裸穗豬草

More info for the terms: fire use, prescribed fire, woodland

Response of vegetation to prescribed burning in a Jeffrey pine-California
black oak woodland and a deergrass meadow at Cuyamaca State Park,
California, provides information on prescribed fire use and postfire
response of many mixed-conifer woodland species including Cuman ragweed.

Cuman ragweed
common ragweed
perennial ragweed
western ragweed

The degree to which Cuman ragweed provides environmental protection
during one or more seasons for wildlife species is as follows:

                                MT      UT      WY
        Pronghorn              ----    Poor    Poor
        Elk                    ----    Poor    Poor
        Mule deer              ----    Poor    Poor
        White-tailed deer      ----    ----    Poor
        Small mammals          Poor    Fair    Poor
        Small nongame birds    Poor    Fair    Poor
        Upland game birds      ----    Poor    Poor
        Waterfowl              ----    Poor    Poor

More info for the terms: forb, monoecious, warm-season

Cuman ragweed is a warm-season, native perennial forb.  The main stem
rises from shallow (2 inches [5 cm]) or deep, branching rhizomes which
extend down 3 to 6 feet (0.9-1.8 m) [6,70].  Stems are slender and
branched, usually 1 to 2 feet (30-60 cm) tall [59,70].  Plants are
monoecious with unisexual flowers; male flowers occur at the top of the
plant and female flowers are axillary [41].  Achenes have a short beak
and small blunt tubercles on top [41].

Cuman ragweed's range extends from southern British Columbia east to
Nova Scotia [51,81,107] and southward through the United States from the
Appalachians to the West Coast and into central Mexico
[38,74,90,104,108].  Cuman ragweed was introduced from North America
into Europe and southwestern Russia [115].

More info for the term: fire regime

As a component of North American grasslands, Cuman ragweed has evolved
with fire.  Soil can insulate roots from lethal temperatures during a
fire.  Surface rhizomes of Cuman ragweed may be killed during a fire;
however, the plant also has deep-seated rhizomes which would survive
most fires [6].

FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find FIRE REGIMES".

Cuman ragweed has been classified as an increaser (by 100 percent or
more) on burned plots [77].

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More info for the term: geophyte

Geophyte

More info for the terms: codominant, forb, forbs, grassland, heath, shrub, shrubs

Cuman ragweed grows in grasslands, savannas, and woodlands across
North America.  In addition to occurring in its native settings (such as
dry prairies, blowouts, washouts, sandy woods, meadows, and hills),
Cuman ragweed is a widespread weed in waste places, roadsides,
railroads, overgrazed rangeland, and other disturbed places
[41,75,99,107,126].

Climate ranges from continental to coastal with short, warm to hot
summers and long, cold winters [1,3,16,129].  Often, there are
moderately strong surface winds [1].  Humidity is semiarid to moist
subhumid [42,44,86].  Annual precipitation ranges from 5 to 34 inches
(114-880 mm) with 60 to 80 percent occurring during the growing season
[19,23,39,56,75,114,125].  Temperatures vary from an average 72 degrees
Fahrenheit (22 deg C) in July to a January average of 11 degrees
Fahrenheit (-11.5 deg C) [124].

Cuman ragweed grows at elevations ranging from 850 to 7,400 feet
(259-2,256 m) and in many types of soils [18,30,60,66,69].  Soil
textures are predominantly loams, varying from silty clay loams to fine
sandy loams [23,61,122].  Soil pH ranges from 5.7 to 7.9 [22,105].
Soils often have little organic matter and are low in fertility [34].

Cuman ragweed occurs in too many grassland ecosystems for associated
species to be reviewed here.  Listed below are some typical examples of
major grasslands and the plant components found with Cuman ragweed.
In addition to this brief listing, the reader is referred to specific
examples of more distinct and diverse grasslands in which western
ragweed occurs [11,15,18,19,20,22,25,26,28,29,32,33,39,42,49,129].

Southern Great Plains
Shortgrass prairie is dominated by buffalo grass (Buchloe dactyloides)
and blue grama (Bouteloua gracilis) with sand dropseed (Sporobolus
cryptandrus [132].  When trees occur, sand shinnery oak (Quercus
havardii) is dominant [45,118].

Mixed-grass prairie is dominated by sideoats grama (Bouteloua
curtipendula), buffalo grass, little bluestem, and tobosagrass (Hilaria
mutica) [132].  When an overstory is present, dominant trees are honey
mesquite (Prosopis glandulifera), Ashe juniper (Juniperus ashei), post
oak (Quercus stellata), blackjack oak (Q. marilandica), and live oak (Q.
virginiana) [59,67,86,112].  Shrubs include cholla (Opuntia imbricata),
common broomweed (Xanthocephalum dracunculoides), and whitebrush
(Aloysia lycoiodes) [47,66,123].  An associated forb is Riddel daisy
(Aphanostephus riddellii) [47,65].

Tallgrass prairie is dominated by little bluestem, silver bluestem
(Andropogon saccharoides), and fewflowered panic (Dicanthelium
oligosanthes) [36].

Central Great Plains Shortgrass dominated by blue grama with
buffalograss, sand reedgrass (Calamovilfa longifolia), and prairie
dropseed (Sporobolus heterolepis) [82,122,132].  An associated forb is
horseweed (Conyza canadensis) [43].

Northern Great Plains Tallgrass prairie is dominated by big bluestem
with little bluestem, Indiangrass (Sorghastrum nutans), and switchgrass
(Panicum virgatum) [132].  A shrub co-occurring with Cuman ragweed is
Louisiana sandwort (Artemisia ludoviciana) [120].  Codominant forbs are
heath aster (Aster ericoides), purple prairie-clover (Petalostemum
purpureum), and goldenrods (Solidago spp.)  [1,35,106,120].

Cuman ragweed occurs on floodplain woodlands with sand reedgrass and
Canadian wildrye (Elymus canadensis) [4,117].  The overstory is
dominated by floodplain cottonwood (Populus deltoides) with green ash
(Fraxinus pennsylvanica) [117].

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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):

    40  Post oak - blackjack oak
    42  Bur oak
    66  Ashe juniper - redberry (Pinchot) juniper
    68  Mesquite
    72  Southern scrub oak
    73  Southern redcedar
    89  Live oak
   220  Rocky Mountain juniper
   235  Cottonwood - willow
   238  Western juniper
   242  Mesquite
   244  Pacific ponderosa pine - Douglas-fir
   255  California coast live oak

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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):

More info for the term: shrub

   FRES15  Oak - hickory
   FRES21  Ponderosa pine
   FRES31  Shinnery
   FRES32  Texas savanna
   FRES33  Southwestern shrubsteppe
   FRES34  Chaparral - mountain shrub
   FRES38  Plains grasslands
   FRES39  Prairie
   FRES42  Annual grasslands

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

   K033  Chaparral
   K035  Coastal sagebrush
   K053  Grama - galleta steppe
   K054  Grama - tobosa prairie
   K057  Galleta - three-awn shrubsteppe
   K058  Grama - tobosa shrubsteppe
   K060  Mesquite savanna
   K061  Mesquite - acacia savanna
   K062  Mesquite - live oak savanna
   K063  Foothills prairie
   K064  Grama - needlegrass - wheatgrass
   K065  Grama - buffalo grass
   K067  Wheatgrass - bluestem - needlegrass
   K068  Wheatgrass - grama - buffalo grass
   K069  Bluestem - grama prairie
   K070  Sandsage - bluestem prairie
   K071  Shinnery
   K074  Bluestem prairie
   K075  Nebraska Sandhills prairie
   K076  Blackland prairie
   K078  Southern cordgrass prairie
   K081  Oak savanna
   K084  Cross Timbers
   K085  Mesquite - buffalo grass
   K086  Juniper - oak savanna
   K087  Mesquite - oak savanna
   K100  Oak - hickory forest

Cuman ragweed is top-killed by fire.  Shallow rhizomes may be killed
along with seeds on aerial stems.

More info for the term: forbs

Managers rate the forage value of Cuman ragweed as fair [121].  The
foliage and stems contain cinnamic acid and sesquiterpene lactones that
deter herbivory [129].  However, Cuman ragweed is not considered a
poisonous plant [88].  It is moderately important as ungulate forage
[24,31,48,98,103].  Cuman ragweed is used for food and nesting
material, and as a habitat component by small mammals and nongame birds
[10,52,63].  Cuman ragweed is an important food (seeds and foliage) on
activity sites for upland gamebirds [11,73,110,123].  In a study of the
relationship of grasshoppers to different pasture treatments and range
sites in Kansas tallgrass prairie, Cuman ragweed was one of the two
most abundantly available and most ingested forbs [78].

More info for the terms: codominant, forb, habitat type

Cuman ragweed is a principal or dominant forb in many grasslands, such
as little bluestem (Schizachyrium scoparium) and shortgrass communities
[6].  It is of secondary importance in big bluestem (Andropogon gerardii
var. gerardii) communities, but it is still the dominant forb [6,113].
It is a dominant forb in the Cross Timbers range, sand plains, and
prairies of Texas [44,86].  Cuman ragweed is dominant in sand
tallgrass prairies and sand hills of the Midwest [105,120].  It is the
principal forb in the shortgrass-ponderosa pine (Pinus ponderosa)
woodlands of north-central Arizona [18,28,60].  Cuman ragweed is
present in the Gambel oak (Quercus gambelii) grasslands of the west
[29,39].  Cuman ragweed is codominant in saltgrass (Distichlis
spicata) communities and in grasslands found above salt marshes [22,26,
34,42].

In riparian habitat types of Wyoming, Cuman ragweed is listed as
codominant with western wheatgrass (Pascopyrum smithii) in the
Grass/Sedge Meadow subtype [90].  Cuman ragweed is a important forb,
but not an indicator, in steppe habitat types of North Dakota and South
Dakota:  (1) needle-and-thread grass (Stipa comata)/threadleaf sedge
(Carex filifolia), (2) green ash (Fraxinus pennsylvanica)/common
chokecherry (Prunus virginiana), and in Montana:  (1) needle-and-thread
grass/sun sedge (Carex heliophila), (2) Idaho fescue (Festuca
idahoensis)/sun sedge, (3) bluebunch wheatgrass (Pseudoroegneria
spicata)/sideoats grama (Bouteloua curtipendula), (4) bluebunch
wheatgrass/threadleaf sedge, (5) fragrant sumac (Rhus aromatica)/
bluebunch wheatgrass, and (6) fragrant sumac/Idaho fescue [64].

Publications that list Cuman ragweed as dominant are:

(1)  The vegetation of the Grand River/Cedar River, Sioux, and Ashland
     Districts of the Custer National Forest: a habitat type
     classification [64].
(2)  A physical and biological characterization of riparian habitat and its
     importance to wildlife in Wyoming [90].

More info for the term: forb

Forb

More info for the terms: cover, duff, formation, litter

Cuman ragweed is one of the main hay-fever plants in late summer when
it is in bloom [70,74,130].

Cuman ragweed is a major invader of deteriorating rangeland.  It
readily moves into open habitat in prairies [19,121].  Cuman ragweed
is not drought resistant.  It was partially or totally eliminated from
mixed-grass prairies during the drought of the 1930s; however, western
ragweed recovered by the mid-1940s [40,121].

Livestock:  Cuman ragweed averaged 1,200 pounds of dry matter per acre
(1,342 kg/ha) on a clay upland range site near Hays, Kansas, and was
beneficial to grass production [83].  Grass yields were never less than
2,000 pounds per acre (2,237 kg/ha) from sites that produced 7,000
pounds per acre (7,830 kg/ha) Cuman ragweed [83].  A buildup of 3 to 5
inches (8-13 cm) of grass mulch on a lightly grazed rangeland delayed
Cuman ragweed growth in the spring; however, litter increased the
moisture supply [71,122].

For optimum use of Cuman ragweed on shortgrass rangeland, continuous
season-long or year-long grazing at moderate stocking rates, combined
with spring burning, is recommended [83].  Launchbaugh and Owensby [83]
recommend grazing Cuman ragweed early in the growing season.  Range
cattle consume Cuman ragweed by choice most heavily in April [48].

Cuman ragweed cover increases when it is grazed or disked
[44,57,94,123].  There was no significant (P>0.05) difference in
relative abundance of Cuman ragweed under moderate or heavy stocking
rates [67,69].  However, Cuman ragweed cover was significantly greater
on continuously grazed pasture compared with short duration grazing
[31,45].  Cuman ragweed herbage was significantly higher under thinned
ponderosa pine compared to unthinned areas [28].  Herbage production of
Cuman ragweed decreased as the depth of humus, duff, and litter
increased under ponderosa pine canopies [29].

Chemical Control:  Herbicide should be applied to Cuman ragweed during
the late vegetative stage before the formation of flowerbuds; western
ragweed is moderately or totally resistant during other growth phases
[93,111].  Before flowering, it is susceptible and may be controlled
with one foliage spray application at 1 pound active ingredient per acre
(1.1 kg ai/ha) for 2,4-D, 2,4,5-T, Silvex, 2,4,-D-B or 0.25 pound active
ingredient per acre (0.28 kg ai/a) Grazon PC and Banvel [43,83,93].
Grazon P + D will give control for more than 1 year [43].

Cuman ragweed root exudate significantly inhibited the formation of
nodules on legume roots, which decreases their ability to fix nitrogen
[128].

Cuman ragweed responds differently to different combinations of
disturbance and burning.  Cuman ragweed occurred significantly more on
unburned pocket gopher mounds than on burned; it occurred less
frequently on ant hills than on controls [55].  Cuman ragweed had
significantly higher average cover on burned areas immediately outside
of buffalo wallows compared to unburned controls [36].

Mature Cuman ragweed seeds from an eastern Texas prairie contained 1
to 3 percent silica, which reduces digestibility; the seeds had 70 to
less than 90 percent dry matter digestibility [109].  However, the seeds
contained more than 25 percent protein.  Forage quality (seasonal crude
protein content and digestibility) of Cuman ragweed on a Texas range
was higher after spring burning [17].

     AZ  CA  CO  CT  ID  IL  IA  KS  LA  ME
     MA  MI  MO  MN  MT  NE  NH  NC  ND  OH
     OK  OR  SC  SD  TX  UT  VT  WA  WI  WY
     AB  BC  MB  NS  ON  PE  PQ  SK  MEXICO

Cuman ragweed was used for medicinal purposes by American Indians.
Pueblo women in New Mexico drank a tea made from Cuman ragweed during
difficult labors at childbirth, and the Cheyenne of the Central Plains
used it to treat intestinal problems and colds [12].  Kiowa of Oklahoma
rubbed a preparation of Cuman ragweed on the sores of humans and
horses [12].

Ragweeds are normally considered to be unpalatable but when treated with
2,4-D become palatable.  Treated plants may, however, accumulate
nitrates to a toxic level [76].  In Montana, Utah, and Wyoming, western
ragweed palatability is poor for ungulates and waterfowl.  Its
palatability has mixed ratings for the following species:

                           MT      UT      WY
    Small mammals                 Poor    Good
    Small nongame birds   Good    Poor    Good
    Upland game birds     Fair    Poor    Fair

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Cuman ragweed is widespread, so specific dates for phenological stages
vary; however, stages of growth occur seasonally.  The months in
parentheses represent the center of its distribution.  Cuman ragweed,
a warm season plant, overwinters as a rosette [103].  In mid-spring
(April), seedlings germinate, and rosettes begin active growth of main
stems.  In late summer (August), Cuman ragweed flowers, and seedlings
may germinate with adequate rainfall [5].  It is at this time of year
that Cuman ragweed usually has its greatest biomass [96].  Flowering
continues through autumn [17,41,51,81,89,99].  Fruits form and seeds
disseminate through the late fall and winter (October to December) [5].
Aerial stems are killed by frost.

More info for the terms: cover, density, grassland

Season of burning, community type, and subsequent environmental
conditions determine Cuman ragweed response to burning.  In some
studies, no significant (P>0.05) difference was found in Cuman ragweed
postfire herbage, cover, or occurrence, despite the season burned
[4,72,79,82,92,131].

Cuman ragweed cover was significantly decreased by annual spring
burning in tallgrass prairies [2] and by a single spring fire in a
tobosa grassland ([66], see the Research Project Summary for more
information on this study). However, other studies showed that western
ragweed significantly increased in cover or was more abundant on spring
burned grasslands and oak savanna [7,13,68,124].  Late spring burning
decreased Cuman ragweed cover, and winter burning increased it [4,15,20]. 
The density of Cuman ragweed was increased by annual fall (October)
burning [16,21,106].

One year postfire, Cuman ragweed cover was significantly less on
burned areas compared to unburned areas [19].  Prescribed burning in
juniper (Juniperus spp.) communities of Texas in late winter or early
spring increased Cuman ragweed density 1 year postfire [100].  The
second and following years showed no further effects on Cuman ragweed
densities [100].

After a spring (May) fire in a Kansas tallgrass prairie, Cuman ragweed
increased significantly by year 3 in number of stems per 3.3 square feet
(1 sq m) [46].  Other tallgrass prescribed spring fires were conducted
annually and on a 4-year rotation.  Cuman ragweed cover was
significantly greater on the 4-year rotation compared to the annual
burning [3].  Four-year fire rotation was used to compare vegetative
response on shallow upland soils with lowland soils in tallgrass prairie
in Kansas.  Cuman ragweed was significantly more abundant on the
shallow upland soils after burning [54].

More info for the terms: herb, rhizome, secondary colonizer

Geophyte, growing points deep in soil
Rhizomatous herb, rhizome in soil
Secondary colonizer - off-site seed

More info for the terms: density, fruit, seed

Cuman ragweed colonizes sites by means of spreading rhizomes in the
surface 2 inches (5 cm) of soil, allowing it to propagate when
conditions are unfavorable to seedling establishment [6,48,127].
Cuman ragweed exhibits nonrandom replacement of ramets, which allows
it to exploit areas favorable to growth [87].

Seeds are reported to migrate into disturbed areas; however, the means
of dissemination was not identified [6].  In a germination trial using 1
square foot (0.09 sq. m) soil samples, Cuman ragweed seedlings did not
appear until week 6 or 7 [84].  After this time, seeds continued to
germinate for 3 weeks [84].

Once seeded into an area, Cuman ragweed may not set fruit until the
second year [37].  Under dry conditions, seed production is somewhat
inversely proportional to plant density.  A dense stand of western
ragweed in a dry summer resulted in stunted growth, and most plants died
without fruiting [72].

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):

    3  Southern Pacific Border
    5  Columbia Plateau
    7  Lower Basin and Range
   10  Wyoming Basin
   12  Colorado Plateau
   13  Rocky Mountain Piedmont
   14  Great Plains
   16  Upper Missouri Basin and Broken Lands

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More info for the terms: climax, codominant, cover, forb, formation, frequency, phase, succession

Differing sets of seral stages have been suggested for secondary
succession in prairie ecosystems, and Cuman ragweed has been reported
to occur in all of them and in climax communities [97,102].  Western
ragweed establishes in closed communities that are opened up by heavy
grazing or other disturbance [103].  In old field succession, western
ragweed was present as a principal forb in stands aged 0 to 5 years and
was present with 4 to 15 percent cover after 23 to 29 years [33,48].  On
abandoned black-tailed prairie dog towns, Cuman ragweed was codominant
with an annual grass, prairie threeawn (Aristida oligantha), in an
intermediate seral stage [10,91].  In tallgrass sand prairie, western
ragweed was present in pioneer stages, occurred with greatest frequency
in an intermediate phase, but had greatest cover in the climax phase
[25].  Although reported as a pioneer species, Cuman ragweed occurs on
secondary sand dunes but does not occur on less stable sites such as
primary dunes or tidal flats [27].  Additionally, Cuman ragweed occurs
outside of buffalo wallows, which are considered safe sites for ruderal
species [36].

Cuman ragweed may have allelopathic or other inhibitory effects on
other pioneer species.  Leachate from Cuman ragweed leaves and roots
significantly (P less than 0.05) reduced growth of soil bluegreen bacteria (Lyngby
spp.)  cultures [102].  While soil collected in July near western
ragweed was stimulatory to pioneer weedy species (for example, Japanese
brome [Bromus japonicus]), soil collected in January had an inhibitory
or no effect on seedlings of the same species [102].  Leaf leachate from
leaves that overwintered on Cuman ragweed plants inhibited
germination, seedling topgrowth, and mature plant root formation of the
pioneer species [102].

Ambrosia psilostachya var. psilostachya
Ambrosia psilostachya var. californica (Rydb.) Blake
Ambrosia psilostachya var. lindeheimerana (Scheele) Blank.
Ambrosia rugelii Rydb.
Ambrosia coronopifolia T. & G.

The currently accepted name of Cuman ragweed is Ambrosia psilostachya
DC.; it is a member of the sunflower family (Asteraceae)[51].

More info for the terms: forb, reclamation, restoration

Although Cuman ragweed readily invades disturbed ground and is not
considered desirable forage, it is a native forb and is included in
prairie restoration plantings.  Adequate seedbed preparation is
important for successful plant establishment [37,117].  Western ragweed
was seeded for tallgrass prairie restoration in north-central Missouri
at 0.08 pounds bulk per acre (91 g bulk/ha) with a rangeland drill
[117].  In the reclamation of a sand and gravel pit in Ohio, western
ragweed was hydroseeded with native grasses; seeds were covered with
less than 0.5 inch (1 cm) of soil [37].  Cuman ragweed has established
on artificial levees made to reclaim marshland along the lower
Sacramento River in California [127].

Established Cuman ragweed may have to be controlled when planting
other native species in an area.  For example, when fourwing saltbush
(Atriplex canescens) was planted on shrublands in Texas, Cuman ragweed
was controlled with herbicides [95].