A Long Season, a Tall Single Stalk, and a Bottom-Up Harvest
Brussels sprouts grow as a single, increasingly tall stalk, and University of Georgia Cooperative Extension recommends a management step with no equivalent in other brassica-growing guides: pinching or topping the plant once it reaches about 24 inches tall, to redirect the plant's energy from continued vertical growth into sprout development instead.
Harvest itself works differently, too. Rather than a single cut like a head of broccoli or cabbage, sprouts are picked from the bottom of the stalk upward over weeks to months as the season progresses -- and University of Minnesota Extension notes plants can stay productive in the garden "as long as temperatures remain above 20°F," making this one of the most cold-tolerant crops on this page.
Cultivar maturity times vary meaningfully and are worth knowing before you plant: University of Georgia Cooperative Extension lists Long Island Improved at about 90 days, Jade Cross at about 100 days, and Diablo at about 110 days -- all substantially longer than the 55-70 days typical of broccoli or cauliflower.
Why Spacing Matters for Brussels Sprouts
Because the plant occupies its spot in the garden for so much longer than related brassicas, adequate spacing has more time to matter -- a slightly crowded broccoli planting is only crowded for 60-odd days, while a slightly crowded Brussels sprouts planting stays that way for a full season.
The wider between-row figures some extension sources give (up to 36-42 in., versus 24-36 in. for broccoli or cabbage) plausibly reflect the mature plant's greater height and bulk over that long standing time, though no source we found states an explicit airflow rationale for the wider figure the way tomato sources do -- worth noting as an inference rather than an established fact.
