According to observations of naturalists and beekeepers.
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Calendula (Calendula officinalis, Asteraceae) is one of the easiest herbs to grow and a highly versatile medicinal plant - naturally, it finds its way into the hearts and gardens of all herb lovers. They are native to southwestern Asia, western Europe, Macaronesia, and the Mediterranean.
Popular herbal and cosmetic products named 'calendula' invariably derive from C. Officinalis. Calendula species have been used traditionally as culinary and medicinal herbs. The petals are edible and can be used fresh in salads or dried and used to color cheese or as a replacement for saffron.
This plant is present in at least 15 states/provinces in this country.
Depending on variety and culture, the plants grow 30.5-76.2 cm in height and about as wide. The leaves are bright green and typically about 10.2 cm long. The lower leaves are oval with a rounded tip (spatulate) and upper leaves are lance-shaped with pointed tips.
The flowers are typically 5.1-7.6 cm in diameter and held on thick sturdy stems. Calendulas are single or double-flowered and come in a range of colors from cream to light yellow to electric yellow to orange. Some have dark brown centers and all are beautiful.
Regular pinching keeps the 30-90 cm plant bushy and prevents tall, spindly stalks.
If deadheaded regularly, this plant can bloom from spring through fall and beyond. In warmer areas, the calendula may take a break from blooming during summer heat and then put on a show as temperatures fall in autumn.
Salix lucida (aka: Shining willow, Greenleaf willow, Tail-leaf willow, Whiplash willow, Pacific willow, Lance-leaf willow, Longleaf willow, Red willow, Western shining willow)
Prunus pumila (aka: Sandcherry, Western sandcherry, Eastern sandcherry, Great Lakes sandcherry)
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)
Acer platanoides (aka: Norway maple)
Prunus americana (aka: American plum, Goose plum, River plum, Wild plum)
Vaccinium angustifolium (aka: Lowbush blueberry, Early low-bush blueberry, Low sweet blueberry)
Rubus canadensis (aka: Smooth blackberry, Thornless blackberry, Canadian blackberry, Smooth highbush blackberry)
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)
Robinia pseudoacacia (aka: Black locust, False acacia, Yellow locust, White locust, Green locust, Post locust, Falsa acacia, Robinia)
Catalpa speciosa (aka: Northern catalpa, Hardy catalpa, Western catalpa, Cigar tree, Catawba-tree, Bois chavanon)
Acer pensylvanicum (aka: Striped maple, Moosewood, Goosefoot maple, Whistlewood)
Acer spicatum (aka: Mountain maple, Low maple, Moose maple, Water maple, Plaine batarde, Fouereux)
Astragalus (aka: Milkvetch, Locoweed, Goat's-thorn)
Salix nigra (aka: Black willow, Swamp willow, Southwestern black willow, Gulf black willow, Scythe-leaved willow)
Salix planifolia (aka: Diamondleaf willow, Planeleaf willow)
Ajuga reptans (aka: Bugle, Blue bugle, Bugleherb, Bugleweed, Carpetweed, Carpet bugleweed, Common bugle, St. Lawrence plant)
Salix alaxensis (aka: Feltleaf willow, Alaska willow)
Rhus glabra (aka: Smooth sumac, Common sumac, Rocky Mountain sumac, Red sumac, Western sumac, White sumac)
Allium schoenoprasum (aka: Chives)
Brassica napus (aka: Rapeseed)
Sinapis arvensis (aka: Charlock mustard, California rape, Charlock, Corn mustard, Canola, Kaber mustard, Rapeseed mustard)
Aronia melanocarpa (aka: Black chokeberry, Rowan, Mountain Ash, Sorbus)
Prunus pensylvanica (aka: Pin cherry, Fire cherry, Bird cherry)
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)
Prunus serotina (aka: Black cherry, Wild black cherry, Rum cherry, Mountain black cherry, Wild cherry)
Rhamnus cathartica (aka: Common buckthorn, European buckthorn, Dahurian buckthorn)
Vaccinium corymbosum (aka: Highbush blueberry, High-bush blueberry, Northern highbush blueberry, Tall blueberry, Rabbiteye blueberry, Blue huckleberry, Tall huckleberry, Swamp huckleberry, High blueberry, Swamp blueberry)
Salix glauca (aka: Grayleaf willow, Gray willow, Gray-leaved willow)
Tilia americana (aka: American basswood, Basswood, Linden)
Salix brachycarpa (aka: Shortfruit willow, Barren-ground willow, Small-fruit sand dune willow, Small-fruit willow)
Amorpha fruticosa (aka: Desert false indigo, False indigo-bush, Bastard indigobush, Indigo Bush)
Asclepias syriaca (aka: Сommon milkweed, Butterfly flower, Silkweed, Silky swallow-wort, Virginia silkweed)
Salsola kali (aka: Russian thistle, Tumbleweed, Prickly saltwort)
Brassica rapa (aka: Field mustard, Common mustard, Wild mustard, Wild turnip, Forage turnip, Wild rutabaga, Birdsrape mustard, Rape mustard)
Echium vulgare (aka: Viper's bugloss, Blueweed, Blue thistle)
Cucumis sativus (aka: Cucumber, Cetriolo, Gherkin)
Agastache foeniculum (aka: Giant hyssop, Blue giant hyssop, Anise hyssop, Fragrant giant hyssop, Lavender giant hyssop)
Chamaenerion angustifolium (aka: Fireweed, Great willowherb, Rosebay willowherb, Saint Anthony's Laurel, French-willow)
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)
Cucumis melo (aka: Cantaloupe, Rockmelon, Sweet melon, Spanspek, Honeydew melon, Honeymelon, Crenshaw, Casaba)
Prunus virginiana (aka: Chokecherry, Western chokecherry, Common chokecherry, Black chokecherry)
Diervilla lonicera (aka: Northern bush honeysuckle, Bush-honeysuckle, Dwarf bush-honeysuckle, Herbe bleue)
Rubus chamaemorus (aka: Cloudberry, Bake apple, Baked apple berry, Bakeapple, Nordic berry, Knotberry, Aqpik, Low-bush salmonberry, Averin, Evron)