Cross‐Pollination Studies Involving Three Purple‐Flowered Alfalfas, One White‐Flowered Line, and Two Pollinator Species 1

White‐flowered alfalfa was equal to colored‐flowered alfalfa in attracting nectar‐collecting honeybees, but less attractive for pollen‐collecting leaf‐cutting bees. Comparisons of white‐ and colored‐flowered alfalfa for percentage of stainable pollen, nectar sugar per flower, and pollen extrusion were not significantly different. Cross‐pollination was higher for honey bees than leaf‐cutting bees (45.4%:41.2%), but seed production was higher for leaf‐cutting bees (315 g:265 g). Cross‐pollination but not seed yield was affected by the bee by variety interaction. This highly significant interaction occurred because cross‐pollination of white‐flowered alfalfa paired with ‘Uinta’ alfalfa pollinated by leaf‐cutting bees was low, but high when pollinated by honey bees. The percentage of crossing on spaced white‐flowered alfalfa plants as determined by colored hypocotyls was 54.9, with a standard error of 1.8. This compares with a value of 74.4% for hand‐crossed seed without emasculation.