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 bebbiana (aka: Bebb willow, Beak willow, Beaked willow, Long-beaked willow, Diamond willow, Chaton, Petit Minou, Smooth Bebb 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)
Rhus glabra (aka: Smooth sumac, Common sumac, Rocky Mountain sumac, Red sumac, Western sumac, White sumac)
Brassica napus (aka: Rapeseed)
Allium schoenoprasum (aka: Chives)
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)
Tilia americana (aka: American basswood, Basswood, Linden)
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)
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)
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)
Agastache foeniculum (aka: Giant hyssop, Blue giant hyssop, Anise hyssop, Fragrant giant hyssop, Lavender giant hyssop)
Cucumis sativus (aka: Cucumber, Cetriolo, Gherkin)
Citrullus lanatus (aka: Watermelon)
Borago officinalis (aka: Borage, Starflower, Common borage, Cool-tankard, Tailwort)
Diervilla lonicera (aka: Northern bush honeysuckle, Bush-honeysuckle, Dwarf bush-honeysuckle, Herbe bleue)
Cephalanthus occidentalis (aka: Common buttonbush, Buttonball, Buttonbush, Button willow, Riverbush, Honey-bells)
Hyssopus officinalis (aka: Hyssop)
Calluna vulgaris (aka: Heather, Scotch heather, Common heather, Ling, Simply heather)