They will go to seed, because they will react to the lengthening days. As the days shorten in the fall they wont go to seed.

You can plant them in early Spring & pull/pick them when they are ready.
If you wait till November, then they will not taste good.
Pithiness &/or a very strong flavor can develop if these crops are left in the ground during hot weather.
You should sow seeds as soon as soil is loose & thawed in early Spring.

Agree with Masbustelo, even I think they will seed if planted in spring and waited till November.

I've only grown one variety, Hakurei, which is meant to be picked small. But I did spring grow it, and it was flavored very nicely. You can tell when it is gettng too hot for them, they start wilting from heat stress pretty easy. I wonder if I have time to get another little sowing in now...

So if I plant turnips on June 21, I will get them as big as possible without them bolting?

I am curious. Why do you want big turnips?

I am just exploring all possibilities. I always bleed myself grating them, so bigger better, and besides, in July I am often traveling. I was hoping for one spring planting (together with, say, beets, parsnips and carrots) with Fall harvest because I have space but not time. One planting means one trip to the garden for daily watering, one big weeding, one fertilization where needed, etc.

Jim Crockett - the original public television 'Victory Garden' host - planted in March and harvested at the end of May. That's in Boston, so it's at the same time as our earliest planting - peas, spinach, etc.

I have to disagree about turnips bolting in response to long days. Turnips are biennial, which means they bolt in their second year of growth. This has nothing to do with day length.

I believe turnips do best in cool temperatures though. So, either early or late planting should work.

Jim

But the question is: will early planting and late harvest work. Turnips are one of my winter staples, but in the summer I have other interests. There is drip irrigation and plenty of garden space. I assume Jimster is saying they will go dormant during the summer, and resume growth in the Fall, while maintaining eating quality. I am of course talking about purple tops, not the super-fast Hakurei.

Glib The traditional planting date for turnips in our zone has been July 30th, but it would be an interesting experiment to start them after the equinox and see what happens.Also try peeling and slicing them and eat them with a little salt, fresh.

"I assume Jimster is saying they will go dormant during the summer, and resume growth in the Fall, while maintaining eating quality."

No. What I had in mind was to grow them either as a spring crop or a fall crop, not to plant early and harvest late. Sorry if I misunderstood or confused the issue.

Jim