Danaus plexippus, the monarch, can be found in Hawaii and in every state in the continental US.


Favored nectar plants -- those with 10 or more observations, a compression of 234 genera contained in 1,840 entries -- are arranged here in descending order: Cirsium (Thistle), Lantana, Verbena, Bidens, Asclepias, Salvia, Zinnia, Solidago, Conoclinium, Buddleja, Helianthus, Eupatorium, Symphyotrichum, Liatris, Echinacea, Trifolium, Taraxacum (Dandelion), Pentas, Carduus (Thistle), Verbesina, Tithonia, Coreopsis, Dahlia, Baccharis, Echium, Gaillardia, Allium, Rudbeckia, Ageratum, Cosmos, Tagetes, Phlox, Pseudogynoxys, Eutrochium, Daucus, Cephalanthus, Scabiosa, and Monarda.


USDA Growing Zones for these plants include: 2,3,4,5,6,7,8,9,10,11

If you live in the US you are very likely in a position to create a monarch habitat. A viable habitat consists of a 50% milkweed plants (Asclepias) and 50% nectar plants. As few as six plants creates a habitat -- three milkweeds and three nectar plants. Or course, the more the better for monarchs. They will use, and need, urban, suburban, and rural garden habitats during each stage of their migration.

Go to your favorite local nursery with this plant list -- and ask for GMO-free nectar and host plants for your habitat. For native plants in your zip code: https://nativeplantfinder.nwf.org/

Midwest and Eastern Population
If you live in any of the Midwest's five states that make up the Southern Great Plains, than planting fall flowering habitats are needed now, as it is an opportunity for migrating adults Monarchs to create another generation that will then head to the overwintering sites in Mexico.*

*Citation: Midwest Association of Fish and Wildlife Agencies. 2023

Many Asclepias retain their biomass into the fall, making them a potential fall host plant. While it may be an incomplete list, these milkweed were suggested as fall flowering in each of the five states:
Texas: Asclepias tuberosa (Butterfly Milkweed), Asclepias linearis (Slim Milkweed), and Asclepias oenotheroides (Zizotes Milkweed)

Oklahoma: Asclepias verticillata (Whorled Milkweed)
Kansas: Asclepias verticillata (Whorled Milkweed), Asclepias syriaca (Common Milkweed)
Missouri: Asclepias verticillata (Whorled Milkweed), Asclepias syriaca (Common Milkweed), Asclepias tuberosa (Butterfly Milkweed), and Asclepias incarnata (Swamp Milkweed)
Arkansas: Asclepias verticillata (Whorled Milkweed),White Milkweed (Asclepias variegata)

It is worth noting, that a study of Asclepias* conducted in Iowa revealed that Asclepias speciosa, sullivantii, syriaca, and tuberosa produced the best larval survival results, with A. syriaca performing the best overall.
*https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2018.00169/full

If you live in a state east of the Rocky Mountains, and in the Great Plains, your habitat will likely attract Monarchs for breeding. Three to four generations are created during their breeding season in all these states. As few as six plants in an urban, suburban, or rural garden may attract monarchs -- three milkweeds and three nectar plants.
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If you live in California, you are very likely in a position to create a monarch habitat. A viable monarch habitat consists of a 50% milkweed plants (Asclepias) and 50% nectar plants. As few as 6 plants will attract monarch's to feed. They will use habitats during each stage of their migration. The Western migrating population is in serious decline and may, or may not, recover (for information go to https://onlinelibrary.wiley.com/doi/10.1111/ele.13816). Providing viable habitat in suburban, urban, and rural gardens may aid in their recovery -- either contributing to a permanent localized population or an uncertain contribution to the recovery of the migrating population. Either way? Put plants in the ground.

Spring Habitat: Monarchs will migrate through Santa Cruz, San Mateo, Santa Clara, Monterey, San Benito, and parts of San Luis Obispo Counties seeking habitat for creating the first generation of butterflies. In southern CA they will migrate inland from the coast in Santa Barbara, Ventura, and LA Counties. This is an important stage in their development.
Providing Monarch habitat suitable to support the spring migration sets the stage for the development of a larger population.
Caterpillars raised early add to that year's population growth throughout that season -- each insect producing 3-4 more generations of Monarchs.

Fall Habitat: The last generation of Monarchs in California is typically created in inland areas during late summer to early fall.
This area includes counties in the Central Valley (e.g. Sacramento, San Joaquin, and Stanislaus),
as well as parts of the Sierra Nevada foothills and other inland regions where milkweed is still available.
The Sierra Nevada foothills include: Placer County, El Dorado County, Amador County, Calaveras County, Tuolumne County, Mariposa County, Madera County,
Fresno County, Tulare County, Nevada County, and Yuba County.

Habitats between migrations: During the summer months Monarchs can be found in many counties across California.
Central Valley counties: Sacramento, San Joaquin, Stanislaus, Merced, Fresno, Kings, Tulare, Kern.
Sierra Nevada foothills counties: Placer, El Dorado, Amador, Calaveras, Tuolumne, Mariposa, Madera.
Coastal and near-coastal counties: Humboldt, Mendocino, Sonoma, Marin, San Francisco, San Mateo, Santa Cruz, Monterey, San Luis Obispo, Santa Barbara, Ventura,
Los Angeles, Orange, San Diego.
Inland counties: Shasta, Tehama, Butte, Yuba, Sutter, Yolo, Solano, Contra Costa, Alameda, Santa Clara.
Southern California inland counties: Riverside, San Bernardino, Imperial

If you live in Northwest, you are very likely in a position to create a summer-breeding Monarch habitat with as few as six plants. 
Key areas where Monarchs are found include: 
Oregon: Willamette Valley (Lane, Linn, Benton, Polk, Marion, Yamhill counties), Columbia River Gorge area (Hood River, Wasco counties), and 
Southern Oregon (Jackson, Josephine counties) 
Washington: Eastern Washington (Klickitat, Yakima, Benton, Walla Walla counties) and Puget Sound region (King, Pierce, Thurston counties) 
Idaho: Southwestern Idaho (Ada, Canyon, Owyhee counties), and North-central Idaho (Nez Perce, Latah counties)

Milkweed Host plants:
Asclepias (DO NOT plant A. curavassica, it is harmful to Monarchs)
Asclepias amplexicaulis
Asclepias asperula
Asclepias californica
Asclepias cancellata
Asclepias cordifolia
Asclepias curtissii
Asclepias eriocarpa
Asclepias erosa
Asclepias exaltata
Asclepias fascicularis
Asclepias hirtella
Asclepias humistrata
Asclepias incarnata
Asclepias lanceolata
Asclepias longifolia
Asclepias nivea
Asclepias obovata
Asclepias oenotheroides
Asclepias physocarpa
Asclepias purpurascens
Asclepias semilunata
Asclepias speciosa
Asclepias subulata
Asclepias subverticillata
Asclepias sullivantii
Asclepias syriaca
Asclepias tomentosa
Asclepias tuberosa rolfsii
Asclepias variegata
Asclepias verticillata
Asclepias vestita
Asclepias viridiflora
Asclepias viridis

PD image courtesy of:
Perlick Laure, USFWS

CC0 images courtesy of
Lila
Zygy