Summary.Plants ofChenopodium albumL. were grown at a range of different densities in each of three years. The stem diameter, the number of main branches and the size and number of leaves decreased with increasing density as did weight and leaf area per plant. The dry‐matter yield per unit area increased with density up to 576 plants/m2in two of the three trial years. The proportion of the seed yield relative to the total yield was higher in the leas dense than in the dense stands, or was almost constant. Density did not affect the seed yield per unit area, but seed yield per plant fell as density increased. Maximum seed production was 41 900 per plant and the mean seed yield over the three years was 8300 seeds per plant. The percentages of nitrogen, phosphorus, potassium and calcium were highest when the plants were at an early stage of development. The proportions of these elements in the dry‐matter yield decreased with increasing age of the plants. The density of the stand did not affect the percentages of elements but the total amounts per plot were greatest at the flowering stage and in the denser sta