Why Are My Radishes Splitting? (Plus Secrets To Stop It)


If you grow radishes in your garden, you know how disappointing it can be to dig up split radishes.  I was wondering what causes this problem, and how to prevent it.  Here’s what I found out.

So, why are your radishes splitting?  Radishes will split if they encounter a lack of water followed by too much water (also called uneven watering).  Radishes will also split if they are left in the ground too long.  In addition, over fertilizing with nitrogen or potassium can cause radishes to split.  A boron deficiency can also cause cracking in radishes.  Finally, cold nighttime temperatures can cause radishes to split after they are harvested.

Fortunately, there are ways to alleviate all of these problems, but they will require some work on the front end.  Let’s take a closer look at why your radishes are splitting, and how to prevent each of the possible causes.

Why Are My Radishes Splitting?

There are many reasons that can cause your radishes to split, but one of the most likely causes is uneven watering: a lack of water, followed by too much water.  Let’s dig deeper into this problem and some possible solutions.

Radishes Splitting Due To Uneven Watering

Uneven watering is a common cause of radishes splitting.  Watering is difficult to get right in the summer, since you can have hot, dry heat one day and a thunderstorm the next.

dry soil
Dry soil can be a big problem if you want to avoid splitting radishes.

To ensure even watering, first check the weather forecast in your area.  This will help you to avoid watering too much before a big storm dumps an inch or more of water on your garden.

Also, be sure to check the moisture levels in your soil frequently.  The best way to do this is to use your fingers to feel the soil at a depth of 2 or 3 inches below the surface.

If the soil is damp, you can leave it alone for a while.  If it is starting to get dry, it is time to water!

During hot, dry, and windy weather, water will evaporate from the soil quickly.   You may need to check the soil a couple of times a day during these times.

If you find that your soil is consistently dry or that you can’t keep up with watering, try putting down a layer of mulch or compost over the soil around your radishes.  Mulch can help to retain moisture in the soil, and will eventually break down to provide nutrients and organic material for your plants.

For more information, check out my article on how to treat dry soil.

On the other hand, if you over water in response to a dry day or two, then you can cause your radishes to split.  There are two types of over watering: too much water in a short time period immediately following a dry spell, and watering too often, which can lead to root rot.

radishes
Uneven watering can cause your radishes to crack, so keep an eye on the weather forecast, check the soil frequently, and water carefully!

Use a handheld hose instead of a sprinkler to control the amount of water your plants get.  Even better, you can use a drip irrigation system to slowly water your radishes.

watering can
Watering by hand with a garden hose or watering can lets you control the amount of water each plant gets.

For more information, check out my article on over watering your plants.

You can also check out this article from the Utah State University Extension.

One last thing to remember: compacted soil may not allow the taproot of a radish to get enough water, which can also lead to uneven moisture levels and splitting.  To prevent this, avoid stepping on your soil before or while planting seeds or transplanting seedlings.

If your soil is too compacted, you might consider rototilling to loosen it up a bit.  For more information, check out my article on the cost of rototilling.

Radishes Splitting Due To Being In The Ground Too Long

Another possible cause of splitting radishes is leaving them unharvested in the ground for too long.  The longer a radish is in the ground, the longer it may be exposed to uneven watering or cold nighttime temperatures, both of which can cause splitting.

The time to maturity for radishes varies quite a bit, from less than a month (25 days) to over two months (70 days or more).  Be sure to read the packaging carefully and make a note of the time to maturity of the radishes you bought.

Also make a note of the time you planted the seeds, and add that many days to determine when you should expect a harvest.

For example, let’s say that you bought radish seeds that take 40 days to maturity, and you plant the seeds on April 1.  There are 30 days in April, so you would expect the plants to mature 10 days into May, on May 10th or so.

As this date approaches, you should check daily to see if the radishes are ready for harvest.  Some may mature faster than the package states, and the ideal window for harvesting is only a few days wide.

growing radishes
As your radishes get closer to maturity, check on them every day to see if they are ready to harvest.

Radishes Splitting Due To Over Fertilizing

Over fertilizing is another possible problem that can cause radishes to split.  Nitrogen and potassium are two likely culprits when radishes split due to over fertilizing.

According to Michigan State University, “Excessive N and K appear to make radishes brittle and may cause cracking under some circumstances … Potassium salts are very soluble and may be the main factor in cracking. If cracking is a problem, reduce potash applications.”

Note that N stands for nitrogen, and K stands for potassium, as in the NPK ratio on a bag of fertilizer.  For more information, check out this article from the Michigan State University Extension on recommendations for growing radishes.

Remember that over fertilizing can cause other problems, such as burning your plants or even killing them.

For more information, check out my article on over fertilizing your plants.

Many conventional fertilizers are balanced, meaning that they contain nitrogen and potassium (in addition to phosphorus and possibly other nutrients).  Luckily, there are fertilizers that are low in nitrogen, potassium, or both that you can use instead of balanced fertilizers.

For more information, check out my article on low-nitrogen fertilizers.

Also, keep in mind that manure can be good for your garden, but you should not apply it fresh!  Let it compost first, or else you may burn your plants.  For more information, check out my article on where to get manure.

manure
Using too much fresh manure directly on your plants can cause too much nitrogen, which can cause radishes to split.

My recommendation is to try using compost before moving to fertilizer from a bag.  Compost provides both nutrients and organic material to your soil.  Best of all, it can be made from yard and kitchen waste you may already have!

For more information, check out my article on how to make your own compost.

Radishes Splitting Due To Boron Deficiency

A boron deficiency is another reason that radishes may split.  According to Michigan State University, “In radishes and turnips, boron deficiency causes cracking and poor root development.”

Before you add anything to your soil, you should make sure that your soil really does have a boron deficiency.  The best way to tell for sure is to do a soil test.

To do this, you can send a soil sample to your local agricultural extension office.  If you tell them what you are growing, they will send back recommendations with the test results.

For more information, check out my article on how to do a soil test.

Radishes Splitting Due To Cold Nighttime Temperatures

Cold nighttime temperatures are another reason that your radishes are splitting.  If you planted late and have a short growing season, then cold weather in the early fall could be the culprit for cracked radishes.

According to Michigan State University, “Cracking during harvest is a problem in the fall when night temperature falls below 45°F. The radishes come out of the ground whole, but crack when dropped or handled … During the fall, harvest after 10:00 a.m. This will allow the roots to warm up slightly and translocate some water to the leaves. Cultivars that are very susceptible to cracking should not be grown for fall harvest.”

Another way to avoid this problem is to plant radishes early or start your radish seeds indoors.  That way, you can transplant them outside later in the spring to avoid frost.

You can even grow your seedlings indoors in cardboard boxes, and then bury the boxes directly in the soil in your garden.  For more information, check out my article on growing plants in cardboard boxes.

Can You Eat Split Radishes?

Yes, you can eat split radishes, as long as you clean them properly.  If there is dirt inside the crack, wash it out the best you can.

If dirt remains in the crack, use a knife to cut away the dirty part of the radish.  Then, cut up the rest of the radish and cook it (boil, steam, or sauté in oil) to get rid of any bacteria.

white radishes
If any of your radishes are split, try to wash out the crack, or cut away the dirty parts before cooking and eating.

If you want to avoid split radishes and dirt in the cracks, I found an interesting Asian heirloom radish variety for you to try.  For a unique twist on radishes, try Dragon’s Tail Radish from Burpee.

This radish is harvested not for the root, but for the long, thin, purple seed pods that grow above ground.

Conclusion

By now, you have a much better idea of what can cause the radishes in your garden to split open.  You also have some ideas on how you can take action to prevent the most common causes of this problem.

I hope you found this article helpful – if so, please share it with someone else who can use the information.  If you have any questions or advice about radishes, please leave a comment below.

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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