A single stalk of this variety can bear 50-100 dark-green Brussels sprouts over an extended period. Compact plants produce sturdy spikes with edible florets that mature from the bottom up and take on sweeter tones after a light frost. Introduced in the 1890s Long Island Improved is open-pollinated. Mature 90 days from transplant. Brussels sprouts are members of the cabbage family. This hardy, cool-season vegetable requires temperatures below 70 degrees Fahrenheit to produce good-quality, flavorful sprouts. In mild, Mediterranean climates, plant spouts during the months of June through September for a late fall or winter harvest. The Brussels sprout plant is grown as an annual vegetable, although it is a biennial. Growing upright, the sprouts develop along the stalk of the plant in the leaf axils.