Honey bee pollen foraging in relation to flowering phenology of biennial caraway (Carum carvi L.)

Biennial caraway (Carum carvi L.) is a specialty spice crop in Saskatchewan, yet little was known about fundamental agronomic traits, such as its flowering phenology, plant density, attraction to potential pollinators, and prospective honey yield. At five commercial fields in 1998 and 1999, biennial caraway flowered for 7 wk, beginning in late May or early June and finishing by early to mid-July. Under optimal conditions, and assuming intense foraging activity by honey bees (Apis mellifera L.), caraway might yield 70–134 kg honey ha–1. However, weights of colonies near fields of caraway (0.47–4.2 hives ha–1) changed little while honey bees were predominant foragers on that crop. Then, in the second half of the caraway flowering period, when honey bees had almost deserted those fields as indicated by observation and pollen-trap analyses, hive weights rose steadily due to a switch to nearby crops of canola (Brassica spp.) and sweet clover (Melilotus spp.), which had begun to flower. Whereas biennial caraway is rated as negligible to only moderate for its honey potential in Saskatchewan, 83% of honey bees visiting caraway florets gathered pollen. Moreover, caraway pollen entering hives averaged 11% of total pollen (dry weight) over the entire flowering period of the crop, but 36.5% during the first half of flowering phenology, suggesting that biennial caraway may constitute a valuable source of protein for honey bees, particularly during colony build-up in spring. Key words: Caraway (Carum carvi), flowering phenology, hive weights, honey bee foraging, honey potential, pollen-trap collection