According to observations of naturalists and beekeepers.
Where are you?
Native to Eurasia, Russian-thistle is distributed throughout most arid and semiarid regions of the world. In North America, Russian thistle occurs from British Columbia east to Labrador and south through the conterminous United States to northern Mexico. It is most common in central and western regions of Canada and the United States, and along the Atlantic and Gulf coasts. Limited southern and eastern inland populations occur along with waste areas and railroad tracks. Russian-thistle is adventitious in Hawaii.
This plant is present in at least 32 states/provinces in this country.
Russian-thistle is an exotic, annual, erect, xerohalophytic forb. It is highly branched and rounded in form, growing from 1 to 3 feet (0.3-1 m) in height and from 1 to 5 feet (0.3-1.5 m) in diameter. The awl-shaped, spiny-tipped leaves bear small, inconspicuous flowers in the leaf axils. The small, winged seed, retained in the leaf axils until after plant death, contains no endosperm tissue but is instead comprised of a spirally-coiled, complete embryo already containing some chlorophyll. The root system consists of a taproot, reaching 0.3 foot (1 m) or more in-depth, and extensive lateral roots. Under crowded conditions, roots are shallow.
The following seasonal development has been reported for Russian-thistle: germinates: late April - August, flowers: June - August, seeds mature: August - November, plant dies: first fall frost, seeds disseminate: late fall.
Malus fusca (aka: Oregon crab, Oregon crab apple, Pacific crab apple, Western crab apple)
Salix bebbiana (aka: Bebb willow, Beak willow, Beaked willow, Long-beaked willow, Diamond willow, Chaton, Petit Minou, Smooth Bebb willow)
Rhamnus cathartica (aka: Common buckthorn, European buckthorn, Dahurian buckthorn)
Rubus laciniatus (aka: Cutleaf blackberry, Evergreen blackberry, Slashed blackberry)
Rhus glabra (aka: Smooth sumac, Common sumac, Rocky Mountain sumac, Red sumac, Western sumac, White sumac)
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)
Calendula officinalis (aka: Marigold, Calendula, Pot marigold, English marigold)
Salix brachycarpa (aka: Shortfruit willow, Barren-ground willow, Small-fruit sand dune willow, Small-fruit willow)
Rubus idaeus (aka: Raspberry, Black-haired red raspberry, Brilliant red raspberry, American red raspberry, Red raspberry, Smoothleaf red raspberry, Wild raspberry, Wild red raspberry, Grayleaf raspberry)
Rubus parviflorus (aka: Thimbleberry, Western thimbleberry)
Amorpha fruticosa (aka: Desert false indigo, False indigo-bush, Bastard indigobush, Indigo Bush)
Brassica rapa (aka: Field mustard, Common mustard, Wild mustard, Wild turnip, Forage turnip, Wild rutabaga, Birdsrape mustard, Rape mustard)
Salix planifolia (aka: Diamondleaf willow, Planeleaf willow)
Rubus armeniacus (aka: Himalayan blackberry, Rubus discolor, Rubus procerus)
Salsola kali (aka: Russian thistle, Tumbleweed, Prickly saltwort)
Cucumis melo (aka: Cantaloupe, Rockmelon, Sweet melon, Spanspek, Honeydew melon, Honeymelon, Crenshaw, Casaba)
Citrullus lanatus (aka: Watermelon)
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)
Borago officinalis (aka: Borage, Starflower, Common borage, Cool-tankard, Tailwort)
Cephalanthus occidentalis (aka: Common buttonbush, Buttonball, Buttonbush, Button willow, Riverbush, Honey-bells)
