This year I planted my broccoli transplants in mid-April. They are just heading up now. I've planted as late as mid May (transplants) and still gotten decent size heads. I think your goal of sometime between April 15 & May 1 is good. A couple years ago we had a particularly mild start to winter - some frosts & light snow but nothing serious. I was picking broccoli until January 6! Not the norm but possible.

I've never tried a fall crop.

I would try a fall crop. Amend the soil with compost and composted manure and then mulch with 3 - 4 inches of leaves
or INTERBAY mulch ( cover with burlap if you can ) until August.

Do you have seed ? I am starting cole crops soon for fall from seed.
If the weather gets above 85F I bring inside in front of
a bright window.
Grow plants outside if weather is below 85F but protect
from mid day sun a bit.
Transplant to beds in early - mid August or 6 - 8 weeks
before first fall frost. Plant your transplants right through the leaf mulch and if August is hot ( 85 + )
cover with the burlap in the middle of the day and uncover
late afternoon till next morning.

If you cant do it this year then next year try and plant in
an area that is protected from sun in the late afternoon so
they will not bolt too soon.

( one more thing, I add crushed eggshells to my cole crop
beds for calcium and foliar spray with Epsom Salts )

The way I explained it might seem like too many steps but
it's not really. Maybe others can explain easier :-)

Good Luck

I've only grown Broccoli 2x and both times I did 'Green Goliath' using the wintersow method (see Winter Sowing Forum for more info). Last year I sowed the seeds 3/25 with germination by 3/30; seedlings planted out into the garden by May 01. Heads were harvested around July 10th as I recall. GREAT resistance to heat and they were yummy yummy!

This year I started the seeds on 3/23 with germination by 4/9. Seedlings were planted out on 4/26. All my wintersown containers are in full sun from start to finish. Our last frost date here is usually between 5/10-5/15.
Here are a few pics....
July 9th 2007....excuse the carrot tops peeking thru :)
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April 24th....wintersown containers including Broccoli far left
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May 20th
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June 12th
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I planted a row of Broccoli, a staggered row of Lettuce 'Merveille des Quatre Saisons' followed by a staggered row of Collard 'Georgia'. Inter-planted with Calendula officinalis nana 'Citrus Cocktail' and dwarf Marigolds. Haven't had any cabbage worms or aphids yet :)
This is how it looked earlier on Just laid down more grass clippings (dried out a few days first)last week. It's working on really well. I try to wait on thick mulch until seedlings are a little bigger; less cover for slugs and such
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I like to grow Green Goliath & Calabrese varieties. I tried Premium Crop one year and was not impressed. It had small heads & fewer side shoots than Green Goliath.

Vera, great pictures. I am especially interested in your milk jug "greenhouses." What a great idea. Will try that next Spring. Thanks.

I, too, admired the milk jug greenhouses. I don't get milk in gallons, but I bet any kind of white or semiclear jug would do. I assume they don't get too hot? Great way to recycle, too.