Asclepias speciosa

General: Milkweed Family (Asclepiadaceae). Asclepias flowers look like crowns, with the corolla reflexed and hoods elevated above the corolla. Showy milkweed (Asclepias speciosa) is a hairy perennial with stems ascending to erect. The leaves are opposite, persistent, with short petioles, elliptic to ovate blades, and bases rarely cordate and clasping. The corolla is reflexed and rose-purple; the hoods are elevated above the corolla in pink, aging yellow. Horns are exerted beyond the hoods.

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

Showy milkweed is native to and widely distributed in western North America. It occurs from southern Manitoba
west to British Columbia and south to Minnesota, to northwestern Texas, and California [17,44,61,63]. Plants database provides a distributional map of showy milkweed.
Precise distribution information is unavailable for all locations where showy
milkweed may occur.  The following lists are therefore speculative and not
exhaustive, and showy milkweed may be present in other vegetation types.

(key to state/province abbreviations)

UNITED STATES

AZARCACOIDILIAKSMIMNMTNENVNMNDOKORSDTXUTWAWIWY

CANADA
ABBCMBSK

More info on this topic.

This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

BLM PHYSIOGRAPHIC REGIONS [7]:

1 Northern Pacific Border

2 Cascade Mountains

3 Southern Pacific Border

4 Sierra Mountains

5 Columbia Plateau

6 Upper Basin and Range

7 Lower Basin and Range

8 Northern Rocky Mountains

9 Middle Rocky Mountains

10 Wyoming Basin

11 Southern Rocky Mountains

12 Colorado Plateau

13 Rocky Mountain Piedmont

14 Great Plains

15 Black Hills Uplift

16 Upper Missouri Basin and Broken Lands

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

Global Range: CA (Solano to Siskiyou counties, W. base of Sierra Nevada to Fresno and Inyo counties), WA, NV, MS.

For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site. Milkweed grows in clumps beside roadways and on abandoned farmlands and other open areas, reaching heights of 120 to 150 cm (4 to 5 ft) during the summer. Milkweed species grow throughout the United States. Showy milkweed occurs in many sunny, dry habitats including fields and roadsides, from 0 to 1900 m. The plant occurs in California to British Colombia and Central Canada south to Texas.

Asclepias giffordii Eastw.:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Asclepias speciosa Torr.:
Canada (North America)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

More info for the terms: follicle, forb, fresh, monoecious, root crown, warm-season

In the Willamette Valley of Oregon, showy milkweed grows primarily in open grasslands.
It sometimes occurs in riparian zones and savannas with small trees [27].

In plains grasslands of western Nebraska, showy milkweed is found in grama-buffalo grass (Bouteloua
spp.-Buchloe dactyloides), grama-needle-and-thread grass-western wheatgrass (Hesperostipa
comata-Pascopyrum smithii), and sandsage-bluestem (Artemisia filifolia-Andropogon/Schizachyrium
spp.) grasslands. Green needlegrass (Stipa viridula) and threadleaf sedge (Carex filifolia)
are common codominants within these grasslands [31].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Asclepias speciosa

• GENERAL BOTANICAL CHARACTERISTICS
• RAUNKIAER LIFE FORM
• REGENERATION PROCESSES
• SITE CHARACTERISTICS
• SUCCESSIONAL STATUS
• SEASONAL DEVELOPMENT

 
Charles Weber ©California Academy of Sciences

GENERAL BOTANICAL CHARACTERISTICS:

This description provides characteristics that may be relevant to fire ecology,
and is not meant for identification. Keys for identification are available [6,12,17,22,28,30,34,38,39,44,60,61,63].

Showy milkweed is a warm-season perennial forb [17,22,29,38,61,63]. Stems are
ascending to erect and 19.7 to 47.2 inches (50.0-119.9 cm) tall [6,17,22,24,28,38,44,61,63].
Leaves are 2.4 to 7.9 inches (8-20 cm) long
and ovate-lanceolate [6,22,24,44,61]. The inflorescence is a large, showy umbelliform cymes [6,22,63]. At 0.59 to
1.10 inch (15-28 mm) wide, they are the largest of all Asclepias species
[38,61]. The fruit is a 2.4- to 4.7- inch (6-12 cm) follicle [6,17,22,24,44]. Seeds are elliptic and 0.24 to 0.35 inch (6-9 mm) long
[6,17,22,63], with hair-like tufts (see photo above).
Showy milkweed has "deep" rhizomes [10,22].

RAUNKIAER [49] LIFE FORM:

Geophyte
Hemicryptophyte

REGENERATION PROCESSES:

Showy milkweed reproduces both sexually and vegetatively.

Breeding system:
Showy milkweed is monoecious.
Most Asclepias spp. are self-incompatible, requiring crosses between genetically
different individuals to produce viable seeds [11,63,65].
Pollination:
Showy milkweed is pollinated by wind and insects. Insect pollination
is accomplished by lepidopterans and hymenopterans. These
insects remove the pollen packet, or pollinarium, when a groove in the plant's corpusculum
entraps the hairs or appendages of the insect. The arms of the pollinarium twist, facilitating
insertion of the pollinarium into the stigmatic chamber of another flower as the
pollinating insect continues foraging [9,27,63,65]. The flowers
of Asclepias spp. produce large amounts of nectar, which serves as a
germination medium for the pollen [65].
Seed production:
Stevens [54] determined that showy milkweed produces an average of 630 seeds per stem
with a weight of 0.208 ounce (5.890 g) per 1,000 seeds.

Seed dispersal:  Seeds are
dispersed when wind catches the hair-like seed tufts. [10]. Showy milkweed's
persistence along waterways [6,12,17,28,30,34,38,42,44,53,60,61]
also suggests dispersal by water [14].
Seed banking:
Seed may be stored in water or in soil, as shown in the following studies. In
a study by Bruns [14] in the Chandler Power Canal in Prosser, Washington, showy
milkweed seeds survived in fresh water for several months. Three sets of seeds
were submerged in fresh water up to 12 months to
determine viability.  Extended viability of seeds indicates the potential
of seeds trapped or carried in irrigation water as sources of potential sources
of colonization. The following table represents the percentage of seeds
that were decomposed after 3 to 12 months of submergence in fresh water, and
germination of the submerged and dry-stored seeds after the same periods [14]:
Months after test initiated036912Percent of submerged seeds that decomposed----124848Percent germination of submerged seeds----9690545Percent germination of dry-stored seeds414142612
Chepil's [15] study suggests that showy milkweed has a short-lived soil seedbank.
In a study performed in Saskatchewan, showy milkweed seeds were tested for
longevity, periodicity of germination, and viability of seeds in cultivated soil.
One thousand seeds were mixed in a 2.5-inch
(6.4 cm) layer of sterilized
soil in the field. From 15 November to 31 March, the soil was turned with a
trowel to a 3-inch (7.6 cm) depth 2-3 times, then sown to spring wheat (Triticum aestivum) or
cereal barley (Hordeum vulgare) in alternate years.
Ninety-five percent or more of the showy milkweed seeds germinated during the 1st year, with
the greatest germination from 7 May to 31 May, though substantial
amounts of seeds germinated until 31 July. Overall, showy milkweed seed dormancy did not
exceed 2 years [15].
Germination:
Seeds can germinate in soil or when submerged in water, although submergence may lower the
germination rate if the seeds remain in water over 36 months.
The longevity of showy milkweed seeds in fresh water was
tested by Comes and others [16]
in the Chandler Power Canal in Prosser, Washington. One hundred showy milkweed
seeds were collected from the field; dried; placed separately into nylon cloth
envelopes; placed in plastic screen bags; and
submerged 11.8 inches (30 cm) beneath the water surface. Comparative germination tests were
made on seeds that had been stored dry in glass bottles at room temperature
[16]:

Months after test initiated

3691224364860

%

Germination of submerged seeds13393857100Submerged seeds remaining firm554732147300Germination of dry-stored seeds7270686958654571
Germination in water was at a maximum level of 55% between 3 and 12
months, and no germination occurred after 48 months. Germination of dry-stored
seeds at the 3- to 6-month period ranged from 45% to 72% [16].
Seedling establishment/growth:
During the seedling stage, showy milkweed directs most of its energy
into root development. This contributes to drought tolerance, but the
aboveground portions of showy milkweed grow "very slowly" [2].
Asexual regeneration: Showy
milkweed spreads clonally from deep rhizomes [10,22], and probably from from
sprouting from the root crown.

SITE CHARACTERISTICS:

Showy milkweed prefers wet areas of prairie habitats and moist,
sandy soils along waterways, ditches, streambanks, floodplains, and washbottoms. 
It is common along the banks of irrigation ditches
[1]. It can become weedy in cultivated fields, roadsides, railways, "wastelands," and
fence rows [6,12,17,28,30,34,38,42,44,53,60,61].

Elevation:
Showy milkweed occurs at the following elevations:
Arizona6,000-9,000 feet (1,800-2,700 m) [39]California 0-600 feet (0-1,900 m) [28]Colorado3,500-7,500 feet (1,100-2,300 m) [24]Nevada2,200-8,500 feet (700-2,600 m) [38]New Mexico6,000-9,000 feet (1,800-2,700 m) [44]Utah 2,700-8,500 feet (800-2,600 m) [61]
Soil:
Showy milkweed prefers moist soil [6,12,17,28,30,34,38,42,44,53,60,61].
It grows in all soil textures [53] and tolerates alkaline soils [17].

SUCCESSIONAL STATUS:

Little research has been done addressing the successional status of showy
milkweed; however, it is considered a "weedy" species [1,17] that
occurs in early and mid-succession. It has the
ability to quickly colonize disturbed sites (Riser, personal communication [50])
in open grasslands and partially shaded habitats.

SEASONAL DEVELOPMENT:

Across showy milkweed's range, flowering occurs from May to August
[10,17,22,39,44,45,63]. Follicles dry during August and September,
and seeds disperse in September and October [10].

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This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):

More info for the term: cover

SRM (RANGELAND) COVER TYPES [52]:

201 Blue oak woodland

202 Coast live oak woodland

203 Riparian woodland

204 North coastal shrub

205 Coastal sage shrub

214 Coastal prairie

215 Valley grassland

310 Needle-and-thread-blue grama

605 Sandsage prairie

607 Wheatgrass-needlegrass

608 Wheatgrass-grama-needlegrass

611 Blue grama-buffalo grass

614 Crested wheatgrass

704 Blue grama-western wheatgrass

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This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

More info for the term: cover

SAF COVER TYPES [19]:

63 Cottonwood

222 Black cottonwood-willow

244 Pacific ponderosa pine-Douglas-fir

245 Pacific ponderosa pine

246 California black oak

250 Blue oak-foothills pine

255 California coast live oak

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the term: shrub

KUCHLER [41] PLANT ASSOCIATIONS:

K010 Ponderosa shrub forest

K011 Western ponderosa forest

K030 California oakwoods

K035 Coastal sagebrush

K065 Grama-buffalo grass

K070 Sandsage-bluestem prairie

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

ECOSYSTEMS [20]:

FRES17 Elm-ash-cottonwood

FRES21 Ponderosa pine

FRES28 Western hardwoods

FRES34 Chaparral-mountain shrub

FRES37 Mountain meadows

FRES38 Plains grasslands

FRES39 Prairie

FRES40 Desert grasslands

FRES42 Annual grasslands

Comments: Dry, gravelly, stony places, yellow pine forests, mixed evergreen forest, coastal range under 6000 feet.

Collect seeds after pods have ripened, but before they have split open. The seeds are wind dispersed, so be careful when gathering to place in a paper or burlap bag to avoid seed lost. Seeds can be directly sewn into the ground in the fall. The seed is very viable. Planting seed the first fall after collecting seeds maximizes revegetation success. It is not certain how long seeds can be stored.

Cold treatment for three months improves seed germination in some milkweed species from higher elevations or colder climates (where it freezes in the winter). Revegetation success with milkweeds seems to be improved by planting seeds directly in the ground. High mortality seems to occur with plants in pots and they don't overwinter well in pots. Milkweed plants naturally die back in winter, but re-emerge during the following spring unless planted in a pot

Whole Plant Collections: For milkweed species with rhizomes, propagation by cuttings of the tuberous rhizome is also easy and reliable. The cuttings should be made when the plant is dormant. Each piece of the rhizome should have at least one bud (they are about two inches apart). Timing of propagation is important. Harvest or divide plants and move them in October at the beginning of the rainy season. Place the plants in the ground by late fall so they can develop enough root growth to survive the winter. Irrigation the first year will improve survival, and by the second year the root system should be well enough established so plants will survive on their own. Both seedlings and cuttings will usually bloom in their second year, although cuttings will occasionally bloom during their first year (Kindscher 1992).

More info for the term: fire management

With light, wind-blown seed, deep rhizomes, and early successional status,
showy milkweed has adaptations that usually promote fire survivorship and
establishment in early postfire communities [55]. However, since data on
postfire regeneration of showy milkweeds are lacking, caution is recommended
when using prescribed burning if promoting showy milkweed is a fire
management objective. Small-scale burning and postfire monitoring can help
managers determine how showy milkweed responds to prescribed burning in a given
management area.

More info for the terms: cyme, forb

Research conducted on milkweeds of similar growth form may also apply to showy
milkweed. Mead's milkweed (Asclepias meadii) is a closely related, rhizomatous forb that grows in
the prairie states. In a study by Bowles
and others [13], prescribed burning during the dormant season
(before May) had either positive or neutral effects on seedlings on Preserves in
Missouri, Illinois, Iowa, and Kansas. Mead's
milkweed plants on burn plots produced more cymes, as well
as more flowers per cyme, compared to plants on unburned control plots [13].

More info for the term: root crown

Limited information suggests that showy milkweed establishes from seed after
fire [13]. As in many prairie plants, dormant-season fire
stimulates postfire flowering [8], so it is likely that showy milkweed
established from on-site seed as well as seed blown in from off-site seed
sources.

Showy milkweed probably also sprouts from rhizomes and the root crown after fire,
although such documentation is lacking. Research is needed on the fire ecology
of showy milkweed.

The immediate effect of fire on showy milkweed is not documented; however, fire
likely top-kills showy milkweed. Soil-stored seed and rhizomes are probably insulated from
fire damage.

More info for the terms: rhizome, root crown

POSTFIRE REGENERATION STRATEGY [55]:

Rhizomatous herb, rhizome in soil

Caudex/herbaceous root crown, growing points in soil

Geophyte, growing points deep in soil

Ground residual colonizer (on-site, initial community)

Initial off-site colonizer (off-site, initial community)

Secondary colonizer (on-site or off-site seed sources)

More info for the terms: fire regime, fuel, natural, root crown, severity

Fire adaptations:
There is no information in the literature regarding fire adaptations of showy milkweed;
however, showy milkweed likely regenerates from both seed and by sprouting from eeply buried rhizomes and
the root crown after fire. Prolific production of hairy, light seeds allows for wind
dispersal onto burns, with plants on adjacent unburned sites serving as seed
sources after fire. Showy milkweed seed can be stored in the soil for up to 2
years [15]. Seeds also have the ability to float and survive up to 36 months in water [16], allowing
another mechanism of travel after a burn. Further research is needed on fire
adaptations of showy milkweed.

FIRE REGIMES:
Historically, fire has been an important natural component of the savanna and
grassland communities where showy milkweed occurs [32]. Ponderosa pine and oak
savannas typically experienced fire at less than
10-year intervals [4,23]. Across the Great Plains, fires may have occurred as frequently
as every 1 to 10 years prior to European settlement [40,47]. Frequent fires
in plains grasslands affects species composition and vegetation dynamics [47],
and may favor sprouting species such as showy milkweed.
Riparian zones within mountain and plains grasslands historically had longer
fire-return intervals than surrounding vegetation. Typically burning
during drought, riparian zones usually have heavier fuel loads and burn with
higher severity than surrounding plant communities [4,5].
The following table provides fire return intervals for plant communities and
ecosystems where showy milkweed is important. For further information, see the
FEIS review of the dominant species listed below. This list may not be inclusive
for all plant communities in which showy milkweed occurs.
If you are interested in plant communities or ecosystems that are not listed below, see the complete FEIS fire regime table.
Community or ecosystemDominant species Fire return interval range (years)bluestem prairieAndropogon gerardii var. gerardii-Schizachyrium scoparium 40,47]coastal sagebrushArtemisia californica 47]plains grasslandsBouteloua spp. 47,64]blue grama-needle-and-thread grass-western wheatgrassBouteloua gracilis-Hesperostipa comata-Pascopyrum smithii 47,51,64]California steppeFestuca-Danthonia spp. 47,56]wheatgrass plains grasslandsPascopyrum smithii <5-47+ [47,48,64]Pacific ponderosa pine*Pinus ponderosa var. ponderosa 1-47California oakwoodsQuercus spp. <35 [3]coast live oakQuercus agrifolia 2-75 [23]blue oak-foothills pineQuercus douglasii-P. sabiniana 3]California black oakQuercus kelloggii 5-30 [47]

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 1
Specimens with Barcodes: 1
Species With Barcodes: 1

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: NNR - Unranked

Rounded Global Status Rank: G5 - Secure

Reasons: Element found throughout the Great Plains on sandy, loamy, or rocky soils in flood plains, abundance unknown.

United States

Rounded National Status Rank: NNR - Unranked

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Wide range, abundance not known.

Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status and wetland indicator values.

Control:
Showy milkweed interferes with crops, and is an agricultural pest [1].

In a study by Whitson and Schwope [62], 8 herbicides were tested on showy
milkweed on an irrigated grass pasture near Lovell, Wyoming. The effects of
differing rates of the herbicides are provided in [62].

Seeds and plants of selected Asclepias cultivars are available from many nurseries. It is best to plant species from your local area, adapted to the specific site conditions where the plants are to be grown.

When used for fiber, milkweed is collected in the autumn after the leaves have begun to senesce or dry up. Plants grow in places that have been disturbed such as road grading, construction sites, logging landing fills, and etc. Pete Bunting (pers. comm. 2-9-1999) says, "In the fall when the milkweed has dried I check to see if they will break off at the ground line. The plants are usually a yellow tan to gray depending on how long they have dried. I like the gray for softer string, but the fibers are shorter. The tan stalks have longer fibers but are also stiff and hard to work but very long. I break off as many of the plants as I can gather as they are going to resprout in the spring. I try and let them dry some more. Then I process them. I have used plants that have over-wintered under snow and they were fine but had soft, short fiber. After 2 winters they are usually no good but you have another year's stalks to pick by then." The dried stalks are then split open and the fibers are twisted into string.

Both milkweed and dogbane were burned in the fall by California Indian tribes to eliminate dead stalks and stimulate new growth. Burning causes new growth to have taller, straighter stems with longer fibers. It also stimulates flower and seed production.

Warning: Milkweed may be toxic when taken internally, without sufficient preparation.

Ethnobotanic: People have used milkweed for fiber, food, and medicine all over the United States and southern Canada. Fibers from the stems of milkweed have been identified in prehistoric textiles in the Pueblo region. Tewa-speaking people of the Rio Grande still make string and rope from these fibers. At Zuni, the silky seed fibers are spun on a hand-held wooden spindle and made into yarn and woven into fabric, especially for dancers. Pueblo people ate green milkweed pods and uncooked roots from one of the species that forms fleshy tubers underground.

Milkweeds (especially Asclepias speciosa) supply tough fibers for making cords and ropes, and for weaving a coarse cloth. Milkweed stems were collected after the stalks dried in late fall early winter. The dried stalks were split open to release the fibers; milkweed fibers were sometimes mixed with fibers of Indian-hemp (Apocynum cannabinum). The bark is removed and the fibers released by first rubbing between the hands and then drawing the fibers over a hard surface. Twisting the fiber opposite each other and twining them together formed the cord; often this was accomplished by rolling the fibers on the thigh while twisting them together.

Vast quantities of fiber plants are required for the making of nets, regalia, and cordage by California Indians. Blackburn and Anderson (1993) quote Craig Bates of the Yosemite Museum that it takes approximately five stalks of milkweed or Indian hemp to manufacture one foot of cordage. A Sierra Miwok feather skirt or cape contain about 100 feet of cordage made from approximately 500 plant stalks, while a deer net 40 feet in length contained some 7,000 feet of cordage, which would have required the harvesting of a staggering 35,000 plant stalks, (Barrett and Gifford 1933:178).

The young shoots, stems, flower buds, immature fruits, and roots of showy milkweed were boiled and eaten as a vegetable by various indigenous groups of eastern and mid-western America.

In some areas the young leaves and stems were used as greens. The flowers were also eaten raw or boiled, and the buds were boiled for soup or with meat. The most common use for these plants, recorded among almost all the tribes throughout California, was to obtain a kind of chewing gum from the sap of Asclepias speciosa. The sticky white sap was heated slightly until it became solid, then added to salmon fat or deer grease.

The sap of Asclepias speciosa was used as a cleansing and healing agent by some of the desert tribes for sores, cuts, and as a cure for warts and ringworm. The silky hairs were burned off the ripe seeds, which were then ground and made into a salve for sores. Seeds were boiled in a small amount of water and the liquid used to soak rattlesnake bites to draw out the poison. A hot tea made from the roots was given to bring out the rash in measles or as a cure for coughs. It was also employed as a wash to cure rheumatism. The mashed root, moistened with water, was used as a poultice to reduce swellings.

Insectary: Milkweed species are attractive to butterflies, bees, and other insects. Accordingly, this is a wonderful horticultural plant for beautiful floral landscaping that attracts butterflies (particularly Monarchs) and other insects.

Monarch butterflies are specific to milkweed plants. This is the only type of plant on which the eggs are laid and the larvae will feed and mature into a chrysalis. Eggs are laid on the underside of young healthy leaves. It is important to have large clumps of milkweeds for the young caterpillars; their response to predation is to drop to the ground and "play possum." They cannot find their way back to the milkweed stems, which they need to survive, unless they are fairly densely spaced.

Monarch, Queen and Viceroy butterflies are Müllerian mimics; all are toxic, and have co-evolved similar warning patterns to avoid predation. Other insects, which utilize milkweed, are the large milkweed bug, common milkweed bug, red milkweed beetle, blue milkweed beetle, and bees.

Toxicity: Milkweed sap contains a lethal brew of cardenolides (heart poison), which produces vomiting in low doses and death in higher doses. Chemicals from the milkweed plant make the monarch caterpillar's flesh distasteful to most animals. At one time, milkweed was classified as a noxious weed due to reported toxic effects on livestock, and efforts were made to eradicate it. Milkweeds are thought to be poisonous to cows and sheep.