Broccoli resembles cauliflower, a different but closely related cultivar group of the same Brassica species.

[6] Broccoli resulted from the breeding of landrace Brassica crops in the northern Mediterranean starting in about the sixth century BCE.

[7] Broccoli has its origins in primitive cultivars grown in the Roman Empire and was most likely improved via artificial selection in the southern Italian Peninsula or in Sicily.

[9] After the Second World War, the breeding of the United States and Japanese F1 hybrids increased yields, quality, growth speed, and regional adaptation, which produced the cultivars commonly grown since then: 'Premium Crop', 'Packman', and 'Marathon'.

[further explanation needed] The inflorescence grows at the end of a central, thick stem and is dark green.

Broccoli is collected by hand immediately after the head is fully formed yet the flowers are still in their bud stage.

[16] Broccoli cultivars form the genetic basis of the "tropical cauliflowers" commonly grown in South and Southeastern Asia, although they produce a more cauliflower-like head in warmer conditions.

[18] Secondary producers, each having about one million tonnes or less annually, were the United States, Spain, and Mexico (table).

[3] The perceived bitterness of cruciferous vegetables, such as broccoli, results from glucosinolates and their hydrolysis products, particularly isothiocyanates and other sulfur-containing compounds.

[27] Preliminary research indicates that genetic inheritance through the gene TAS2R38 may be responsible in part for bitter taste perception in broccoli.

[28] The larvae of Pieris rapae, also known as the "small white" butterfly, are a common pest in broccoli and were mostly introduced accidentally to North America, Australia, and New Zealand.