According to observations of naturalists and beekeepers.
Where are you?
SOURCE FOR HONEY BEES:
The typical variety of American elm is found throughout eastern North America. Its range extends from southern Newfoundland westward through southern Quebec and Ontario, northwest through Manitoba into eastern Saskatchewan, then south on the upper floodplains and protected slopes of the Dakotas. It is found in the canyons and floodplains of northern and eastern Kansas and in eastern Oklahoma and central Texas. American elm is common along the Gulf Coast and east into central Florida.
American elm can be planted for erosion protection and as a windbreak. Its shallow and wide-spreading roots make it fairly windfirm. American elm is common on wet flats and bottomlands but is not restricted to these sites.
This plant is present in at least 47 states/provinces in this country.
American elm is a deciduous, fast-growing, long-lived tree that may reach 175 to 200 years old with some as old as 300 years. In dense forest stands, American elm may reach 100 to 200 feet (30-36 m) in height and 48 to 60 inches (122-152 cm) in d.b.h. Heights of 80 feet (24 m) are common on medium sites but on very wet or very dry soils, the species is often 40 to 60 feet (12-18 m) tall at maturity. In the forest American elm often develops a clear bole 50 to 60 feet (15-18 m) in length. Open-grown trees fork 10 to 20 feet (3-6 m) from the ground with several erect limbs forming a wide, arching crown.
The alternate, double-toothed leaves are 2 to 5 inches (5-10 cm) long and 1 to 3 inches (2.5-7.5 cm) wide. The dark gray bark is deeply furrowed. The perfect flowers are borne in dense clusters of three or four fascicles. The fruit is a samara consisting of a compressed nutlet surrounded by a membranous wing.
The time of flowering, seed ripening, and seed fall varies by about 100 days between the Gulf Coast and Canada. The flower buds swell early in February in the South and as late as May in Canada. The trees are in flower 2 to 3 weeks before the leaves unfold. The fruit ripens as the leaves unfold or soon afterward. The seed is dispersed as it ripens and seed fall is usually complete by the middle of March in the South and by the middle of June in the North.
Brassica napus (aka: Rapeseed)
Sinapis arvensis (aka: Charlock mustard, California rape, Charlock, Corn mustard, Canola, Kaber mustard, Rapeseed mustard)
Asclepias tuberosa (aka: Butterflyweed, Butterfly Milkweed, Orange Milkweed, Pleurisy Root, Chigger Flower, Canada root, Fluxroot, Indian paintbrush, Indian posy, Orange root, Orange Swallow-wort, Tuber root, Yellow milkweed, White-root, Windroot, Butterfly love)
Agastache foeniculum (aka: Giant hyssop, Blue giant hyssop, Anise hyssop, Fragrant giant hyssop, Lavender giant hyssop)
Borago officinalis (aka: Borage, Starflower, Common borage, Cool-tankard, Tailwort)
Cucumis melo (aka: Cantaloupe, Rockmelon, Sweet melon, Spanspek, Honeydew melon, Honeymelon, Crenshaw, Casaba)
Cirsium arvense (aka: Creeping Thistle, Canada thistle, Field thistle, California thistle, Lettuce from hell thistle, Corn thistle, Cursed thistle, Green thistle, Hard thistle, Perennial thistle, Prickly thistle, Small-flowered thistle, Way thistle, Stinger-needles)
Asteraceae (aka: Aster, Daisy, Composite)