of the raised bed (in feet) by the width of the raised bed (in feet).  Then, multiply that result by 16.  (Note: this assumes a space of 3 inches between carrots).

What Size Grow Bag for Carrots?

I recommend a depth of 16 inches (41 centimeters) for a grow bag to grow carrots.  Please see the previous section for a breakdown of the depth.

Note that 16 inches still leaves a little space at the top of the grow bag.  For a grow bag with a diameter of 20 inches (51 centimeters), you should expect to fit about 35 carrots.

To find out how many carrots you can fit in your grow bag:

  • Take the diameter of the grow bag (in inches) and multiply it by itself.  Then, multiply that result by 0.087.  (Note: this assumes a space of 3 inches between carrots).

If you are looking for grow bags, you can check out the many different sizes available on the Vivosun website.  They have 1, 2, 3, and 5 gallon grow bags, with various sizes all the way up to 30 gallons.

Note that the 20, 25, and 30 gallon sizes all have a height of 16 inches (41 centimeters), as recommended above.  The diameters of these grow bags are 20, 22, and 24 inches, respectively, which would allow space for growing 35, 42, and 50 carrots, respectively.

Vivosun Grow Bag Dimensions

Volume
(gallons)
Diameter
(inches)
Number
Of
Carrots
202035
252242
302450

How Much Space between Carrot Seeds? (Planting Carrot Seeds)

When you first plant carrots, you should leave about 1 inch (2.5 centimeters) of space between the seeds.  Cover the carrot seeds with a thin layer of soil that is 0.25 inches (0.6 centimeters) thick.

seed package
Leave an inch between carrot seeds when planting – you can thin the plants later in the season.

Always sow your carrot seeds directly into the garden.  The roots of young carrots are too sensitive to be transplanted, so the seeds cannot be started indoors (that’s ok though – carrots are a cool-weather crop, and they don’t mind chilly temperatures if you start them outside early, about 3 weeks before the last frost in your area).

Wait until your carrot seeds germinate and grow before thinning them.

How Much Space between Carrot Plants? (Thinning Carrot Plants)

After your carrots have been growing for a while, it will be time to thin them out.  It seems cruel, but it will help to ensure that the healthy ones that remain will grow as large as possible.

According to the University of Minnesota, you should wait until the larger carrot seedlings are 3-4 inches (7.5 to 10 centimeters) tall before thinning.  (Note that the height refers to the greens of the carrots that grow above the soil surface.)

At this point, thin the carrots to 3 inches apart by pulling up the smaller ones.  You may be able to get away with 2 inches between carrots, but the spacing could be tight.

If you don’t use proper thinning leave enough space between carrot plants, you might end up with smaller carrots as a result of competition due to crowding.

As your carrots continue to grow, be sure to provide enough water to keep the soil moist.  Remember that carrot roots can grow up to 12 inches deep!

You will need to water more often in sandy soil (which drains well).  You will also need to water more often when it is sunny and temperatures are warmer (due to faster evaporation).

What Happens if You Plant Carrots Too Close Together?

If you plant your carrots too close together, you may end up with small or deformed carrots.  Small carrots are the result of competition between neighboring plants for water and nutrients in the soil.

Deformed carrots can occur when the roots of two carrots “bump into” each other underground and become tangled together.  This is much more likely if you fail to thin your carrots enough.  It will also happen if you forget to remove rocks and other debris from the soil.

deformed carrot
Carrots can grow deformed if they encounter obstructions in the soil, such as rocks, roots, or hard soil clumps.

Also remember that other plants (including weeds) can compete with carrots for water and nutrients.  Taller plants, such as tomatoes, beans, and corn can easily shade carrots and block out their sunlight.  For this reason, you should pull weeds carefully and avoid planting carrots too close to other tall crops.

How Much Space between Rows of Carrots?

When planting in your garden, you should leave 18 inches (46 centimeters) between rows of carrots.  This leaves enough space to walk between rows so that you can pull weeds and water, fertilize, inspect, or harvest your carrots.

When planting in a raised bed or grow bag, you do not need to leave so much space between rows.  This is because you will not be walking on the soil in your raised bed or grow bag!

As long as the raised bed is not too wide, you should be able to reach all of the plants from outside of the raised bed.  In this case, you can simply leave 3 inches (7.5 centimeters) between rows of carrots in your raised bed.

Conclusion

Now you know exactly how much depth and spacing carrots need to grow their best.  You also know how deep to plant the seeds, and how to thin them to allow the strongest seedlings to continue growing.

I hope you found this article helpful – if so, please share it with someone who will find the information useful.  Now it’s time to get back out in the garden and make your carrots grow!

jonathon.david.madore

Hi, I'm Jonathon. I’m the gardening guy (not guru!) who is encouraging everyone to spend more time in the garden. I try to help solve common gardening problems so that you can get the best harvest every year!

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