90-100 days. Long Island Improved Brussels sprouts seeds. Brassica oleracea var. gemmifera. Non-GMO. Brussels Sprouts can be grown in colder climates, and the crop is very tolerant of frost. While the sprouts can take up to one hundred days to reach maturity, they make great crops to grow during the winter and colder months of the year. Brussels Sprouts have been cultivated since as early as the 1500’s, and have a strong and bitter taste, similar to that of cabbage.