According to observations of naturalists and beekeepers.
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Field mustard is an upright winter annual or biennial that is a member of the mustard family (Brassicaceae). The oil made from the seed is sometimes also called canola or colza, which is one reason why it is sometimes confused with rapeseed oil.
This species is native to Eurasia, but has spread all over the world and is now naturalized throughout much of North America.
This plant is present in at least 63 states/provinces in this country.
Plants exist as basal rosettes until flowering stems develop at maturity, usually in the second year. Plants grow 1 to 3 (or 4) ft tall from a sometimes fleshy, enlarged taproot, with a many-branched stem. The foliage is generally hairless and sometimes covered with a whitish film. Lower leaves can reach 12 inches long, have a large central lobe, and usually one to four pairs of smaller side lobes. Upper leaves are smaller, non-lobed, and have a pointed tip and widened, clasping base. The bright yellow flowers are clustered at stem tops and have four petals that are 1/4 to 1/2 inch long.
Plants flower from June to August, depending on climate and latitude, and are insect-pollinated and self-incompatible.
Acer glabrum (aka: Rocky Mountain maple, Douglas maple, Greene's maple, New Mexico maple, Torrey maple)
Salix lucida (aka: Shining willow, Greenleaf willow, Tail-leaf willow, Whiplash willow, Pacific willow, Lance-leaf willow, Longleaf willow, Red willow, Western shining willow)
Crataegus douglasii (aka: Black hawthorn, Douglas hawthorn, River hawthorn, Western thornapple)
Populus tremuloides (aka: Quaking aspen, Trembling aspen, Aspen, American aspen, Mountain aspen, Golden aspen, Trembling poplar, White poplar, Popple, Alamo Blanco)
Salix scouleriana (aka: Scouler's willow, Upland willow)
Acer circinatum (aka: Vine maple)
Malus fusca (aka: Oregon crab, Oregon crab apple, Pacific crab apple, Western crab apple)
Rubus spectabilis (aka: Salmonberry)
Salix arbusculoides (aka: Littletree willow)
Salix bebbiana (aka: Bebb willow, Beak willow, Beaked willow, Long-beaked willow, Diamond willow, Chaton, Petit Minou, Smooth Bebb willow)
Malus domestica (aka: Pyrus pumila, Malus pumila, Apple)
Salix planifolia (aka: Diamondleaf willow, Planeleaf willow)
Salix pulchra (aka: Tealeaf willow, Flatleaf willow, Flat-leaved willow, Paneleaf willow, Thin red willow)
Salix hastata (aka: Halberd willow)
Astragalus (aka: Milkvetch, Locoweed, Goat's-thorn)
Salix alaxensis (aka: Feltleaf willow, Alaska willow)
Salix richardsonii (aka: Richardson's willow, Woolly willow)
Allium schoenoprasum (aka: Chives)
Brassica napus (aka: Rapeseed)
Sinapis arvensis (aka: Charlock mustard, California rape, Charlock, Corn mustard, Canola, Kaber mustard, Rapeseed mustard)
Prunus virginiana (aka: Chokecherry, Western chokecherry, Common chokecherry, Black chokecherry)
