Milkweed Regions & Seed Needs

There are 73 species of native milkweeds in the United States. Many of these species are rare, threatened, and endangered. Monarchs utilize about 30 of these species as host plants with some regularity.

This Fall, Monarch Watch needs seed donations to continue our restoration efforts. Please use the map below to see which milkweed seed is needed in your region. These seeds will be grown and plants will be sold or donated back to their ecoregions. For collection instructions, see our Seed Collecting and Processing page.

Modified from R. G. Bailey, Ecoregions of the United States, USDA Forest Service, revised 1994.

For descriptions, distributions, growing conditions and images of each milkweed species targeted for restoration, please consult the Milkweed Profiles. Directions for milkweed propagation and instructions on how to create monarch habitats can also be found at Growing Milkweeds. Sources of milkweed seeds and plants can be found via our Milkweed Market and the Xerces Society’s Seed Finder.

Those engaged in restoration are urged to consult the county distribution maps and to select species that are previously known to occur. See BONAP’s North American Plant Atlas for Asclepias.

Northeast: Ecoregions 212 (east of Lake Huron), M212, 221 & M221
Seeds needed for all of the Northeast: A. incarnata, A. tuberosa, A. exaltata, A. verticillata, A. viridiflora

A. syriaca is needed for the following states in Ecoregion 221 – MN, MI, WI, KY, TN

The Northeast region extends from the east coast north of the 36th parallel and west to the 100th meridian. This region is the main summer breeding area for monarchs in the eastern United States. The main monarch host plant is Asclepias syriaca (common milkweed). Other species used by monarchs, in order of their abundance and preference, are A. incarnata (swamp milkweed), A. tuberosa (butterflyweed), A. verticillata (whorled milkweed), and A. exaltata (poke milkweed).

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Southeast: Ecoregions M222, 231, M231, 232, 234, & 411
Seeds most needed for the Southeast: A. tuberosa and A. incarnata
Ecoregion 231 – A. syriaca in VA and NC only.
Ecoregion 232– A. humistrata (south of VA only),
Florida 232 – A. perennis and A. verticillata
Ecoregion 234 – A. perennis (Lower Mississippi River valley)

The most widespread and easiest milkweeds to grow in this region are, A. tuberosa (butterflyweed), A. incarnata (swamp milkweed). A. viridis (green antelopehorn) occurs west of the Mississippi. A. verticillata (whorled milkweed) does not grow in the lower Mississippi Valley and is more common in FL and central VA and NC. In the southern portion of the region, A. variegata (white milkweed) is highly sought after for its appearance and behavior. A. perennis (aquatic milkweed) occurs only in hydrated soils. Asclepias humistrata (sandhill/pinewoods milkweed) is recommended for some regions of Florida.

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North Central: Ecoregions 212 (west of Lake Huron), 251, 222 & 332
Seeds most needed for all ecoregions in the North Central Region: A. tuberosa

Ecoregion 222 – A. syriaca, A. sullivantii, A. viridiflora
Ecoregion 251 – A. verticillata, A. viridiflora
Ecoregion 332 – A. syriaca, A. incarnata, A. verticillata

The North Central region contains crucial summer breeding habitat for monarchs in the corn belt. The main monarch host plant in this region is Asclepias syriaca (common milkweed). Other species used by monarchs, in order of their abundance and preference, are A. incarnata (swamp milkweed), A. tuberosa (butterflyweed), and A. verticillata (whorled milkweed).

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South Central: Ecoregions 255, 315 & 311

Seeds most needed for all ecoregions in the South Central region: A. tuberosa, A. oenotheroides, A viridis and A. asperula

The South Central region includes both Texas and Oklahoma. The main monarch host plants in this region are A. viridis (green antelope horn milkweed), A. asperula (antelope horn/spider milkweed) and A. oenotheroides (Zizotes milkweed).

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The West (exclusive of the Desert Southwest and West Coast): Ecoregions 331, 332, 341, 342
Seeds most needed for all of the West are: A. speciosa.

A. tuberosa is needed where it naturally occurs. See the North America Plant Atlas for distribution.

The west region covers all the area west of the 100th meridian except west Texas, AZ, NM and the west coast. Asclepias speciosa (showy milkweed) occurs in all the western states and is the top choice for restoration in all states except AZ, where other native species appear to be more abundant and preferred by monarchs. A. fascicularis (Mexican whorled/narrowleaf milkweed) is the second choice in the west and could be used in California, Nevada and SW Oregon.

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The Desert Southwest: Ecoregions 313, M313, 321 & 322
Seeds most needed in the Arizona/New Mexico region are: A. angustifolia, A. subulata, and A. asperula

Ecoregion 321 – A. oenotheroides.

A. tuberosa is needed only where it naturally occurs. See the BONAP North American Plant Atlas for distribution.

The environment of Arizona and New Mexico is extremely dry and has a number of unique milkweed species. Many of these species can probably be utilized in dry gardens (xeriscapes). Based on the preferences by monarchs and their potential for restoration, we recommend the collecting of seeds and propagation of A. angustifolia (Arizona milkweed), A. subulata (rush milkweed), A. asperula (antelope horn/spider milkweed), and A. tuberosa (butterflyweed, the yellow flowered western biotype).

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The West Coast: Ecoregions 242, M242, 261, M261, 262, M262, 263
Seeds most needed on the West Coast are: A. fascicularis and A. speciosa.
CA – A. erosa, A. californica, A. cordifolia, A. eriocarpa, and A. vestita.

The two milkweed species most easily used for restoration and introduction into gardens in California, Washington and Oregon are A. fascicularis (Mexican whorled/narrowleaf milkweed) and A. speciosa (showy milkweed).

A number of additional species are also used by monarchs exclusively in California and are relatively easy to bring into gardens and have potential for use in restoration projects. Each species has a unique distribution within California and restoration efforts should target counties in which these species are known to occur. Other species include A. erosa (desert milkweed), A. californica (California milkweed), A. cordifolia (heartleaf milkweed), A. eriocarpa (woolypod milkweed), and A. vestita (woolly milkweed).

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