Asclepias incarnata, swamp milkweed
Pavek, Diane S. 1992. Asclepias incarnata, swamp milkweed. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-reviews/ascinc
| Abbreviation | Common Name | Scientific Name | Classification | Status |
|---|---|---|---|---|
| Plants | ||||
| ASCINC | swamp milkweed | Asclepias incarnata | Life Form: Plants/Forb Kingdom: Plantae Class: Dicot Order: Gentianales Family: Asclepidaceae Genus: Asclepias | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
Taxonomy
The currently accepted scientific name of swamp milkweed is Asclepias incarnata L. (Asclepidaceae). There is disagreement in the taxonomic literature about infrataxa treatment. Two subspecies are recognized:
- Asclepias incarnata ssp. incarnata [23]
- A. i. ssp. pulchra (Ehrh. ex Willd.) Woods. [23]
Also recognized are the following variety and forms:
- A. i. var. incarnata f. incarnata [21]
- A. i. var. incarnata f. albiflora—Found only in Missouri [21]
- A. i. var. incarnata f. rosea Bowin—Found only in southern Ontario, Canada [18].
This report does not use infrataxa; they rarely appear in the literature.
Synonyms
- Asclepias pulchra Ehrh. ex Willd.
Other Common Names
milkweed
General Distribution
Swamp milkweed is found throughout the eastern and midwestern United States and Canada. It occurs from Prince Edward Island and Maine west to southern Manitoba [20,23,21]. Swamp milkweed continues southeast through the Midwest and Great Plains to Florida [6,15,18]. Its distribution extends westward to Texas and New Mexico [2,20,24]. Six disjunct areas of its range occur in southern Idaho, Wyoming, Nevada, and north, central, and south Utah [3,26].
States and Provinces
- United States: AZ CT FL GA ID IL IN LA ME MA MI MN MO NV NH NM ND OK RI SC SD TN TX UT VT VA WI WY
- Canada: MB NB NS ON PE PQ
Site Characteristics
Swamp milkweed is a semiaquatic plant [3]. It occurs in a range of wet conditions from standing water to saturated soil. A riparian species, it is found on streambanks, pond shores, banks, and floodplains of lakes, waterways, marshes, swamps, and wet areas of prairies [6,13,18,21]. Additionally, it occurs in wet meadows and in low wet woods [23].
Plant Communities
No entry.
Botanical Description
Swamp milkweed in bloom.
Swamp milkweed is an erect plant, 11 to 18 inches (0.3-0.5 m) tall, with milky sap. It has a short rootstock or caudex with shallow fibrous roots. A plant may have one to several leafy stems. Its lance-shaped, opposite leaves have short stalks. Flowers have many elaborate structures (e.g., hoods and horns) and are arranged in flesh-colored terminal umbels [23].
Raunkiaer Life Form (Raunkiaer 1934)
- Hemicryptophyte
Seasonal Development
Across its range, swamp milkweed begins to flower during the last week of June or the first week in July and continues until August or September [2,6,15,18,21,23]. Individual flowers remain open for about 1 week [9]. Fruits mature from August through October [2,6,15,18,21,23]. After maturation, follicles split open on one side to release seeds during October and November [23].
Regeneration Processes
Swamp milkweed readily germinates from seed shed the previous year (50 to 88 percent germination [11]) after cold stratification, 39 degrees Fahrenheit (4 deg C), for approximately 9 months. A plant puts up an average of one stem from a short caudex and sprouts each year from this rootstock. Flowers are insect pollinated (Hymenoptera and Lepidoptera) [10]. Seeds have long hairs that facilitate wind dispersal in the fall. Swamp milkweed is self-fertile [8]. It very rarely reproduces asexually by rhizomes [8].
Successional Status
Swamp milkweed is a colonizer. It has wind-dispersed seeds and can self-fertilize.
Immediate Fire Effects
No fire studies on this plant have been reported. A fire would kill swamp milkweed back to the caudex. In moist soil, the caudex is usually not deeply rooted. Death would depend upon fire severity. It may survive a cool fire. Late season (summer and fall) fires would have the greatest effect on this species. Since its seeds are not shed until October or November, a late season fire would kill the seed crop of the current year.
Postfire Regeneration Strategy (Stickney 1989)
- Survivor species; on-site surviving root crown or caudex
- Off-site colonizer; seed carried by wind; postfire years 1 and 2
Fire Adaptations
The moist habitat of swamp milkweed discourages fire entry. Swamp milkweed is very shallowly rooted; it would most likely be killed in a fire of any severity. Adjacent communities may serve as seed sources after a fire. Swamp milkweed is a component of prairie wetlands, so it has evolved with some fire exposure.
Plant Response to Fire
Following a cool surface fire, swamp milkweed sprouts from the caudex and produces fruit. If plants have been killed, off-site seeds will be wind dispersed into the burned area. This seed will germinate on burned areas during the first postfire growing season, provided soil conditions are wet.
Long-term response: Swamp milkweed should have no difficulties in maintaining populations. It can self-fertilize; sexual reproduction will continue, despite a reduced number of colonizing plants.
Plant recovery is controlled by the severity of the fire and availability of adequately wet habitat.
Fire Regimes
For fire regime information, search FEIS for this species by entering the species name or acronym on the home page and selecting “Fire Regime” as the publication type.
Fire Management Considerations
No entry.
Federal Status
None
Other Status
No entry.
Importance to Wildlife and Livestock
Swamp milkweed foliage and stems have been reported to cause mortality in sheep. It is not known why sheep are so susceptible [7,12]. Muskrats are unaffected by swamp milkweed and readily eat the roots [23].
Palatability and Nutritional Value
Milkweeds in general are not palatable to wildlife. The bitter milky juice is high in alkaloids [17]. Most animals avoid it unless forced to eat it on overgrazed pastures [17].
Cover Value
No entry.
Value for Rehabilitation or Restoration of Disturbed Sites
Swamp milkweed is currently used in Wisconsin for wetland rehabilitation [11]. It is included in commercially available seed mixes.
Other Uses
Swamp milkweed seeds have long hairs, called comas. Seed comas have been used as pillow and lifejacket stuffing [3,23]. Stem fibers have been suggested as substitutes for flax and hemp [3]. Young shoots, inflorescences, and leaves may be cooked with several changes of water and eaten [23]. This plant causes dermatitis.
Other Management Considerations
No entry.
Table A1— Forest and range ecosystems, Bureau of Land Management (BLM) physiographic regions, Kuchler plant associations, Society for American Foresters (SAF) forest cover types, and Society for Rangeland Management (SRM) rangeland cover types in which this species occurs.
Forest and Range Ecosystems (Garrison et al. 1977)
- FRES12 Longleaf - slash pine
- FRES13 Loblolly - shortleaf pine
- FRES15 Oak - hickory
- FRES16 Oak - gum - cypress
- FRES28 Western hardwoods
BLM Physiographic Regions (Bernard and Brown 1977)
- 6 Upper Basin and Range
- 8 Northern Rocky Mountains
- 10 Wyoming Basin
- 11 Southern Rocky Mountains
- 12 Colorado Plateau
- 13 Rocky Mountain Piedmont
- 14 Great Plains
Kuchler Plant Associations (Kuchler 1964)
- K025 Alder - ash forest
- K081 Oak savanna
- K082 Mosaic of K074 and K100
- K084 Cross Timbers
- K089 Black Belt
- K090 Live oak - sea oats
- K091 Cypress savanna
- K100 Oak - hickory forest
- K104 Appalachian oak forest
- K105 Mangrove
- K110 Northeastern oak - pine forest
- K111 Oak - hickory - pine forest
- K112 Southern mixed forest
- K113 Southern floodplain forest
- K114 Pocosin
- K115 Sand pine scrub
- K116 Subtropical pine forest
SAF Cover Types (Eyre 1980)
- 45 Pitch pine
- 50 Black locust
- 53 White oak
- 55 Northern red oak
- 57 Yellow-poplar
- 58 Yellow-poplar - eastern hemlock
- 59 Yellow-poplar - white oak - northern red oak
- 61 River birch - sycamore
- 64 Sassafras - persimmon
- 65 Pin oak - sweetgum
- 69 Sand pine
- 70 Longleaf pine
- 73 Southern redcedar
- 75 Shortleaf pine
- 79 Virginia pine
- 80 Loblolly pine - shortleaf pine
- 81 Loblolly pine - shortleaf pine
- 83 Longleaf pine - slash pine
- 84 Slash pine
- 87 Sweet gum - yellow-poplar
- 88 Willow oak - water oak - diamondleaf oak
- 89 Live oak
- 91 Swamp chestnut oak - cherrybark oak
- 96 Overcup oak - water hickory
- 97 Atlantic white cedar
- 101 Baldcypress
- 102 Baldcypress - tupelo
- 103 Water tupelo - swamp tupelo
- 104 Sweetbay - swamp tupelo - redbay
- 105 Tropical hardwoods
- 109 Hawthorn
- 110 Black oak
- 111 South Florida slash pine
- 222 Black cottonwood - willow
- 235 Cottonwood - willow
- 252 Paper birch
SRM Rangeland Cover Types (Shiflet 1994)
- No entry.
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