Brussels sprout is a cultivar of wild cabbage grown for its edible buds. The leafy green vegetables are typically 2.5–4 cm (0.98–1.6 in) in diameter and look like miniature cabbages. The sprout is Brassica oleracea, in the “gemmifera” group of the family Brassicaceae. Although named after the city in Belgium, few historians believe the plant originated there.
Brussels sprouts grow in heat ranges of 7–24 °C (45–75 °F), with highest yields at 15–18 °C (59–64 °F). Fields are ready for harvest 90 to 180 days after planting. The edible sprouts grow like buds in a spiral along the side of long thick stalks of approximately 60 to 120 cm (24 to 47 in) in height, maturing over several weeks from the lower to the upper part of the stalk. Sprouts may be picked by hand into baskets, in which case several harvests are made of 5 to 15 sprouts at a time, by cutting the entire stalk at once for processing, or by mechanical harvester, depending on variety. Each stalk can produce 1.1 to 1.4 kg (2.4 to 3.1 lb), although the commercial yield is approximately 900 g (2.0 lb) per stalk. In the home garden, “sprouts are sweetest after a good, stiff frost.”
Brussels sprouts are a cultivar of the same species that includes cabbage, collard greens, broccoli, kale, and kohlrabi; they are cruciferous. They contain good amounts of vitamin A, vitamin C, folic acid and dietary fibre. Moreover, they are believed to protect against colon cancer, because they contain sinigrin. Although they contain compounds such as goitrin that can act as goitrogens and interfere with thyroid hormone production, realistic amounts in the diet do not seem to have any effect on the function of the thyroid gland in humans.
Brussels sprouts, as with broccoli and other brassicas, contains sulforaphane, a chemical believed to have potent anti-cancer properties. Although boiling reduces the level of the anti-cancer compounds, steaming, microwaving, and stir frying does not result in significant loss.