BIRCH. (Betula) Small greenish or golden-yellow flowers; appearing with or before the leaves in spring; wind-pollinated; mostly trees.
COCKLE-BURR. (Xanthium canadense) Coarse weed, obscure greenish flowers, produced all summer; bees work them for pollen in the early fall. They contain a little nectar.
CORN. (Zea mays) Wind-pollinated; bees gather pollen from the spindles; very heavy pollen yielder.
ELM. (Ulmus americana) Small purple flowers which appear in the spring, and are wind pollinated. They are visited by great numbers of bees for pollen.
HEMP. (Cannabis sativa) Small flowers pollinated by the wind. Is only of local importance, especially around Waupun.
MULLEIN. (Verbascum) Very common; bright yellow flowers. Most important in Northern Wisconsin. A part of the species are nectarless; others contain some nectar.
OAK. (Quercus) Small greenish or yellow flowers wind-pollinated; honey dew is found on the foliage of some species.
PIGWEED. (Chenopidium) Goosefoot. Garden weeds, also amaranth, called pigweed (Amaranthus retroflexus) coarse wind-pollinated weeds in cultivated ground; flowers in large clusters, of some value for pollen.
PLANTAIN. (Plantago) Partly pollinated by the wind and partly by insects; flowers contain a little nectar, and have a pleasant odor; very common weeds, visited by honey bees.
POPLAR. (Populus) Aspens. Small purplish flowers, wind-pollinated; pollen abundant, forcibly expelled from the anthers; very valuable in Wisconsin as a pollen plant. Several species found throughout the State.