What is your first frost date? John

Here is a link that might be useful: John's Journal

The web has the date at 11/05. I would direct seed 12 weeks before that date. John

Here is a link that might be useful: John's Journal

Depending on the cultivar, broccoli may produce one head or hundreds of florets. The major cultivars available to home gardeners will produce a large main head followed by smaller sideshoots. Sprouting broccoli cultivars are also available which start with a copius amount of sideshoots.
My average first frost is around Thanksgiving, so I find a cool place to start plants in late July and begin transplanting just after Labor day. The only critical factor is heat. Broccoli just can't handle hot soil associated with triple digit temps for very long.
Main head {{gwi:50219}}
Sideshoots {{gwi:54476}}

@ John: Good question thank you. Usually we don't have any frost until mid- Feb. Thanks for the link to your journal you have some neat plants there!

@farmerdilla: Nice! Thank you for those pictures, what a gorgeous plant!

I have started broccoli under lights the past two years, and they do fine except they are leggy and some have bent stems that lie along the ground for an inch or two before continuing upward. The lights are only 2 inches or so above the plants, so I don't know why this would happen (except I just saw on another post that I should be turning the lights off at night). My question is: can I bury the horizontal section of stem when transplanting, or will that hurt the plant?

As long as they are still indoors and at risk for damping off, you might heap some dry seed starting mix over those vulnerable basal stems. Then water from the bottom as much as you can. Some physical reinforcement will serve the plants well during hardening off. They will grow fast once they get outside in good light, but still I'd heap a little soil up around them when setting out, and then use cloches for a few days after transplanting to shield them from twisting winds. Those stretched out basal stems are weak spots to accommodate, that's all. The plants should do fine.

For the second time ever, I started some broccoli in cold frame this year and have planted them.
Now they are over a foot tall but no heads at sight. Will they grow heads before it gets real hot?
BTW, I have planted them some spot that get a few hours of sun and mostly shaded,
with cooler air coming from the wooded area.

Just remember that it will take longer for them to mature in the shortening days of the fall. I planted mine out in mid August last year. September and October was extremely cool, cloudy and rainy. I finally harvested all my Broccoli in Mid November. I only got to harvest all the main heads, there was very little side shoot production. It snowed 6-8 inches the following week and the plants finally gave up.

Jay

Why would you start seeds indoors at that time of year? I direct sow when I first feel that hint of Fall in the air. But you may need to shade the seedlings if they are in direct sun and daytime temps are high.

lnewport : Thanks for asking the brocolli questions (single head/offshoots)...been sorta embarrassed myself to ask the question...gotta a question to add: I"m in zone 6, have access to grow lights, though don't have ready access to the garden i'll be in the fall...Should I start my seeds under lights at the end of july/august? Also: How to tell if you have a shooting off the sides cultivar?

One more brassica question: Also considering growing cauliflower and brussel sprouts...do their indoor start dates coincide with broccoli?

Cauliflower and broccoli have similar growing seasons. Brussels sprouts have a much longer growing season ( 1 - two months depending on variety so You you will need to plan accordingly.

For spring broccoli, cauliflower, and cabbage I start seeds in a cold frame in midwinter. They are also good candidates for winter sowing. Never used lights or indoor starting. Fall plantings are started in an open bed in a sheltered cool spot ( partial shade) I have never been able able to get the timing right for Brussels sprouts here in Georgia so I no longer grow them. Back in Virginia I set them in early July for Novemeber harvest.
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I had always heard that broccoli was a cool weather crop. I was surprised to see home depot had seedlings back in march. I planted them not knowing, I now know that the likely hood of mine producing are slim, but it definately attracts the caterpillars! So far they are attacking the broc and the radishes and leaving everything else alone. I am gonna start from seed in July indoors so I can get a jump on the season for fall!

I'm new to growing cool-season crops, too. I started my broccoli indoors, under lights, in early March. The plants are nice and healthy, but they're still not very big, and definitely no hint of heads. So that means I probably won't get a crop from these plants? Too bad, I was looking forward to it.