Ordinary zucchini fruit are any shade of green, though the golden zucchini is a deep yellow or orange.[6] At maturity, they can grow to nearly 1 metre (3 feet) in length, but they are normally harvested at about 15–25 cm (6–10 in). In botany, the zucchini's fruit is a pepo, a berry (the swollen ovary of the zucchini flower) with a hardened epicarp. In cookery, it is a vegetable, usually cooked and eaten as a savory dish or accompaniment. Zucchini occasionally contain toxic cucurbitacins, making them extremely bitter, and causing severe gastero-enteric upsets. Causes include stressed growing conditions, and cross pollination with related species such as cucumbers and ornamental squashes. Zucchini descends from squashes first domesticated in Mesoamerica over 7,000 years ago, but the zucchini itself was bred in Milan in the late 19th century.