Broccoli is a hardy vegetable that grows best in cool weather.
In most areas there is not enough time to grow broccoli from seeds before the weather gets too hot.
Start seeds indoors 12 weeks before the frost date, or purchase transplants.
Transplants are ready when they have 4-6 true leaves. Harden off and transplant outside 6 weeks before the frost date.
If you live in a climate with hot summers and/or a short fall, choose varieties that mature quickly.
Start seeds indoors 14 weeks before the first fall frost date, or purchase transplants (if available).
Transplants are ready when they have 2-4 true leaves. Harden off and transplant outside 9 weeks before the frost date.
The plants will mature more slowly in the fall because the days are shorter, but since they can tolerate freezing temperatures, you can continue harvesting after the first fall frost.
If you live in a mild climate with a late or no fall frost date (after Nov 1), you might be able to plant broccoli from seed and grow it all during the winter.
Soil and Fertilizer
Broccoli grows best in a rich soil; amend with lots of compost and fertilizer (chemical or organic) at planting and twice during the season.
Fertilizer: 16-16-8 at planting, 21-0-0 when heads are 1 1/2″ in diameter, and again after harvesting main head.
Harvest before the flower buds open, when they are still tight and the head is 6-10″. Cut off 6 inches of stem along with the head.
After the first harvest, fertilize and continue to water. Side-shoots will appear and produce several smaller heads.