SUMMARYThe effects of topping at different dates, and of different plant populations on dry‐matter production and distribution in Brussels sprouts were studied. Total dry‐matter production per unit area was unaffected by either topping or density. Leaf area was decreased by topping, resulting in a temporary increase in net assimilation rate. Topping resulted in a redistribution of dry matter; that which would have formed new stem and leaf tissue was directed into sprout production.Increasing plant density did not affect the distribution of dry matter but increased the number of smaller sprouts. The apparent optimum plant spacing in this series was 21×21 in (53×53 cm). At maturity assimilation approximately balances respir