Depending on the variety, they wouldn't start to form heads until late July-early August. The heat will cause them to bolt and go to seed. If leaves are what youre after, thats about all that what you will get, but i'm pretty sure when they bolt the flavor of the leaves will turn bitter. Here in Jersey we have to plant them in late March - early April so we can harvest the heads before the heat sets in.

It is late to be planting out broccoli, but because of the weather I won't be planting mine out until this weekend. There's a good chance you'll still get smaller heads and side shoots after that. The leaves should be fine to eat as greens prior to the broccoli starting to head. After that they may become bitter.

I know they like cool weather, and it's going to be hot for at least the next week - I don't know whether to hope June is hot (for the tomatoes and peppers) or cool! But if I want to try to get some broccoli leaves from these starts, where (how much sun, maybe in pots?) should I plant them? Or should I not even bother taking them out of the flat?

I wish I had gotten these in April - though they might have rotted in May like my lettuce did...

I plant my spring crop of broccoli on the side of my garden that receives some afternoon shade. Though night time temps go down, we've had a couple spells where the days went up to the 90's and they never bolted. (Can't remember if they'd even formed heads yet when that happened.) But yes, I'd shoot for the coolest spot you can find.

I'm wondering if there is a way I can keep them in 4" pots in the house and transplant in July for a fall harvest? Or more likely, they will die in the July heat...

Unfortunately, "cool" might mean "shady" and I thought broccoli needed sun? I've never grown it before.

Yes cool means shade. You aren't going to be able to create the ideal conditions now. It is simply too late. Nor will they survive inside in 4" pots till July.

The best you can hope for is to plant them to get some leaves until they bolt (send up a flower/seed stalk) and than means avoiding the afternoon sun and the highest air temps. The rest is a lost cause for all practical purposes.

So to grow for leaves and to delay bolting, plant them in the shade as loribee suggested. If they get some early morning sun so much the better or if you put them in containers, then you can move them everyday from early morning sun to after noon cooler shade if it is worth the trouble to you.

Dave

Yes, remember that winter crops are accustomed to shorter days, so they don't need as much sun as the summer veggies do.

You may be fine. Broccoli if given sufficient water will tolerate temps in the high 90's as long as you keep the soil temps down. I know folks in the north grow long season broccoli. As for bolting, its suppose to bolt, we eat the flower heads. Premature heading does gives small heads, just treat it as sprouting broccoli and use those little heads before the flowers open.
{{gwi:47157}}

Gave 4 to my dad, kept 20 (and transplanted them into 4" pots). They were doing so well on the north side of the garage that I transplanted half of them today over on west side of house, but close to trees, so they get some late AM sun but are shaded all afternoon. They were getting potbound 2 weeks out of the flat.

How can I tell if/when they are starting to head?

I may just plant the other half in large pots being vacated by my tomatoes and lettuce this week, keep them on the north side, just for comparison.