That Daikon may not do well in Spring for you, have you tried an Autumn crop?

I always plant in December, and look to harvest in March or April. Not sure what would make fall better. Our extension says it's a winter crop. Climactically, our winter is like fall in most other places.

In Northern climates they are known as "Winter Radishes", they are grown to get big by Winter, then pulled before Spring. You are growing them into Spring, so maybe they are getting ready to flower. You could eat the seed pods. You just need to figure out the timing that is best for your latitude.

Concur. Radishes are a cool weather crop. Daikons average about 50 days DTM so if they have space and the high temps hold off, you may still get a crop.

Like I said, I planted these in winter. At the end of December. Two months after I planted them, in March, the roots were pencil thin. That's the date of last frost. I waited until now, hoping they would increase in size. Understandably, the plants just flowered, and the roots didn't get nay bigger. Not going to get any colder here, so maybe these things are just not suited at all to my climate? Our extension service would disagree, however. Do I understand from you that I should have planted in November? It certainly isn't warm here in January and February, and it can be warm in October. Not a lot of flexibility in timing.

Yes, you don't have a Japanese like climate but you can experiment. Why not plant in November whenever you think the temps have stopped being very hot, and let them grow before the daylight gets longer in February. The longer days means Spring is coming up, so the plant might grow more leaves instead of bulking up the root. It grows in Winter, you don't have to wait until the end of the year to plant.

Sorry, but I can't believe that a few weeks difference in planting date is going to make me get substantive Daikon radish roots. Day length? The day length in February is barely half an hour over what it is in January. I'll ask at my extension service.

I'm just saying you are fighting against the nature of the Radish, since you don't get good results. Go ask your extension, I'm sure they love to hear from you.

I also may be fighting against the nature of the soil. I'll let you know what I find out.

OK, got an answer back from an A&M Agrilife senior horticulturalist. (They're always fast!) The answer is that nitrogen fertilizer will have NO EFFECT on root formation of Daikons. Hours of sunlight are irrelevant. Daikon radishes are extraordinarily sensitive to heat, though. Interesting that other root veggies are not. Warm temperatures at maturity will cause bolting and tiny roots in Daikons. I planted in late December, hoping to harvest in March. Now, around here, our last frost is beginning of March, but we can get warm afternoon temps then, and even in February. So planting MUCH earlier, as in September or October, when it can still be warm, will put maturity in the coldest months. So that's what I'll do later this year. Also, important to select heat tolerant varieties. Giant White, Minowase, French Breakfast and (amusingly) Icicle are among those. I don't remember what variety I planted this year.

By hours of daylight I meant the season cycle. You are growing from cold Winter to Spring so the plant tends to respond by wanting to flower instead of making the root large. By growing from Autumn to Winter the plant hopefully should make a larger root while the days get shorter and colder, so as to save energy for Spring.

The issue is simply temperature at maturity.

OK, the ones I planted were Miyashige White, which are not anywhere identified as "heat tolerant". It says on the package "Sow in summer for fall harvest". Duh? Well, this is from Botanical Interests, which is in Colorado. When you live down where I do, you take planting instructions from northerners with a major grain of salt.

Just for information. The only Daikon that I have spring success

with is New White Spring. Very dependable for April harvest here.

I do see that New White Spring has a lot of bolting tolerance. Bolting shuts off root formation, so that's useful to know.

A few varieties of daikon can be grown successfully during spring but for the most part they are a fall/winter crop. This means they are meant to be harvested during fall/winter. They aren't meant to be grown during winter, and being biennial if they are planted too late and left to overwinter they will just bolt instead of growing roots. As you have found out.

"OK, the ones I planted were Miyashige White, which are not anywhere identified as "heat tolerant". It says on the package "Sow in summer for fall harvest". Duh? Well, this is from Botanical Interests, which is in Colorado. When you live down where I do, you take planting instructions from northerners with a major grain of salt."

It's hard to fight against natural growing cycles of plants. In the same way one wouldn't plant garlic in June and expect a crop of large bulbs in October, one shouldn't expect a good crop of daikon when planted at the wrong time. In the northern US we would sow them in late July or early August for an October/November harvest. In the southern US you would simply adjust that timeline a bit and wait until the full heat of summer starts to subside before sowing. That could mean sowing anywhere from September to November depending on location (as your extension service points out). If you try again later this year with Miyashige White and plant at the proper time I am sure you will have more success with it.

I find two of the extension's variety recommendations odd. French Breakfast is definitely not a daikon radish, and I have my reservations about Icicle. Icicle is a white radish that gets around 6 inches long and takes around 30 days to mature. I'm not sure I would classify it as a daikon...

Rodney

Yes, as I said earlier, I think it is now clear that planting in September/October is the way to go for me. The reason being that I want maturity in mid-winter here. The best planting time is defined not by when it's cool enough, but by when DTM is going to happen when it is surely cool. Indeed, Miyashige White is probably heat-tolerant enough for that, and I still have some seeds.

It is just very curious that other root crops are not anywhere as particular about planting time as these seem to be. Beets don't like to be planted in heat, but they have no trouble maturing in heat.

True that French Breakfast aren't all white, but they are elongated and carrot-like in shape like a true Daikon. I believe "Icicle" is just an English name for a white elongated radish, which is a Daikon. Now, I do find it hard to believe that you can get a six-inch long radish in 30 days.

Radish seedlings do not grow as well in hot weather, so that is an issue. They tend to grow rather elongated and flimsy at first, but I'm sure you will say that is wrong.

French Breakfast and Icicle are quick European elongated radishes, they are picked in a month in Spring time in the North, not like a traditional Daikon, but you should try them should be easier. Unless you were specifically looking for Daikon types. Of course all that is wrong, sorry.