Why Are My Radishes Long and Thin? (Secrets To Stop It)

It is disappointing for any gardener to put in the care and hard work to grow radishes, only to find that the roots are long and thin at harvest time.  However, there are specific reasons that radishes grow this way, and luckily, there are also ways you can stop it from happening.

So, why are your radishes long and thin?  Radishes will grow long and thin in response to hot weather, unsuitable soil, and competition with other plants.  Too much nitrogen in the soil may also cause radishes to grow long and thin.

Let’s take a closer look at why radishes grow long and thin under these conditions.  Then, we’ll look at some ways to prevent these problems and save your harvest.

Let’s get started.

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Why Are Your Radishes Long and Thin?

There are several possible reasons that your radishes are long and thin.  Let’s start with temperature, one of the more common causes.

Radishes Bolting Due to Hot Weather

Radishes are known as a cool-weather crop.  According to Clemson University, the optimal temperature for growing radishes is 50 to 65 degrees Fahrenheit (10 to 18.3 degrees Celsius).

When temperatures are much warmer than this, your radish plants may bolt.

What Is Radish Bolting?

When a radish bolts, it is switching from vegetative growth (of leaves and roots) to reproductive growth (of flowers and seeds).  This will occur naturally with age, but the process will speed up when temperatures are warm.

When temperatures are too warm, radishes are more likely to bolt, producing flowers and seeds, at the expense of their roots.

When a radish plant bolts, it sends up a flower shoot, which eventually produces seeds.  This is the method by which the plant reproduces.

Unfortunately, when a radish plant sends up the flower shoot and produces seeds, this takes energy away from the growth of leaves.  It also causes the root to become bitter, since nutrients and energy are put into the flowers and seeds instead of the roots.

Note that radish may also bolt in response to a change in the length of the day (natural passing of time).  When a radish plant knows that the days are getting shorter and cold is approaching, it may bolt to produce seeds before it dies.

Likewise, bolting may also occur in radish plants due to a lack of water or nutrients.  For example, if the plant does not think it can survive a drought, then it may bolt quickly in an attempt to produce flowers and seeds before it dies.

For more information, check out this article on bolting from Wikipedia.

Overcrowding & Competition Makes Radishes Long and Thin

Another reason that radishes will grow long and thin is due to competition with other plants (including nearby radishes!)  When there are too many plants in one area, they will compete with one another for nutrients and water.

In addition, when radishes are planted too close together, the roots physically have nowhere to go.  Since they cannot grow wider, they instead grow longer, going deeper into the soil in search of nutrients and water.

Your Soil Is Unsuitable For Growing Radishes

Radishes, like carrots, prefer to grow in loose, sandy soil.  This means that the soil should be smooth, with no rocks, roots, or dirt clumps.

rocky soil
Lots of rocks in your soil can prevent radishes from growing as wide as they could with loose, rock-free soil.

Any such obstructions will prevent the radishes from growing properly and keep them from getting as wide as they should be.

Your Radishes Are Long and Thin Due to Nutrient Imbalances

According to the Iowa State University Extension, too much nitrogen can encourage radishes (and other plants) to focus on green growth (leaves above ground) instead of root growth (the part of the radish we want to grow and eat).

It is possible to over fertilize your plants, so check out my article on over fertilizing and my article on low-nitrogen fertilizers.

Your Radishes Are Long and Thin Due To Lack of Sunlight

If your radishes are planted in an area with too much shade, it is possible that they won’t be able to produce large, fat roots due to the lack of sunlight.

sunlight through forest
Don’t plant radishes too close to trees or other tall crops, since they need sunlight to grow properly.

This can happen if nearby trees or other tall garden crops are growing lush foliage, which will block sunlight from the radish plants.

It can also happen if your radishes are planted too close to a structure such as your house, garage, barn, or shed.

How to Make Radishes Grow Bigger

Now that we know whey radishes grow long and thin, it’s time to combat the problem.  Let’s dive into some of the ways to make your radishes grow bigger.

As is often the case with gardening, a good place to start is by looking at the soil.

Smooth out Your Soil

Your radishes will grow better when the soil is loose and full of nutrients.  If your soil is heavy clay, then adding some compost is a good way to loosen it up a bit.

For more information, check out my article on compost.

Another way to make your soil better for growing radishes is to remove the rocks.  For more information, check out my article on how to remove rocks from soil.

You can also consider tilling the soil to loosen it up and break up dirt clumps.  You can do this with a shovel, or use a rototiller.  For more information, check out my article on the cost of rototilling.

A rototiller is one way to loosen up soil.

You might even consider adding sand to your soil, in order to provide a loose growing medium for your radishes.  The less resistance they encounter in the soil, the easier it will be for them to grow wider and longer (deeper).

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Plant Heat-Resistant Radish Varieties

If your radishes are long and thin due to bolting, one remedy is to plant heat-resistant radish varieties in your garden.  These radishes will resist bolting in hot weather, giving your crop more time to grow bigger, wider roots before the plant starts to produce flowers and seeds.

I have included a table below that shows various heat-tolerant radish varieties, along with their time to maturity, color, and type.

Days to

All of these radish types (and more) are available from Johnny’s Selected Seeds.

Thin Your Radishes after Planting

One major cause of long and thin radishes is overcrowding and competition between radishes.  This will occur if you forget to thin seedlings after they emerge.

Thinning seedlings means that you kill off some of the seedlings in order to give the remaining ones a chance to grow bigger.

radish seedlings
Radish seedlings should be thinned so that the remaining seedlings are 2 to 4 inches apart, depending on the variety (larger radishes need more space to grow). Check the seed packet to make sure!

Generally, you should thin radishes so that they are 2 inches apart.  However, some larger varieties may need more space (up to 4 inches for some varieties).  To find the exact spacing, check the seed packet or website where you bought the seeds.

In addition to thinning your seedlings to prevent competition, you also need to be vigilant about weeding.  Weeds will compete with radishes for nutrients and water in the soil, just as radishes too close together will compete with each other.

For more information, check out my article on thinning seedlings.

Reduce Heat to Prevent Radishes from Bolting

As mentioned earlier, heat is a major cause of radishes bolting, which can lead to long and thin roots as the plant puts its energy into producing flowers and seeds.  Here are a few ways to keep your radishes a bit cooler and delay bolting for a time.

Provide Shade to Your Radishes

Providing shade for your radish is very important to avoid bolting, especially in the hottest weeks of the summer.  The temperature in the shade can be several degrees cooler than the temperature in the sun.  This can make all the difference in whether a radish plant bolts or not.

One way to provide shade for your radishes is to plant them near other taller plants.  Since most plants are taller than radish, you have lots of options!

Vining plants that climb stakes or trellises, such as tomatoes and cucumbers, are great shade-providing neighbors for radishes.  You can plant radish close to them to provide shade during part of the day, while still giving the radishes enough light to grow.

arbors on path
If you have an arbor, you can use it to provide shade to radishes when temperatures are too high and would cause your plants to bolt.

If you use an A-frame trellis, arbor, or pergola to support climbing plants (such as tomatoes, cucumbers, squash, or grapes), then you can plant radishes underneath the structure.  That way, the structure itself and the leaves of the taller vining plants will provide shade to the radishes.

For more information, check out my article on trellises, arbors, and pergolas.

Another option is to use shade cloth or floating row covers to keep some of the sunlight (and thus the heat) from getting to your radishes.  Row covers are basically a fabric material that filters out sunlight (you can choose from different materials that allow more or less light through).

Finally, when planning for next year’s garden, scout out an area for planting radishes that has a bit of natural shade during the hottest part of the day.

Use Mulch to Insulate Your Soil against Heat

Another way to keep your radishes a bit cooler is to insulate the soil they are growing in.  To do this, use some type of mulch to cover the surface of the soil.

In addition to preventing weeds, mulch will help the soil to retain water and prevent the soil from getting so hot.

wood chip mulch
Mulch helps to retain water and keep the soil cool, which will delay bolting in radishes.

Wood chips are often used as mulch, but don’t forget that you can use many different materials as mulch to cover your soil, including:

  • Hay
  • Straw
  • Grass clippings
  • Leaves (whole or chopped up by a lawnmower)
  • Cardboard boxes (flattened)
  • Compost

Be careful about using manure as mulch – it should be fully decomposed before applying it to your garden.  Otherwise, you might burn your plants due to high salt content.

Keep Your Radishes Watered

It takes energy to evaporate water.  This is the way that your body cools off on a hot day: you sweat, and when the water in the sweat evaporates, it cools you off.

The same principle applies to gardening.  If you keep the soil around your radishes watered, it will stay slightly cooler than the surrounding soil due to evaporation.

garden hose
Keep your radishes watered to keep them a bit cooler and reduce moisture stress on hot dry days.

Also, keeping your soil moist will prevent water stress on your plants.  Water stress is another reason that radishes sometimes bolt and becomes bitter, so make sure to keep an eye on the soil moisture and on the radish itself.

If the radish leaves look wilted, check the soil with your fingers.  If it is dry down to a few inches, make sure to give the plant a thorough watering to help the radish perk back up and stay cool.

For more information on watering, check out this article on radishes from the University of Minnesota Extension.


By now, you have a much better idea of why your radishes are long and thin, and also why it happens.  You also know what you can do to keep radishes a bit cooler and prevent bolting, bitter flavor, and long thin roots.

I hope you found this article helpful – if so, please share it with someone who can use the information.

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Jon M

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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