Table 2. Nectar sugar production rates for plant species flowering, near Würzburg, during the period of bumblebee colony foraging performance experiments.
| flower species | bee-subjective colour | nectar production (µg/24 hours) |
| Papaver dubium L. | uv | 0 |
| Papaver rhoeas L. | uv | 0 |
| Papaver somniferum L. | uv | 0 |
| Anagallis arvensis L. | uv-b | 0 |
| Campanula glomerata L. | uv-b | 156 |
| Campanula patula L. | uv-b | 75 |
| Cynoglossum officinale L. | uv-b | 1358 |
| Dactylorhiza majalis (Rchb.) P.F.Hunt & Summerh. | uv-b | 0 |
| Echium vulgare L. | uv-b | 1537 |
| Impatiens glandulifera Royle | uv-b | 11312 |
| Lunaria rediviva L. | uv-b | 97 |
| Lupinus polyphyllus Lindl. | uv-b | 0 |
| Lythrum salicaria L. | uv-b | 794 |
| Onobrychis viciifolia Scop. | uv-b | 58 |
| Salvia pratensis L. | uv-b | 466 |
| Salvia verticillata L. | uv-b | 520 |
| Vinca minor L. | uv-b | 731 |
| Allium schoenoprasum L. | b | 505 |
| Calluna vulgaris (L.) Hull | b | 202 |
| Epilobium angustifolium L. | b | 2332 |
| Epilobium hirsutum L. | b | 240 |
| Geranium robertianum L. | b | 811 |
| Glechoma hederacea L. | b | 160 |
| Lamium maculatum L. | b | 267 |
| Lamium purpureum L. | b | 114 |
| Lychnis flos-cuculi L. | b | 529 |
| Medicago sativa L. | b | 408 |
| Pinguicula vulgaris L. | b | 0 |
| Prunella vulgaris L. | b | 332 |
| Salvia nemorosa L. | b | 318 |
| Silene dioica (L.) Clairv. | b | 714 |
| Stachys palustris L. | b | 1384 |
| Stachys sylvatica L. | b | 898 |
| Symphytum officinale L. | b | 1061 |
| Syringa vulgaris L. | b | 500 |
| Teucrium chamaedrys L. | b | 221 |
| Thymus pulegioides L. | b | 87 |
| Trifolium pratense L. | b | 400 |
| Vicia cracca L. | b | 723 |
| Vinca minor L. | b | 546 |
| Viola canina L. | b | 97 |
| Cardamine pratensis L. | b-g | 745 |
| Centaurea jacea L. | b-g | 187 |
| Filipendula ulmaria (L.) Maxim. | b-g | 0 |
| Knautia arvensis (L.) Coult. | b-g | 141 |
| Lamium album L. | b-g | 467 |
| Linaria vulgaris Mill. | b-g | 1736 |
| Lunaria rediviva L. | b-g | 75 |
| Rosa canina L. | b-g | 0 |
| Sambucus nigra L. | b-g | 0 |
| Silene album (Mill.) E.H.L.Krause | b-g | 933 |
| Symphytum officinale L. | b-g | 1765 |
| Trifolium hybridum L. | b-g | 187 |
| Trifolium repens L. | b-g | 129 |
| Lathyrus pratensis L. | g | 216 |
| Lotus corniculatus L. | g | 330 |
| Agrimonia eupatoria L. | uv-g | 0 |
| Brassica napus L. | uv-g | 362 |
| Helianthemum nummularium (L.) Mill. | uv-g | 0 |
| Lamium galeobdolon (L.) L. | uv-g | 1360 |
| Melilotus officinalis (L.) Pall. | uv-g | 88 |
| Sinapis arvensis L. | uv-g | 1324 |
| Verbascum densiflorum Bertol. | uv-g | 0 |
The 63 plant species included all flower during this period (June and/or July) according to published phenological data [29], and are divided into six bee-subjective colour categories (uv = ultraviolet, uv-b = uv-blue, b = blue, b-g = blue-green, g = green and uv-g = uv-green). Data presented are mean amounts of sugar produced (µg in 24 hours) per species, averaged across at least 30 flowers per species [17], [27].