Asclepias incarnata

Life-forms

Classification System: APG IV

Superregnum: Eukaryota
Regnum: Plantae
Cladus: Angiosperms
Cladus: Eudicots
Cladus: Core eudicots
Cladus: Asterids
Cladus: Lamiids
Ordo: Gentianales

Familia: Apocynaceae
Subfamilia: Asclepiadoideae
Tribus: Asclepiadeae
Subtribus: Asclepiadinae
Genus: Asclepias
Species: Asclepias incarnata
Subspecies: A. i. subsp. incarnata – A. i. subsp. pulchra
Name

Asclepias incarnata L. (1753)
Synonyms

Homotypic
Acerates incarnata (L.) Decne. in A.P.de Candolle, Prodr. 8: 523 (1844).

References

Linnaeus, C. 1753. Species Plantarum. Tomus I: 215. Reference page.

Links

Hassler, M. 2018. Asclepias incarnata. World Plants: Synonymic Checklists of the Vascular Plants of the World In: Roskovh, Y., Abucay, L., Orrell, T., Nicolson, D., Bailly, N., Kirk, P., Bourgoin, T., DeWalt, R.E., Decock, W., De Wever, A., Nieukerken, E. van, Zarucchi, J. & Penev, L., eds. 2018. Species 2000 & ITIS Catalogue of Life. Published on the internet. Accessed: 2018 Sep 28. Reference page.
Govaerts, R. et al. 2018. Asclepias incarnata in World Checklist of Selected Plant Families. The Board of Trustees of the Royal Botanic Gardens, Kew. Published on the internet. Accessed: 2018 Sep 28. Reference page.
International Plant Names Index. 2018. Asclepias incarnata. Published online. Accessed: Sep 28 2018.
The Plant List 2013. Asclepias incarnata in The Plant List Version 1.1. Published on the internet. Accessed: 2018 Sep 28.
Tropicos.org 2018. Asclepias incarnata. Missouri Botanical Garden. Published on the internet. Accessed: 2018 Sep 28.
USDA, ARS, Germplasm Resources Information Network. Asclepias incarnata in the Germplasm Resources Information Network (GRIN), U.S. Department of Agriculture Agricultural Research Service. Accessed: 07-Oct-06.
USDA, NRCS (2006). The PLANTS Database, 6 March 2006 (http://plants.usda.gov).Data compiled from various sources by Mark W. Skinner. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Vernacular names
Boarisch: Sumf-Seinpflaunzen
Deutsch: Sumpf-Seidenpflanze
English: swamp milkweed
suomi: Purppurasilkkiyrtti
русский: Ваточник мясо-красный
svenska: Rosensidenört

Asclepias incarnata, the swamp milkweed, rose milkweed, rose milkflower, swamp silkweed, or white Indian hemp, is a herbaceous perennial plant species native to North America.[3] It grows in damp through wet soils and also is cultivated as a garden plant for its flowers, which attract butterflies and other pollinators with nectar. Like most other milkweeds, it has latex containing toxic chemicals,[4] a characteristic that repels insects and other herbivorous animals.

Description

Swamp milkweed is an upright, 100 to 150 cm (39 to 59 in) tall plant, growing from thick, fleshy, white roots. Typically, its stems are branched and the clump forming plants emerge in late spring after most other plants have begun growth for the year. The oppositely arranged leaves are 7.5 to 15 cm (3 to 6 in) long and 1 to 4 cm (1⁄2 to 1+1⁄2 in) wide and are narrow and lance-shaped, with the ends tapering to a sharp point.[5]

The plants bloom in early through mid-summer, producing small, fragrant, pink to mauve (sometimes white) colored flowers in rounded umbellate racemes. The flower color varies from darker shades of purple through soft, pinkish purple and a white flowering form exists as well. The actinomorphic flowers have five reflexed petals and an elevated central crown. After blooming, green follicles, approximately 12 cm (4+3⁄4 in) long, are produced that when ripe, split open. They then release light or dark brown, flat seeds that are attached to silver-white, silky hairs which catch the wind. This natural mechanism for seed dispersal is similar to that used by other milkweed species.[6]
Taxonomy

As of July 2021, Kew's Plants of the World Online (POWO) accepts 2 infraspecies,[2] each having numerous synonyms:[7][8]

Asclepias incarnata subsp. incarnata
Synonym: Asclepias albiflora Raf.
Synonym: Asclepias amoena Brongn.
Synonym: Asclepias incarnata f. albiflora (Raf.) A.Heller
Synonym: Asclepias incarnata f. candida Fernald
Synonym: Asclepias incarnata var. glabra Eaton & Wright
Synonym: Asclepias incarnata f. rosea B.Boivin
Synonym: Asclepias maritima Raf. ex Decne.
Synonym: Asclepias verecunda Salisb.
Asclepias incarnata subsp. pulchra (Ehrh. ex Willd.) Woodson
Synonym: Asclepias incarnata var. neoscotica Fernald
Synonym: Asclepias incarnata f. pulchra (Ehrh. ex Willd.) Voss
Synonym: Asclepias incarnata var. pulchra (Ehrh. ex Willd.) Pers.
Synonym: Asclepias pulchra Ehrh. ex Willd.
Synonym: Asclepias pulchra f. albiflora House

The flower stalks and abaxial leaf surfaces of subspecies pulchra are abundantly pubescent, whereas those of the autonymous subspecies are nearly glabrous.[9]
Habitat

Swamp milkweed prefers moisture retentive through damp soils in full sun or partial shade and is typically found growing wild near the edges of ponds, lakes, streams, and low areas—or along ditches.[10] It is one of the best attractors of the monarch butterfly (Danaus plexippus), which feeds on the flowers and lays eggs on the plants.[11] The emerging caterpillars feed on the leaves.

The plants have specialized roots which function in heavy, wet soils. The scented, thick, white roots are in environments low in oxygen. Blooming occurs in mid- through late summer and after blooming long, relatively thin, rounded follicles are produced that grow uprightly. They split open in late summer through late fall, releasing seeds attached to silky hairs, which act as parachutes that carry the seeds in wind currents.
Cultivation

A. incarnata is cultivated frequently, and a number of cultivars are available. They are used especially in gardens designed to attract butterflies (see Butterfly gardening). The nectar of the plant attracts many other species of insect as well. The plants are also sold as freshly cut flowers, mostly for their long-lasting flower display, but sometimes, for the distinctive follicles.

Monarch Watch provides information on rearing monarchs and their host plants.[12] Efforts to increase monarch butterfly populations by establishing butterfly gardens and monarch migratory "waystations" require particular attention to the target species' food preferences and population cycles, as well to the conditions needed to propagate and maintain their food plants.[13]

The seeds of some milkweeds need periods of cold treatment (cold stratification) before they will germinate.[14] To protect seeds from washing away during heavy rains and from seed–eating birds, one can cover the seeds with a light fabric or with an 0.5 in (13 mm) layer of straw mulch.[15] However, mulch acts as an insulator. Thicker layers of mulch can prevent seeds from germinating if they prevent soil temperatures from rising enough when winter ends. Further, few seedlings can push through a thick layer of mulch.[16]

Breeding monarchs prefer to lay eggs on A. incarnata.[17] The species is therefore often planted in butterfly gardens and "Monarch Waystations" to help sustain monarch butterfly populations.[18][19] However, A. incarnata is an early successional plant that usually grows at the margins of wetlands and in seasonally flooded areas.[20]

The plant is slow to spread via seeds, does not spread by runners and tends to disappear as vegetative densities increase and habitats dry out. Although A. incarnata plants can survive for up to 20 years, most live only two-five years in gardens. The species is not shade-tolerant and is not a good vegetative competitor.[20]

References

Maiz-Tome, L. (2016). "Asclepias incarnata". The IUCN Red List of Threatened Species. IUCN. 208. e.T64264155A67728543. doi:10.2305/IUCN.UK.2016-1.RLTS.T64264155A67728543.en.
"Asclepias incarnata L.". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 1 July 2021.
(1) USDA, NRCS (n.d.). "Asclepias incarnata". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team.
(2) Kirk, S.; Belt, S. "Plant fact sheet for swamp milkweed (Asclepias incarnata)" (PDF). Beltsville, Maryland: United States Department of Agriculture: Natural Resources Conservation Service: Norman A. Berg National Plant Materials Center. Archived (PDF) from the original on July 9, 2021. Retrieved July 9, 2021.
(3) Holmes, Forest Russell. "Swamp Milkweed (Asclepias incarnata L.)". Plant of the Week. Washington, D.C.: United States Department of Agriculture: United States Forest Service. Archived from the original on March 28, 2021. Retrieved July 9, 2021.
Foster, S. and R. A. Caras. (1994). A Field Guide to Venomous Animals and Poisonous Plants, North America, North of Mexico. Boston: Houghton Mifflin. p. 122. ISBN 978-0-395-93608-5.
Dickinson, T.; Metsger, D.; Bull, J.; Dickinson, R. (2004). The ROM Field Guide to Wildflowers of Ontario. Toronto: Royal Ontario Museum. p. 136. ISBN 0771076525. OCLC 54691765.
"Swamp Milkweed (Asclepias incarnata)". Northern Prairie Wildlife Research Center. USGS. August 3, 2006. Archived from the original on 13 May 2009. Retrieved March 30, 2009.
"Asclepias incarnata subsp. incarnata". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 1 July 2021.
"Asclepias incarnata subsp. pulchra (Ehrh. ex Willd.) Woodson". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 1 July 2021.
Gilman, Arthur V. (2015). New Flora of Vermont. Memoirs of The New York Botanical Garden, Volume 110. Bronx, New York, USA: The New York Botanical Garden Press. ISBN 978-0-89327-516-7.
"Asclepias incarnata". Kemper Center for Home Gardening. Missouri Botanical Garden. Archived from the original on 1 April 2009. Retrieved March 30, 2009.
Pocius, Victoria M.; Debinski, Diane M.; Pleasants, John M.; Bidne, Keith G.; Hellmich, Richard L. (January 8, 2018). "Monarch butterflies do not place all of their eggs in one basket: oviposition on nine Midwestern milkweed species". Ecosphere. Ecological Society of America (ESA). 9 (1): 1–13. doi:10.1002/ecs2.2064. Retrieved July 6, 2021 – via Wiley Online Library.
"Monarch Watch". monarchwatch.org. Retrieved September 27, 2015.
(1) Borders, Brianna; Lee–Mäder, Eric (2014). "Milkweed Propagation and Seed Production" (PDF). Milkweeds: A Conservation Practitioner's Guide: Plant Ecology, Seed Production Methods, and Habitat Restoration Opportunities. Portland, Oregon: The Xerces Society for Invertebrate Conservation. pp. 21–95. Archived (PDF) from the original on July 4, 2021. Retrieved July 12, 2021.
(2) Landis, Thomas D.; Dumroese, R. Kasten (2015). "Propagating Native Milkweeds for Restoring Monarch Butterfly Habitat" (PDF). International Plant Propagators' Society, Combined Proceedings (2014). 64: 299–307. Archived (PDF) from the original on March 8, 2021. Retrieved July 11, 2021 – via United States Department of Agriculture: United States Forest Service.
(1) Borders, Brianna; Lee–Mäder, Eric (2014). "Milkweed Propagation and Seed Production: Stratification" (PDF). Milkweeds: A Conservation Practitioner's Guide: Plant Ecology, Seed Production Methods, and Habitat Restoration Opportunities. Portland, Oregon: The Xerces Society for Invertebrate Conservation. pp. 28–29. Archived (PDF) from the original on July 4, 2021. Retrieved July 12, 2021.
(2) Landis, Thomas D.; Dumroese, R. Kasten (2015). "Propagating Native Milkweeds for Restoring Monarch Butterfly Habitat" (PDF). International Plant Propagators' Society, Combined Proceedings (2014). 64: 302. Archived (PDF) from the original on March 8, 2021. Retrieved July 11, 2021 – via United States Department of Agriculture: United States Forest Service. "Many sources of milkweed seeds require stratification (cold, moist treatment) before sowing. In a review of stratification requirements for common milkweed, recommendations varied from as short as 7 days to as long as 11 months at 5°C (41°F) (Luna and Dumroese, 2013). Butterfly milkweed (A. tuberosa) germination increased from 29 to 48 to 62% as stratification duration increased from 0 to 30 to 60 days, respectively (Bir, 1986). Our informal natural stratification trial with showy (milkweed) and narrow leaf milkweed (A. fascicularis) in southern Oregon revealed that seeds began to germinate after 15 weeks in stratification (Fig. 3A)."
(3) Higgins, Adrian (27 May 2015). "7 milkweed varieties and where to find them". Home & Garden. The Washington Post. Archived from the original on 26 September 2020. Retrieved 17 October 2020. "Seed may be stubborn to germinate and may need a period of cold treatment.".
(1) Mader, Eric; Shepherd, Mathew; Vaughan, Mace; Black, Scott Hoffman; LeBuhn, Gretchen (2011). Estabishing Pollinator Habitat from Seed: Sowing Seed. Attracting Native Pollinators: Protecting North America's Bees and Butterflies: The Xerces Society guide. North Adams, Massachusetts: Storey Publishing. pp. 113–114. ISBN 9781603427470. LCCN 2010043054. OCLC 776997073. Retrieved July 7, 2021 – via Internet Archive.
(2) Landis, Thomas D.; Dumroese, R. Kasten (2015). "Propagating Native Milkweeds for Restoring Monarch Butterfly Habitat: Propagating Native Milkweeds: Seed Propagation" (PDF). International Plant Propagators' Society, Combined Proceedings (2014). 64: 302. Archived (PDF) from the original on March 8, 2021. Retrieved July 11, 2021 – via United States Department of Agriculture: United States Forest Service. "Any of the standard seed propagation methods (Landis et al., 1999) are effective with milkweed. Direct sowing of non-stratified seeds during the fall followed by exposure to ambient winter conditions can be effective, but the seeds must be mulched and protected. Cover sown seeds with a thin mulch; research has found that common milkweed seeds germinated better when planted 1 to 2 cm (0.4 to 0.8 in.) deep than when at the soil surface (Jeffery and Robison, 1971)."
Bush-Brown, James; Bush-Brown, Louise (1958). "Chapter 32: Mulches". America's garden book. New York: Charles Scribner's Sons. p. 768. LCCN 58005738. OCLC 597041748 – via Internet Archive.
Pocius, Victoria M.; Debinski, Diane M.; Pleasants, John M.; Bidne, Keith G.; Hellmich, Richard L. (January 8, 2018). "Monarch butterflies do not place all of their eggs in one basket: oviposition on nine Midwestern milkweed species". Ecosphere. Ecological Society of America (ESA). 9 (1): 1–13. doi:10.1002/ecs2.2064. Retrieved July 6, 2021 – via Wiley Online Library.
(1) "Asclepias incarnata". North Carolina Extension Gardener Plant Toolbox. Raleigh, North Carolina: North Carolina State University: N.C. Cooperative Extension. Archived from the original on November 28, 2020. "Use in a naturalized area, pollinator garden or along a pond or stream in full sun to partial shade."
(2) "Asclepias incarnata". St. Louis, Missouri: Missouri Botanical Garden. Archived from the original on February 25, 2021. Retrieved July 5, 2021. "Uses: Sunny borders, stream/pond banks, butterfly gardens."
(3) Gomez, Tony. "Asclepias Incarnata: Swamp Milkweed for Monarch Butterflies and Caterpillars". Monarch Butterfly Garden. Archived from the original on April 22, 2021. Retrieved July 5, 2021.
(4) Vogt, Benjamin (February 19, 2015). "Great Design Plant: Asclepias Incarnata for a Butterfly Garden: Beautiful swamp milkweed makes it easy to help monarchs and other pollinators in eastern U.S. gardens". Palo Alto, California: Houzz. Archived from the original on May 7, 2021. Retrieved July 5, 2021.
Abugattas, Alonzo (3 January 2017). "Monarch Way Stations". Capital Naturalist. Archived from the original on 8 March 2021. Retrieved 5 July 2021 – via Blogger. "A better option for most gardeners might be Swamp Milkweed (A. incarnata) which, despite its name, does fine in regular garden soil and doesn’t spread by runners."
"Asclepias incarnata". Bring Back The Monarchs. Monarch Watch. Archived from the original on June 12, 2021. Retrieved July 5, 2021. "Life span: In gardens most plants live two-five years but known to survive up to 20 years. .... Propagation: Slow to spread via seeds. .... 'Overhead Conditions: Not shade tolerant. An early successional plant that tends to grow at the margins of wetlands and in seasonally flooded areas. It is not a good vegetative competitor and tends to disappear as vegetative density increases and habitats dry out."