Spacing and ‘Bolting’ of Vegetables

LANDAU¹ has pointed out that the incidence of bolting in onions is affected by the spacing of the plants. He found that more bolting occurred on the outside rows of experimental plots than in the centre, and suggested that competition for light constituted one of the determining factors. That this effect of spacing on bolting is not an isolated phenomenon is shown by results which our experiments over a period of two years have yielded. In these experiments on beet, carrots and shallots the plant spacings have been deliberately altered by varying either the thinning or planting distance, and some of the results obtained are tabulated below. The rows of beet and carrots were in all cases 18 in. distant.