A hardy, cool-season vegetable, broccoli is full of vitamins A and D. Traditionally, broccoli was grown as a spring and a fall crop. The development of new heat-tolerant varieties, however, means that broccoli is enjoyed in summer, too. Broccoli plant size affects spacing, and helps a grower identify when the plant is ready for harvest.
Broccoli plants grow upward, rather than out. At maturity, these plants grow up to 2 1/2 feet tall. To ensure broccoli plants have enough room to grow, leave 12 inches between plants in all directions.
Broccoli plant head size varies by variety grown, growing condition, season and care. When plants are ready to harvest, broccoli heads range from 4 to 6 inches in width, or greater. The main or central heads are largest; smaller or late-developing side shoots are often only 1 to 2 inches across. Central heads weigh up to 1 lb., with smaller side shoots weighing no more than 1/3 lb.
Broccoli plants appear yellow and exhibit poor growth if not given the right care from the start. Planting too late or too early in the year contributes to small plant size. Seedlings that were mistreated develop poorly, so purchase quality plants from a grower you trust. Fertilizing broccoli at planting time helps get plants off to a good start, but won't be enough to get poor quality plants to reach maximum growth.
In general, broccoli plants take around two months to mature. The plants are to be harvested before flowers develop, and are generally harvested for several weeks. Cutting the main heads first spurs growth of side shoots, which are picked later. When cutting broccoli heads from the plant, cut 5 to 6 inches of stem along with the head.