This week we will be talking about radishes. August is a good time to start planting radishes for a fall harvest, so I want to talk about how you might want to think about planning for and planting your fall radishes and also about some varieties that have actually been bred specifically for fall production.

Many people think of radish as a spring crop because, well, they are! It’s less well known that radishes are a great late-summer and early fall crop and that some varieties actually require the cooler, shorter days of fall to bulb up.

Frankly, I learned this the hard way. Years ago I got REALLY into radishes and started ordering all these new varieties of daikon and watermelon radishes to try out. I sowed them in the spring and early summer, when I would normally plant radishes and every time they would germinate, and grow up until the point that I would think they were ready to harvest and I would go to pick them and they would be all greens and no root. So I would leave them a little longer and they would start to bolt, but still no root.

I decided to dig deeper and it turns out that radishes can be split into three categories, when it comes to seasonal preference, there are spring, summer and fall radishes. The lines between spring and summer radishes are a little blurred, but the more you know about their preferred growing conditions, the more successful you’ll be in the long run. Generally, the radishes denoted as “spring” types can often be planted throughout the entire growing season. The designation of spring radish can be a little confusing, so it’s probably easiest to just remember that spring radishes are the most adaptable and typically perform well as spring, summer and fall crops.

I want to quickly discuss the growing culture of spring and summer radishes and then later in the podcast I will revisit the specific needs of the fall varieties.

In general, growing radishes is super simple. They are direct-seeded into the garden beds, so there is no need to mess with transplants. Direct seeding also facilitates easy succession planting because all you need are the seeds and some space in your garden. For a continual harvest of radishes, seed short rows every 2 weeks during the growing season.  Radishes can be harvested in as little as three weeks after sowing.  

Because they grow so quickly, radishes are a great crop to plant alongside longer season crops. You can interplant them with brassicas, squash or nightshades and get a quick harvest while your long season transplants are just starting to size up. Keep in mind that radishes are a brassica family crop, so practice crop rotation whenever possible and refrain from planting them in areas of the garden that may be affected by brassica diseases such as clubroot.

Radishes will grow in a wide range of climatic conditions, but most grow best in cool weather, around 50 F to 65 F. You can direct seed them as early as 6 weeks before your average last frost in the spring and all the way up until about 6 weeks before your average first frost date in fall. You’ll seed them about ½” deep and thin them to 1-2” spacing after they’ve germinated. Of course, you’ll want to make sure to eat your thinnings. Try them on top of a salad or in a sandwich.

Like all root crops, proper thinning will provide you with the best quality crop, but radishes are a little more forgiving than other crops like beets or carrots. Often, if radishes are a bit crowded, they will simply push each other out of the way and you can harvesting the largest roots first and leave the smaller ones to continue to sizing up for another week or two.

In the middle of summer, hot weather can reduce quality, making the roots pithy and can also increase the pungency or spiciness of the radish. If you find that your summer temperatures are too hot for radishes, often evidenced by bolting, just stop planting for a while in the peak of summer and resume your successions when things start to cool down again a little bit. Some, more heat tolerant “summer varieties” like Summer Cross do exist. Check descriptions in your seed catalog if you are looking to select different varieties for spring, summer and fall plantings. In our climate, we find that many spring radish types will grow well throughout the summer season.

Winter radishes behave a bit differently than the spring and summer types. Winter radishes will typically grow more slowly, taking up to 2 months or more to reach maturity. They will also produce larger roots and some of these have atypical shapes, like the cylindrical daikon. Winter radishes will also hold their quality much longer than spring and summer varieties. You may see winter radish types referred to as Oriental, Daikon, Japanese, Chinese, or Spanish radishes. Like all late season crops, winter radishes need to be planted in summer for fall harvest.

You’ll want to plant most winter varieties so that they mature around your first fall frost date, so you might want to have them all in the ground about 6-8 weeks before your expected first frost. A light frost will improve the flavor and texture of most winter varieties. Since winter varieties are typically larger than other radishes, they need more space, so you’ll want thin them to about 4-6-inches depending on the variety.

So if you are interested in expanding your radish horizons, I encourage you to start exploring different types now. Get some seed on hand and start to get your fall crop in the ground.

Here is a quick list of my favorite radish types, I’ll have these listed on our blog for easy reference after I post this podcast.

For spring and summer:

• Cherriette (a typical small red round type that seems to always grow perfectly)

• D’Avingon (a french breakfast type which is longer and narrower with a two-tone pink and white color).

• Easter Egg radishes (which is a mix of different colors that can all grow together)

• Shunkyo (which is a narrow Chinese type that can be grown in spring).

For fall:

• Nero Tondo and Round Black Spanish (black radish)

• Misato Rose

• Daikon radishes

Well, that’s it for this week. Remember, you can subscribe to our podcast via iTunes and we’d love to hear what you think, so leave us a review!