When I was first introduced to daikon radishes, I was so amazed by their size that I had to try growing them myself. But much to my disappointment, my daikons didn’t get anywhere as large as I was expecting them to get. Turns out, there were a couple of mistakes I was making.
Daikon radishes may grow small if they’re planted too close together, are not getting enough sunlight, or the temperature is too hot. If you’re growing in raised beds, your beds may not be deep enough for these long radishes to reach their full length.
This guide will help you to not make the same mistakes I did as I’ll share the tips and tricks that I’ve now learned for growing big, beautiful daikon radishes.
Why your daikon radishes aren’t getting big
These are the common mistakes that most gardeners make when growing daikon radishes that can significantly stunt the plant’s growth. Luckily, there’s a solution to all of them.
Daikons planted too close together
Like most plants, daikon radishes don’t like to compete with other plants for space. These radishes can grow to be about 2 feet long and their green leaves can spread out as far as 3 feet in any direction.
Plant your radishes about an inch apart and then thin them out as they grow. By the time they reach full maturity, they should be about 4 to 5 inches apart.
Daikons not getting enough sunlight
Radishes are generally a low-maintenance crop and can often feel like one of those things that you can just plant and forget about until it’s time to harvest. That’s what I thought anyway.
If your daikon radishes aren’t getting enough sun, then their roots will not get that big and they’ll focus their energy on producing bigger leaves. Make sure that the area where you plant your daikons gets at least 6 hours of sunlight per day.
The outside temperature is too warm
Radishes are in the brassica family with other common veggies like broccoli, cauliflower, kale, and cabbage. These are also known as cool-season crops. As you can probably guess by the name, cool-season crops don’t do well in warmer temperatures.
When radishes are exposed to several days of hot weather (temperatures consistently over 85 degrees) they will start to bolt before reaching their full size. Once a radish bolts, its flavor quality is severely diminished and can become quite bitter.
For those in temperate climate zones, the best time to grow daikons is in the spring or fall season. This way you’re avoiding the summer heat.
Raised beds are not deep enough
If you’re growing daikons in any kind of raised bed, it’s important to make sure that the bed is deep enough.
As I mentioned before, daikons can be up to 2 feet in length. If you’re having a hard time picturing that, imagine a radish that’s the length of your forearm from fingertip to elbow. Sometimes they can be even longer!
If your raised bed is too short vertically, the radish has nowhere to go. Sometimes they can continue to grow into the ground below your raised beds but only if the soil is not too compacted.
Similarly, if you placed a piece of fabric in the bottom of your raised bed before filling it with soil, the daikons will have a difficult time growing through this fabric.
How to grow big daikon radishes
Planting your daikon radishes far enough apart, in well-lit areas, and in raised beds that are deep enough for the roots to grow will certainly set your daikon radishes up for success. But here are some other good things you can do to maximize daikon radish growth.
Soil and water preferences
Daikon radishes prefer loose loamy soil with a slightly acidic pH between 6 and 6.5. If your soil is slightly compacted, have no fear. Daikon radishes are actually fantastic at growing through pretty rough soil.
Unless your soil is virtually impenetrable with a dibbler, your daikons should have no problem breaking through the soil. Don’t have a dibbler? Check out this article to help you figure out the best dibbler for your garden.
Daikon radishes also prefer consistently moist soil. Depending on your climate zone, you’ll probably have to water your radishes about every other day. If your region stays pretty wet, be careful not to over water or your radishes may split and rot. You can check your soil humidity using a rain gauge.
Direct seed daikon radishes
The best way to get good germination in your daikon radishes is to plant the seeds directly into the ground instead of starting them indoors and transplanting them later.
Radish seedlings are very tender and can be very difficult to transplant leaving you with damaged roots and poor plant growth.
But with direct seeding, thinning your radish seedlings becomes very important as I mentioned earlier. It’s a bit tedious to try and get perfect spacing with such small seeds so it’s okay if your seeds are planted close together and you thin them out as they grow.
If you have the space in your garden for it, I would highly recommend succession planting. Daikon radishes are those “one-and-done” types of plants meaning that once they’re harvested, they won’t produce anymore unless you plant more seeds.
This is where succession planting comes in handy. If you plant new daikon seeds every two weeks then you will have new radishes to harvest every two weeks once they reach full maturity.
This is helpful because you won’t be bombarded with a ton of huge daikons all at once since their harvesting will be staggered. It can also extend your season so that you have a continuous radish harvest for several weeks.
When are daikon radishes ready for harvest?
You can expect your daikon radishes to reach full maturity in about 40 to 70 days from when the seeds were planted.
Similar to carrots, the top of daikons will start to stick out of the ground as they get closer to their harvest date. They should have nice full leaves on the top that are between 7-12 inches in length. The leaves are also edible by the way!
It can be hard to tell when root crops are ready for harvest because we can’t see what they look like underground. Whenever I’m unsure, I pull a test one just to check on its progress.
Daikon radishes should be at least 8 inches in length when they’re ready but oftentimes they’re much bigger than that.
Hopefully, you’ve found this information helpful and are looking forward to growing tons of huge daikons this year. As long as you space them far enough apart, give them plenty of sunlight, and make sure your beds are deep enough for them to spread their roots, you’ll have the biggest and most beautiful daikon radishes you’ve ever seen.