SPECIES: Descurainia sophia

INTRODUCTORY

SPECIES: Descurainia sophia
   

photos by:

©Br. Alfred Brousseau, Saint Mary's College
USGS-NPA Vegetation Mapping Program

AUTHORSHIP AND CITATION:
Howard, Janet L. 2003. Descurainia sophia. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].

FEIS ABBREVIATION:
DESSOP

SYNONYMS:
None

NRCS PLANT CODE [138]:
DESO2

COMMON NAMES:
flixweed tansymustard
herb-sophia

TAXONOMY:
The scientific name of flixweed tansymustard is Descurainia sophia (L.) Webb ex Prantl (Brassicaceae) [32,48,51,64,69,90,106,130,133,142,145,147].

LIFE FORM:
Forb

FEDERAL LEGAL STATUS:
No special status

OTHER STATUS:
Flixweed tansymustard is classified as a noxious weed list in Colorado and Minnesota [137,138].

DISTRIBUTION AND OCCURRENCE

SPECIES: Descurainia sophia
GENERAL DISTRIBUTION:
Flixweed tansymustard is native to Europe and northern Africa [133]. It probably arrived in North America in the mid-1800s as an impurity in crop seed, and was widespread by the 1920s [103]. It now occurs in 48 states, excluding Alabama and Florida [72]. Its distribution extends south to Baja California, and as far north as 70o N latitude in Greenland, Alaska, and Canada. It occurs throughout Canada except Labrador and eastern Nunavut [69,72,133,147]. Plants database provides a distributional map of flixweed tansymustard in the United States and Canada. Flixweed tansymustard is also introduced in South America, Asia, southern Africa, and New Zealand [69,88].

The following biogeographic classification systems are presented as a guide to demonstrate where flixweed tansymustard may be found. Precise distribution information is limited. Because it is so widespread, it is difficult to exclude many ecosystems as potential hosts of flixweed tansymustard plants or populations; therefore, these lists are speculative.

ECOSYSTEMS [47]:
FRES10 White-red-jack pine
FRES11 Spruce-fir
FRES12 Longleaf-slash pine
FRES13 Loblolly-shortleaf pine
FRES14 Oak-pine
FRES15 Oak-hickory
FRES16 Oak-gum-cypress
FRES17 Elm-ash-cottonwood
FRES18 Maple-beech-birch
FRES19 Aspen-birch
FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES22 Western white pine
FRES23 Fir-spruce
FRES24 Hemlock-Sitka spruce
FRES25 Larch
FRES26 Lodgepole pine
FRES27 Redwood
FRES28 Western hardwoods
FRES29 Sagebrush
FRES30 Desert shrub
FRES31 Shinnery
FRES32 Texas savanna
FRES33 Southwestern shrubsteppe
FRES34 Chaparral-mountain shrub
FRES35 Pinyon-juniper
FRES36 Mountain grasslands
FRES37 Mountain meadows
FRES38 Plains grasslands
FRES39 Prairie
FRES40 Desert grasslands
FRES41 Wet grasslands
FRES42 Annual grasslands
FRES44 Alpine

STATES/PROVINCES: (key to state/province abbreviations)
UNITED STATES
AK AZ AR CA CO CT DE GA HI ID
IL IN IA KS KY LA ME MD MA MI
MN MS MO MT NE NV NH NJ NM NY
NC ND OH OK OR PA RI SC SD TN
TX UT VT VA WA WV WI WY DC PR
VI

CANADA
AB BC MB NB NF NT NS NU ON PE
PQ SK YK

MEXICO
B.C.N.

BLM PHYSIOGRAPHIC REGIONS [15]:
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

KUCHLER [78] PLANT ASSOCIATIONS:
K001 Spruce-cedar-hemlock forest
K002 Cedar-hemlock-Douglas-fir forest
K003 Silver fir-Douglas-fir forest
K004 Fir-hemlock forest
K005 Mixed conifer forest
K006 Redwood forest
K007 Red fir forest
K008 Lodgepole pine-subalpine forest
K009 Pine-cypress forest
K010 Ponderosa shrub forest
K011 Western ponderosa forest
K012 Douglas-fir forest
K013 Cedar-hemlock-pine forest
K014 Grand fir-Douglas-fir forest
K015 Western spruce-fir forest
K016 Eastern ponderosa forest
K017 Black Hills pine forest
K018 Pine-Douglas-fir forest
K019 Arizona pine forest
K020 Spruce-fir-Douglas-fir forest
K021 Southwestern spruce-fir forest
K022 Great Basin pine forest
K023 Juniper-pinyon woodland
K024 Juniper steppe woodland
K025 Alder-ash forest
K026 Oregon oakwoods
K027 Mesquite bosques
K028 Mosaic of K002 and K026
K029 California mixed evergreen forest
K030 California oakwoods
K031 Oak-juniper woodland
K032 Transition between K031 and K037
K033 Chaparral
K034 Montane chaparral
K035 Coastal sagebrush
K036 Mosaic of K030 and K035
K037 Mountain-mahogany-oak scrub
K038 Great Basin sagebrush
K039 Blackbrush
K040 Saltbush-greasewood
K041 Creosote bush
K042 Creosote bush-bur sage
K043 Paloverde-cactus shrub
K044 Creosote bush-tarbush
K045 Ceniza shrub
K046 Desert: vegetation largely lacking
K047 Fescue-oatgrass
K048 California steppe
K049 Tule marshes
K050 Fescue-wheatgrass
K051 Wheatgrass-bluegrass
K052 Alpine meadows and barren
K053 Grama-galleta steppe
K054 Grama-tobosa prairie
K055 Sagebrush steppe
K056 Wheatgrass-needlegrass shrubsteppe
K057 Galleta-threeawn shrubsteppe
K058 Grama-tobosa shrubsteppe
K059 Trans-Pecos shrub savanna
K060 Mesquite savanna
K061 Mesquite-acacia savanna
K062 Mesquite-live oak savanna
K063 Foothills prairie
K064 Grama-needlegrass-wheatgrass
K065 Grama-buffalo grass
K066 Wheatgrass-needlegrass
K067 Wheatgrass-bluestem-needlegrass
K068 Wheatgrass-grama-buffalo grass
K069 Bluestem-grama prairie
K070 Sandsage-bluestem prairie
K071 Shinnery
K072 Sea oats prairie
K073 Northern cordgrass prairie
K074 Bluestem prairie
K075 Nebraska Sandhills prairie
K076 Blackland prairie
K077 Bluestem-sacahuista prairie
K078 Southern cordgrass prairie
K079 Palmetto prairie
K080 Marl everglades
K081 Oak savanna
K082 Mosaic of K074 and K100
K083 Cedar glades
K084 Cross Timbers
K085 Mesquite-buffalo grass
K086 Juniper-oak savanna
K087 Mesquite-oak savanna
K088 Fayette prairie
K089 Black Belt
K090 Live oak-sea oats
K091 Cypress savanna
K092 Everglades
K093 Great Lakes spruce-fir forest
K094 Conifer bog
K095 Great Lakes pine forest
K096 Northeastern spruce-fir forest
K097 Southeastern spruce-fir forest
K098 Northern floodplain forest
K099 Maple-basswood forest
K100 Oak-hickory forest
K101 Elm-ash forest
K102 Beech-maple forest
K103 Mixed mesophytic forest
K104 Appalachian oak forest
K105 Mangrove
K106 Northern hardwoods
K107 Northern hardwoods-fir forest
K108 Northern hardwoods-spruce forest
K109 Transition between K104 and K106
K110 Northeastern oak-pine forest
K111 Oak-hickory-pine
K112 Southern mixed forest
K113 Southern floodplain forest
K114 Pocosin
K115 Sand pine scrub
K116 Subtropical pine forest

SAF COVER TYPES [41]:
1 Jack pine
5 Balsam fir
12 Black spruce
13 Black spruce-tamarack
14 Northern pin oak
15 Red pine
16 Aspen
17 Pin cherry
18 Paper birch
19 Gray birch-red maple
20 White pine-northern red oak-red maple
21 Eastern white pine
22 White pine-hemlock
23 Eastern hemlock
24 Hemlock-yellow birch
25 Sugar maple-beech-yellow birch
26 Sugar maple-basswood
27 Sugar maple
28 Black cherry-maple
30 Red spruce-yellow birch
31 Red spruce-sugar maple-beech
32 Red spruce
33 Red spruce-balsam fir
34 Red spruce-Fraser fir
35 Paper birch-red spruce-balsam fir
37 Northern white-cedar
38 Tamarack
39 Black ash-American elm-red maple
40 Post oak-blackjack oak
42 Bur oak
43 Bear oak
44 Chestnut oak
45 Pitch pine
46 Eastern redcedar
50 Black locust
51 White pine-chestnut oak
52 White oak-black oak-northern red oak
53 White oak
55 Northern red oak
57 Yellow-poplar
58 Yellow-poplar-eastern hemlock
59 Yellow-poplar-white oak-northern red oak
60 Beech-sugar maple
61 River birch-sycamore
62 Silver maple-American elm
63 Cottonwood
64 Sassafras-persimmon
65 Pin oak-sweetgum
66 Ashe juniper-redberry (Pinchot) juniper
67 Mohrs (shin) oak
68 Mesquite
69 Sand pine
70 Longleaf pine
71 Longleaf pine-scrub oak
72 Southern scrub oak
73 Southern redcedar
74 Cabbage palmetto
75 Shortleaf pine
76 Shortleaf pine-oak
78 Virginia pine-oak
79 Virginia pine
80 Loblolly pine-shortleaf pine
81 Loblolly pine
82 Loblolly pine-hardwood
83 Longleaf pine-slash pine
84 Slash pine
85 Slash pine-hardwood
87 Sweetgum-yellow-poplar
88 Willow oak-water oak-diamondleaf (laurel) oak
89 Live oak
91 Swamp chestnut oak-cherrybark oak
92 Sweetgum-willow oak
93 Sugarberry-American elm-green ash
94 Sycamore-sweetgum-American elm
95 Black willow
96 Overcup oak-water hickory
97 Atlantic white-cedar
98 Pond pine
100 Pondcypress
101 Baldcypress
102 Baldcypress-tupelo
103 Water tupelo-swamp tupelo
104 Sweetbay-swamp tupelo-redbay
105 Tropical hardwoods
106 Mangrove
107 White spruce
108 Red maple
109 Hawthorn
110 Black oak
111 South Florida slash pine
201 White spruce
202 White spruce-paper birch
203 Balsam poplar
204 Black spruce
205 Mountain hemlock
206 Engelmann spruce-subalpine fir
207 Red fir
208 Whitebark pine
209 Bristlecone pine
210 Interior Douglas-fir
211 White fir
212 Western larch
213 Grand fir
215 Western white pine
216 Blue spruce
217 Aspen
218 Lodgepole pine
219 Limber pine
220 Rocky Mountain juniper
221 Red alder
222 Black cottonwood-willow
223 Sitka spruce
224 Western hemlock
225 Western hemlock-Sitka spruce
226 Coastal true fir-hemlock
227 Western redcedar-western hemlock
228 Western redcedar
229 Pacific Douglas-fir
230 Douglas-fir-western hemlock
231 Port-Orford-cedar
232 Redwood
233 Oregon white oak
234 Douglas-fir-tanoak-Pacific madrone
235 Cottonwood-willow
236 Bur oak
237 Interior ponderosa pine
238 Western juniper
239 Pinyon-juniper
240 Arizona cypress
241 Western live oak
242 Mesquite
243 Sierra Nevada mixed conifer
244 Pacific ponderosa pine-Douglas-fir
245 Pacific ponderosa pine
246 California black oak
247 Jeffrey pine
248 Knobcone pine
249 Canyon live oak
250 Blue oak-foothills pine
251 White spruce-aspen
252 Paper birch
253 Black spruce-white spruce
254 Black spruce-paper birch
255 California coast live oak
256 California mixed subalpine

SRM (RANGELAND) COVER TYPES [120]:
101 Bluebunch wheatgrass
102 Idaho fescue
103 Green fescue
104 Antelope bitterbrush-bluebunch wheatgrass
105 Antelope bitterbrush-Idaho fescue
106 Bluegrass scabland
107 Western juniper/big sagebrush/bluebunch wheatgrass
108 Alpine Idaho fescue
109 Ponderosa pine shrubland
110 Ponderosa pine-grassland
201 Blue oak woodland
202 Coast live oak woodland
203 Riparian woodland
204 North coastal shrub
205 Coastal sage shrub
206 Chamise chaparral
207 Scrub oak mixed chaparral
208 Ceanothus mixed chaparral
209 Montane shrubland
210 Bitterbrush
211 Creosote bush scrub
212 Blackbush
213 Alpine grassland
214 Coastal prairie
215 Valley grassland
216 Montane meadows
217 Wetlands
301 Bluebunch wheatgrass-blue grama
302 Bluebunch wheatgrass-Sandberg bluegrass
303 Bluebunch wheatgrass-western wheatgrass
304 Idaho fescue-bluebunch wheatgrass
305 Idaho fescue-Richardson needlegrass
306 Idaho fescue-slender wheatgrass
307 Idaho fescue-threadleaf sedge
308 Idaho fescue-tufted hairgrass
309 Idaho fescue-western wheatgrass
310 Needle-and-thread-blue grama
311 Rough fescue-bluebunch wheatgrass
312 Rough fescue-Idaho fescue
313 Tufted hairgrass-sedge
314 Big sagebrush-bluebunch wheatgrass
315 Big sagebrush-Idaho fescue
316 Big sagebrush-rough fescue
317 Bitterbrush-bluebunch wheatgrass
318 Bitterbrush-Idaho fescue
319 Bitterbrush-rough fescue
320 Black sagebrush-bluebunch wheatgrass
321 Black sagebrush-Idaho fescue
322 Curlleaf mountain-mahogany-bluebunch wheatgrass
323 Shrubby cinquefoil-rough fescue
324 Threetip sagebrush-Idaho fescue
401 Basin big sagebrush
402 Mountain big sagebrush
403 Wyoming big sagebrush
404 Threetip sagebrush
405 Black sagebrush
406 Low sagebrush
407 Stiff sagebrush
408 Other sagebrush types
409 Tall forb
410 Alpine rangeland
411 Aspen woodland
412 Juniper-pinyon woodland
413 Gambel oak
414 Salt desert shrub
415 Curlleaf mountain-mahogany
416 True mountain-mahogany
417 Littleleaf mountain-mahogany
418 Bigtooth maple
419 Bittercherry
420 Snowbrush
421 Chokecherry-serviceberry-rose
422 Riparian
501 Saltbush-greasewood
502 Grama-galleta
503 Arizona chaparral
504 Juniper-pinyon pine woodland
505 Grama-tobosa shrub
506 Creosotebush-bursage
507 Palo verde-cactus
508 Creosotebush-tarbush
509 Transition between oak-juniper woodland and mahogany-oak association
601 Bluestem prairie
602 Bluestem-prairie sandreed
603 Prairie sandreed-needlegrass
604 Bluestem-grama prairie
605 Sandsage prairie
606 Wheatgrass-bluestem-needlegrass
607 Wheatgrass-needlegrass
608 Wheatgrass-grama-needlegrass
609 Wheatgrass-grama
610 Wheatgrass
611 Blue grama-buffalo grass
612 Sagebrush-grass
613 Fescue grassland
614 Crested wheatgrass
615 Wheatgrass-saltgrass-grama
701 Alkali sacaton-tobosagrass
702 Black grama-alkali sacaton
703 Black grama-sideoats grama
704 Blue grama-western wheatgrass
705 Blue grama-galleta
706 Blue grama-sideoats grama
707 Blue grama-sideoats grama-black grama
708 Bluestem-dropseed
709 Bluestem-grama
710 Bluestem prairie
711 Bluestem-sacahuista prairie
712 Galleta-alkali sacaton
713 Grama-muhly-threeawn
714 Grama-bluestem
715 Grama-buffalo grass
716 Grama-feathergrass
717 Little bluestem-Indiangrass-Texas wintergrass
718 Mesquite-grama
719 Mesquite-liveoak-seacoast bluestem
720 Sand bluestem-little bluestem (dunes)
721 Sand bluestem-little bluestem (plains)
722 Sand sagebrush-mixed prairie
723 Sea oats
724 Sideoats grama-New Mexico feathergrass-winterfat
725 Vine mesquite-alkali sacaton
726 Cordgrass
727 Mesquite-buffalo grass
728 Mesquite-granjeno-acacia
729 Mesquite
730 Sand shinnery oak
731 Cross timbers-Oklahoma
732 Cross timbers-Texas (little bluestem-post oak)
733 Juniper-oak
734 Mesquite-oak
735 Sideoats grama-sumac-juniper
801 Savanna
802 Missouri prairie
803 Missouri glades
804 Tall fescue
805 Riparian
806 Gulf Coast salt marsh
807 Gulf Coast fresh marsh
808 Sand pine scrub
809 Mixed hardwood and pine
810 Longleaf pine-turkey oak hills
811 South Florida flatwoods
812 North Florida flatwoods
813 Cutthroat seeps
814 Cabbage palm flatwoods
815 Upland hardwood hammocks
816 Cabbage palm hammocks
817 Oak hammocks
818 Florida salt marsh
819 Freshwater marsh and ponds
820 Everglades flatwoods
821 Pitcher plant bogs
822 Slough
ALASKA RANGELANDS
901 Alder
902 Alpine herb
903 Beach wildrye-mixed forb
904 Black spruce-lichen
905 Bluejoint reedgrass
906 Broadleaf forest
908 Fescue
910 Hairgrass
912 Low scrub shrub birch-ericaceous
915 Mixed herb-herbaceous
917 Tall shrub swamp
918 Tussock tundra
920 White spruce-paper birch
921 Willow

HABITAT TYPES AND PLANT COMMUNITIES:
Flixweed tansymustard grows in a broad spectrum of environments ranging from cold desert, tundra, taiga, alpine, and subalpine ecosystems to hot desert and dry-tropical Hawaiian ecosystems [72].

Flixweed tansymustard is ecologically important in most North American desert ecosystems. In Great Basin Desert communities of east-central Nevada, it showed 25-40% frequency in big sagebrush (Artemisia tridentata) communities and 5-66% frequency in singleleaf pinyon-Utah juniper (Pinus monophylla-Juniperus osteosperma) communities [18]. On the Desert Tortoise Research Natural Area in the Mojave Desert, southern California, flixweed tansymustard associates with creosotebush (Larrea tridentata), white bursage (Ambrosia dumosa), and other annuals, the most common being cutleaf filaree (Erodium cicutarium), red brome (Bromus madritensis ssp. rubens), and Mediterranean grass (Schismus spp.) [20].

A few vegetation classifications describe plant communities dominated by flixweed tansymustard.  A flixweed tansymustard-Russian-thistle (Salsola kali) community occurs in Lava Beds National Monument, California, on land with a history of extreme disturbance: 1st by lake drainage, then by cultivation of the lakebed [36]. In east-central Nevada, flixweed tansymustard communities occur on highly disturbed winterfat (Krascheninnikovia lanata) habitat types. Halogeton (Halogeton glomerata) codominates, and winterfat is present in trace amounts [18].


BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Descurainia sophia
GENERAL BOTANICAL CHARACTERISTICS:
The following description of flixweed tansymustard provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g. [32,48,51,64,106]).

Flixweed tansymustard is an exotic, cool-season annual or biennial. It is the type species for the genus [51,64,88,130,134]. The single, 6- to 31-inch-long (15-80 cm) stem is coarse, with basal and cauline leaves. Cauline leaves have a large amount of surface area, being 2 or 3 times pinnately divided. The inflorescence is a raceme of bisexual flowers. The fruit is a 1 × 10- to 71-mm-long silique bearing 10 to 20 small (10-25 mm long), seeds [32,49,51,64,96,106,145]. Tansymustard (Descurainia spp.) fruits and seeds do not have specialized appendages for dispersal [74,76]. Tansymustards have a short taproot [29,153].

Stand structure of flixweed tansymustard-dominated communities is sparse immediately after disturbance. Flixweed tansymustard stands often become dense and crowded within a few postdisturbance years, and thin as succession advances [16]. For further information on flixweed tansymustard's role in succession, see Successional Status below.

RAUNKIAER [107] LIFE FORM:
Therophyte

REGENERATION PROCESSES:
Flixweed tansymustard reproduces solely from seed [114,126].

Breeding system: Mustards (Brassicaceae) are cross-pollinated. Selfing also occurs [63].

Pollination is insect-mediated. The sepals contain nectaries that attract insect pollinators [63].

Seed production: Flixweed tansymustard produces an average of 75-650 seeds per plant [124]. A large plant may produce upwards of 700,000 seeds [114].

Seed dispersal: Wind, water, machinery, and animals transport flixweed tansymustard seed, although most seed falls near the parent plant [114]. Animals disperse tansymustard seeds when the mucilaginous seedcoat sticks to feathers or fur [155].

Seed banking: Flixweed tansymustard builds up a soil seed bank [2,5,39,149]. The seed bank can be large: Stevens [126] documented a flixweed tansymustard seed population of 704,582/m2 in North Dakota soil. Flixweed tansymustard was an important component of the soil seed pool (all spp.) in big sagebrush-green rabbitbrush (Chrysothamnus viscidiflorus) of southwestern Wyoming [30]. On the Nevada Test Site near Las Vegas, flixweed tansymustard was the 2nd most common species to emerge on irrigated and unirrigated test plots; red brome was most common [149]. Long-term viability of flixweed tansymustard seed is unknown, but the seed is reported to remain viable for "considerable periods in the soil" [114]. Buried flixweed seed remained viable at least 4 years in Fairbanks, Alaska. Seed viability generally dropped with years of soil storage [26]:

0 years 2.7 years 3.7 years 4.7 years
67% 28% 36% 10%

Germination: Flixweed tansymustard shows good germination [27], with a mean rate of about 70% [114]. Seed collected in Alberta showed 75% germination after cold storage/stratification. In another aspect of the study, some seeds from the lot survived digestion by ruminant grazers or short-term silage. Three percent of ingested seed germinated after 1 day in a cow's rumen, and seed stored in the bottom of a barley (Hordeum vulgare)-filled silo for 8 weeks showed 2% germination [19].

Flixweed tansymustard is adapted to establishing in dry environments. The seedcoat of tansymustards forms a thin layer of mucilage after wetting [64,155]; the mucilaginous layer helps germinating seeds retain water [155].

Seedling establishment/growth: The taproot exploits moisture in the upper soil layer [29,152,153], and uncrowded plants develop rapidly. Plants may develop numerous leaves and up to 15 lateral, fruit-bearing branches at maturity [16].

SITE CHARACTERISTICS:
Flixweed tansymustard occurs in open-canopy, disturbed sites. It is particularly common in washes and on roadsides, railroad rights-of-way, waste grounds, old fields, and early seral burns [35,64,70,100,101,110,142,151]. It grows in a variety of mineral soils including loam, silty clay [36], and sand, where it is most common. It tolerates dry soil, but is not salt tolerant [56,121]. In salt-desert shrubland of central Utah, flixweed tansymustard occurred only on plots with < 3,000 ppm soluble salts and < 12% soil moisture [121].

Elevational ranges of flixweed tansymustard are:

California <8,530 ft (<2,600 m) [64]
Colorado 4,000-8,000 ft (1,200-2,400 m) [57]
New Mexico 4,000-8,000 ft [82]
Nevada 2,220-9,000 ft (680-2,700 m) [73]
Utah 2,300-8,050 ft (700-2,450 m) [145]

SUCCESSIONAL STATUS:
Flixweed tansymustard occurs in early seral communities. It is common on disturbed ground [36,39,60,61,95,128,136]. For example, in a big sagebrush community in northwestern Colorado, flixweed tansymustard appeared the 1st year after bulldozing, showing mean productivity of 1 g/m2. Productivity peaked at postdisturbance year 2, and declined for the next 5 years. Flixweed tansymustard was present in only trace amounts on undisturbed control plots. It showed the same pattern of succession on plots that were fertilized with nitrogen after bulldozing, except productivity was greater on fertilized plots compared to unfertilized plots (15 vs. 5 g/m2 at postdisturbance year 2) [84]. On oilfields of Prudhoe Bay, Alaska, flixweed tansymustard was among the most important forbs 5 to 8 years after exploratory drilling [83]. Flixweed tansymustard is nonmycorrhizal [98]; thus, it is able to pioneer on sterile sites or on sites undergoing primary succession [3,17].

A common pattern of succession in disturbed sagebrush steppe begins with Russian-thistle. Flixweed tansymustard, pinnate tansymustard, and/or tumblemustard (Sisymbrium altissimum) soon follow successionally. Russian-thistle may in turn reinvade the mustard stands with grazing disturbance, but more commonly, the mustards are succeeded by cheatgrass (Bromus tectorum) [66,101,152]. In desert environments, cheatgrass usually requires litter for successful germination and establishment. Dried skeletons of flixweed tansymustard and other annual forbs may facilitate cheatgrass establishment by providing litter [37,38]. For information on the interactions of flixweed tansymustard and cheatgrass, see Fire Management Considerations and the FEIS review on cheatgrass.

Flixweed tansymustard is uncommon to absent in late seres [115]. In central Saskatchewan, flixweed tansymustard occurred in fallow and recently harvested wheat (Triticum aestivum) fields. It was not present, or found in seed bank soil samples, of adjacent undisturbed shortbristle need-and-thread-western wheatgrass (Hesperostipa curtiseta-Pascopyrum smithii) prairie [5]. On strip-mined sites in south-central Alaska, flixweed tansymustard volunteered on revegetated reclamation sites, but was absent by posttreatment year 10 [34]. Flixweed tansymustard is most likely to persist in communities that retain unlittered soil and open canopies into late succession. In singleleaf pinyon-Colorado pinyon (Pinus edulis)-Utah juniper communities of west-central Utah, where litter build-up can be slow, flixweed tansymustard occurred on burns in early to late stages of succession (3-100+ years), but was most common on new burns [13]. On mixed-grass prairies in Wyoming, which are likely to build up litter quickly, flixweed tansymustard was common for ~10 years postdisturbance, then became increasing scarce [115].

Flixweed tansymustard and the native pinnate tansymustard are apparently equally invasive, and fill similar ecological niches [89].

SEASONAL DEVELOPMENT:
Germination usually begins in winter or early spring [134,135], depending upon latitude and elevation. Flixweed tansymustard is 1 of the 1st plants to appear in spring. After the cotyledon stage, the seedling forms a rosette of basal leaves, then grows the stem and cauline leaves [64]. Fall-germinating seeds overwinter as rosettes [16]. In the United States, flixweed tansymustard 1st flowers in the Southeast [106,130]. Phenological events by region are:

Region Event Period
Southeast anthesis Feb.-Aug. [106,130]
Southwest anthesis March-July [73]
Pacific Northwest anthesis March-July [67]
Northeast anthesis May-July [48]
Great Plains anthesis northern: mid-June-late July [49,96]
southern: March-Sept. [32]
Great Lakes anthesis June-Aug. [90]
fruits ripen June-early Sept.  [96]

Flixweed tansymustard 1st sheds pollen in mid-May in North Dakota. Average flowering date is May 28th, with flowering ranging from mid-May to early June [125]. Over an 8-year period in western North Dakota, flixweed tansymustard began 1st bloom from mid-June to late July. Mean total growth was completed in June [49]. Similarly, May 30th was the mean flowering date over a 7-year period in Saskatchewan. Across years, flowering extended from mid-May to late July [22].

Fruits ripen in summer or early fall, and plants begin to dry out and die at that time. Fruits burst and disperse seed as the plant dries [152,153].

FIRE ECOLOGY

SPECIES: Descurainia sophia
FIRE ECOLOGY OR ADAPTATIONS:
Fire adaptations: Flixweed tansymustard establishes from soil-stored seed after fire [2,39]. Animal, wind, or machinery transport from off-site may provide additional, minor sources of seed [155] or introduce flixweed tansymustard to burns where it is not already present in the soil seed bank. Fire creates conditions favorable for flixweed tansymustard establishment (bare soil, open canopy, reduced growth interference) [16,101]. As a shade-intolerant, invasive species, flixweed tansymustard thrives in the early postfire environment [151].

Fire regimes: Introduced species can alter the rate of spread of fire, the probability of occurrence of fire, and the intensity of fire in an ecosystem [31]. Flixweed tansymustard has multiple, finely divided leaves [32,51,64,106] and tends to form dense stands that are dead and dry by the fire season [16]; hence, it provides a source of fine surface fuels that can spread fire. If flixweed tansymustard stands do not burn, they provide litter that favors establishment of species, including cheatgrass, which are more sensitive to desiccation as germinants and seedlings than flixweed tansymustard [37,38].

Flixweed tansymustard was absent or unimportant in fire-prone ecosystems when historic fire regimes were functional; however, pinnate and other tansymustards were present. Flixweed and pinnate tansymustard are morphologically and ecologically similar [89], and flixweed tansymustard is filling or sharing the ecological niche of pinnate tansymustard as an initial colonizer and early seral species on burns. The role of both species in facilitating establishment of other weedy species in dry environments by providing litter (and subsequently, more mesic conditions for germination and seedling growth of other species including cheatgrass) needs further investigation. There may be subtle differences in the effectiveness of the 2 species in facilitating postdisturbance succession; this also bears investigation, particularly in areas vulnerable to cheatgrass invasion.

Because flixweed tansymustard is widespread, it is difficult to exclude many ecosystems as potential hosts of flixweed tansymustard plants or populations. The following table provides some fire regime intervals for plant communities where flixweed tansymustard may be important. For further information, see the FEIS summary on the dominant species listed below.

Community or Ecosystem Dominant Species Fire Return Interval Range (years)
silver fir-Douglas-fir Abies amabilis-Pseudotsuga menziesii var. menziesii > 200
grand fir A. grandis 35-200 [8]
maple-beech-birch Acer-Fagus-Betula > 1000
silver maple-American elm A. saccharinum-Ulmus americana < 35 to 200
sugar maple A. saccharum > 1,000
sugar maple-basswood A. saccharum-Tilia americana > 1,000 [144]
California chaparral Adenostoma and/or Arctostaphylos spp. < 35 to < 100 [97]
bluestem prairie Andropogon gerardii var. gerardii-Schizachyrium scoparium < 10 [77,97]
Nebraska sandhills prairie A. gerardii var. paucipilus-S. scoparium < 10
bluestem-Sacahuista prairie A. littoralis-Spartina spartinae < 10 [97]
silver sagebrush steppe Artemisia cana 5-45 [62,104,150]
sagebrush steppe A. tridentata/Pseudoroegneria spicata 20-70 [97]
basin big sagebrush A. tridentata var. tridentata 12-43 [116]
mountain big sagebrush A. tridentata var. vaseyana 15-40 [9,23,87]
Wyoming big sagebrush A. tridentata var. wyomingensis 10-70 (40**) [141,156]
coastal sagebrush A. californica < 35 to < 100
saltbush-greasewood Atriplex confertifolia-Sarcobatus vermiculatus < 35 to < 100
desert grasslands Bouteloua eriopoda and/or Pleuraphis mutica 5-100 [97]
plains grasslands Bouteloua spp. < 35 [97,150]
blue grama-needle-and-thread grass-western wheatgrass B. gracilis-Hesperostipa comata-Pascopyrum smithii < 35 [97,113,150]
blue grama-buffalo grass B. gracilis-Buchloe dactyloides < 35 [97,150]
grama-galleta steppe Bouteloua gracilis-Pleuraphis jamesii < 35 to < 100
blue grama-tobosa prairie B. gracilis-P. mutica < 35 to < 100
cheatgrass Bromus tectorum < 10
California montane chaparral Ceanothus and/or Arctostaphylos spp. 50-100 [97]
sugarberry-America elm-green ash Celtis laevigata-Ulmus americana-Fraxinus pennsylvanica < 35 to 200 [144]
paloverde-cactus shrub Cercidium microphyllum/Opuntia spp. < 35 to < 100 [97]
curlleaf mountain-mahogany* Cercocarpus ledifolius 13-1000 [11,118]
mountain-mahogany-Gambel oak scrub C. ledifolius-Quercus gambelii < 35 to < 100 [97]
Atlantic white-cedar Chamaecyparis thyoides 35 to > 200 [144]
blackbrush Coleogyne ramosissima < 35 to < 100
Arizona cypress Cupressus arizonica < 35 to 200
northern cordgrass prairie Distichlis spicata-Spartina spp. 1-3 [97]
beech-sugar maple Fagus spp.-Acer saccharum > 1000 [144]
California steppe Festuca-Danthonia spp. < 35 [97,129]
black ash Fraxinus nigra < 35 to 200 [144]
juniper-oak savanna Juniperus ashei-Quercus virginiana < 35
Ashe juniper J. ashei < 35
western juniper J. occidentalis 20-70
Rocky Mountain juniper J. scopulorum < 35
cedar glades J. virginiana 3-7
tamarack Larix laricina 35-200 [97]
western larch L. occidentalis 25-100 [8]
creosotebush Larrea tridentata < 35 to < 100
Ceniza shrub L. tridentata-Leucophyllum frutescens-Prosopis glandulosa < 35 [97]
yellow-poplar Liriodendron tulipifera < 35 [144]
wheatgrass plains grasslands Pascopyrum smithii < 5-47+ [97,104,150]
Great Lakes spruce-fir Picea-Abies spp. 35 to > 200
northeastern spruce-fir Picea-Abies spp. 35-200 [33]
southeastern spruce-fir Picea-Abies spp. 35 to > 200 [144]
Engelmann spruce-subalpine fir P. engelmannii-A. lasiocarpa 35 to > 200 [8]
black spruce P. mariana 35-200 [33]
blue spruce* P. pungens 35-200 [8]
red spruce* P. rubens 35-200 [33]
pine-cypress forest Pinus-Cupressus spp. < 35 to 200 [8]
pinyon-juniper Pinus-Juniperus spp. < 35 [97]
whitebark pine* P. albicaulis 50-200 [1,6]
jack pine P. banksiana <35 to 200 [33]
Mexican pinyon P. cembroides 20-70 [91,132]
Rocky Mountain lodgepole pine* P. contorta var. latifolia 25-300+ [7,8,112]
Sierra lodgepole pine* P. contorta var. murrayana 35-200 [7]
shortleaf pine P. echinata 2-15
shortleaf pine-oak P. echinata-Quercus spp. < 10 [144]
Colorado pinyon P. edulis 10-400+ [44,50,75,97]
slash pine P. elliottii 3-8
slash pine-hardwood P. elliottii-variable < 35
sand pine P. elliottii var. elliottii 25-45 [144]
Jeffrey pine P. jeffreyi 5-30
western white pine* P. monticola 50-200 [8]
longleaf-slash pine P. palustris-P. elliottii 1-4 [94,144]
longleaf pine-scrub oak P. palustris-Quercus spp. 6-10 [144]
Pacific ponderosa pine* P. ponderosa var. ponderosa 1-47 [8]
interior ponderosa pine* P. ponderosa var. scopulorum 2-30 [8,12,80]
Arizona pine P. ponderosa var. arizonica 2-15 [12,28,119]
Table Mountain pine P. pungens < 35 to 200 [144]
red pine (Great Lakes region) P. resinosa 10-200 (10**) [33,46]
red-white-jack pine* P. resinosa-P. strobus-P. banksiana 10-300 [33,58]
pitch pine P. rigida 6-25 [21,59]
pocosin P. serotina 3-8
pond pine P. serotina 3-8
eastern white pine P. strobus 35-200
eastern white pine-eastern hemlock P. strobus-Tsuga canadensis 35-200
eastern white pine-northern red oak-red maple P. strobus-Quercus rubra-Acer rubrum 35-200
loblolly pine P. taeda 3-8
loblolly-shortleaf pine P. taeda-P. echinata 10 to < 35
Virginia pine P. virginiana 10 to < 35
Virginia pine-oak P. virginiana-Quercus spp. 10 to < 35
sycamore-sweetgum-American elm Platanus occidentalis-Liquidambar styraciflua-Ulmus americana < 35 to 200 [144]
galleta-threeawn shrubsteppe Pleuraphis jamesii-Aristida purpurea < 35 to < 100
eastern cottonwood Populus deltoides < 35 to 200 [97]
aspen-birch P. tremuloides-Betula papyrifera 35-200 [33,144]
quaking aspen (west of the Great Plains) P. tremuloides 7-120 [8,55,86]
mesquite Prosopis glandulosa < 35 to < 100 [85,97]
mesquite-buffalo grass P. glandulosa-Buchloe dactyloides < 35
Texas savanna P. glandulosa var. glandulosa < 10 [97]
black cherry-sugar maple Prunus serotina-Acer saccharum > 1000 [144]
mountain grasslands Pseudoroegneria spicata 3-40 (10**) [7,8]
Rocky Mountain Douglas-fir* Pseudotsuga menziesii var. glauca 25-100 [8,9,10]
coastal Douglas-fir* P. menziesii var. menziesii 40-240 [8,92,109]
California mixed evergreen P. menziesii var. m.-Lithocarpus densiflorus-Arbutus menziesii < 35
California oakwoods Quercus spp. < 35 [8]
oak-hickory Quercus-Carya spp. < 35[144]
oak-juniper woodland (Southwest) Quercus-Juniperus spp. < 35 to < 200 [97]
northeastern oak-pine Quercus-Pinus spp. 10 to < 35 [144]
oak-gum-cypress Quercus-Nyssa-spp.-Taxodium distichum 35 to > 200 [94]
southeastern oak-pine Quercus-Pinus spp. < 10 [144]
coast live oak Q. agrifolia 2-75 [52]
white oak-black oak-northern red oak Q. alba-Q. velutina-Q. rubra < 35 [144]
canyon live oak Q. chrysolepis <35 to 200
blue oak-foothills pine Q. douglasii-Pinus sabiniana <35 [8]
northern pin oak Q. ellipsoidalis < 35 [144]
Oregon white oak Q. garryana < 35 [8]
bear oak Q. ilicifolia < 35 >[144]
California black oak Q. kelloggii 5-30 [97]
bur oak Q. macrocarpa < 10 [144]
oak savanna Q. macrocarpa/Andropogon gerardii-Schizachyrium scoparium 2-14 [97,144]
shinnery Q. mohriana < 35 [97]
chestnut oak Q. prinus 3-8
northern red oak Q. rubra 10 to < 35
post oak-blackjack oak Q. stellata-Q. marilandica < 10
black oak Q. velutina < 35
live oak Q. virginiana 10 to< 100 [144]
interior live oak Q. wislizenii < 35 [8]
cabbage palmetto-slash pine Sabal palmetto-Pinus elliottii < 10 [94,144]
blackland prairie Schizachyrium scoparium-Nassella leucotricha < 10
Fayette prairie S. scoparium-Buchloe dactyloides < 10
little bluestem-grama prairie S. scoparium-Bouteloua spp. < 35
tule marshes Scirpus and/or Typha spp. < 35 [144]
redwood Sequoia sempervirens 5-200 [8,42,131]
southern cordgrass prairie Spartina alterniflora 1-3 [97]
baldcypress Taxodium distichum var. distichum 100 to > 300
pondcypress T. distichum var. nutans < 35 [94]
western redcedar-western hemlock Thuja plicata-Tsuga heterophylla > 200 [8]
eastern hemlock-yellow birch T. canadensis-Betula alleghaniensis > 200 [144]
western hemlock-Sitka spruce T. heterophylla-Picea sitchensis > 200
mountain hemlock* T. mertensiana 35 to > 200 [8]
elm-ash-cottonwood Ulmus-Fraxinus-Populus spp. < 35 to 200 [33,144]
*fire return interval varies widely; trends in variation are noted in the species summary
**mean

POSTFIRE REGENERATION STRATEGY [127]:
Ground residual colonizer (on-site, initial community)
Initial off-site colonizer (off-site, initial community)

FIRE EFFECTS

SPECIES: Descurainia sophia
IMMEDIATE FIRE EFFECT ON PLANT:
While in the rosette stage, flixweed tansymustard may be top-killed by fire. If the root crown is not damaged, flixweed tansymustard rosettes can sprout  new basal leaves from the root crown. As an annual with a single stem, flixweed tansymustard lacks adaptations for regrowth once it has bolted [2,39], and plants burned after the rosette stage are killed. Research on fire's impact to the seed bank is lacking as of this writing (2003), but it appears that fire has little effect on flixweed tansymustard seed populations. Flixweed tansymustard has tiny seeds [32,51,64,106] that easily fall into fire-safe microsites such as soil crevices. While fire is likely to kill some seed, its overall effect to the flixweed tansymustard seed bank is probably negligible.

DISCUSSION AND QUALIFICATION OF FIRE EFFECT:
No entry

PLANT RESPONSE TO FIRE:
Flixweed tansymustard establishes from soil-stored seed after fire [2,39], reaching greatest density in early postfire succession [13,95]. Banked seed usually germinates and establishes in postfire years 1 or 2. The postfire population increases rapidly, and by postfire years 2 to 4, localized, dense stands of flixweed tansymustard may form [13,39]. In pinyon-juniper (Pinus-Juniperus spp.) stands of Nevada and Utah, for example, flixweed tansymustard appears in early successional years along with other annual herbs [13,102]. Flixweed tansymustard density decreases as postfire succession continues, although flixweed tansymustard may persist in low numbers in late-successional burns that have retained an open canopy [13,14].

In big sagebrush communities that have experienced fire or other disturbance that removes the sagebrush, flixweed tansymustard commonly dominates or is an important component of the initial postfire community. Along with flixweed tansymustard, Russian-thistle, pinnate tansymustard, and/or tumblemustard form the initial plant community, which is dominated by annuals. Cheatgrass may be part of the initial community in mesic environments. On dry sites, it may follow successionally soon after the annual forbs [101], when litter has created a seedbed favorable for cheatgrass germination [37,38].

Although fire creates an open canopy and bare mineral soil, which favors flixweed tansymustard establishment, flixweed tansymustard is not an obligate "fire follower." Any area with bare ground, open sunlight, and a seed source is vulnerable to flixweed tansymustard invasion [60,61].

Grazing: Few studies have focused on the interactive effects of fire and grazing on flixweed tansymustard. One study suggests that fire and grazing may reduce postfire cover of annuals more than fire alone, but the results are inconclusive for flixweed tansymustard. Russian-thistle, flixweed tansymustard, and prickly-lettuce (Lactuca serriola) were the 3 most important annual forbs, respectively, on a Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis)-green rabbitbrush burn in central Utah. The 3 annual forbs showed greatest coverage on ungrazed, burned sites (~50%), slightly less cover on grazed, burned sites (~45%), and least cover on grazed, unburned sites (~27%). (Data are pooled means for the 3 forbs over 12 postfire years) [146]. Further studies are needed to understand how combined fire and grazing affect flixweed tansymustard.

DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
Flixweed tansymustard may invade after restoration treatments [34], including postfire restoration. It was the most abundant exotic forb species 1 and 2 years after prescribed burning and glyphosate treatment to control smooth brome (Bromus inermis) on native rough fescue (Festuca altaica) prairie in Saskatchewan. Flixweed tansymustard numbers were similar on smooth brome-infested and native prairie plots, which were also treated with fire and herbicide [53].

Burning may not increase postfire cover of flixweed tansymustard. In his classic study of postfire succession of flixweed tansymustard and other exotics in big sagebrush, Piemeisel  [100] wrote "the mere statement that a field has been burned is not sufficient information to foretell what the effect will be on the succeeding plant cover." For example, a Gambel oak/common snowberry (Symphoricarpos albus) community in Utah was chained and burned to increase forage production for cattle and elk. Two years after treatment, flixweed tansymustard cover showed little change (± 1%) compared to pretreatment levels [79]. Piemesel [100] stated that site grazing history, postfire weather patterns, and level of postfire cheatgrass cover will affect cover and relative abundance of flixweed tansymustard and other early successional forbs.

The Research Project Summary Nonnative annual grass fuels and fire in California's Mojave Desert provides information on prescribed fire and postfire response of plant community species including flixweed tansymustard.

FIRE MANAGEMENT CONSIDERATIONS:
Fire as a control agent: There are no published studies on using fire to control flixweed tansymustard, but given flixweed tansymustard's strong response to increased light and nutrients and open ground, fire alone is unlikely to provide control. If flixweed tansymustard is already onsite in the seed bank, or as a few plants, fire is likely to increase the species' importance in the early postfire community.

Interactions with cheatgrass: If present in the seed bank, flixweed tansymustard is liable to dominate early postfire communities if the seedbed or the postfire climate are unfavorable for cheatgrass establishment [37,38,100]. Even when cheatgrass dominates the postfire community, flixweed tansymustard is likely to be an important forb. The 2 species are frequently found together in the prefire seed bank. In a big sagebrush-rubber rabbitbrush (Chrysothamnus nauseosus) community in Wyoming, cheatgrass dominated the seed bank, but flixweed tansymustard was 1 of the most important forbs in the seed bank [93]. Succession after a July 1985 wildfire on the Snake River Birds of Prey Area, southwestern Idaho, followed a typical pattern, with flixweed tansymustard showing greater cover than any other plant species except cheatgrass. There was much open ground in the area, especially on sites prepared for postfire rehabilitation. Mean percent cover at postfire year 1 was [54]:

  Burned Partially burned Burned/rehabilitated* Unburned, untreated control
flixweed tansymustard 5 3 6 < 1
cheatgrass 26 9 14 5
bare ground 22 22 54 22
*drill-seeded with crested wheatgrass (Agropyron cristatum), yellow sweetclover (Melilotus officinalis), and fourwing
saltbush (
Atriplex canescens)

Interactions with pinnate and other tansymustards: Although they are taxonomically and ecologically similar, little is known of possible  growth interference of  exotic flixweed tansymustard to pinnate and other native tansymustards in postfire environments. Limited studies are inconclusive, and further research is needed in this area. A review by Wright and others [151] describes flixweed tansymustard as more resilient to fall prescribed burning than pinnate tansymustard ("undamaged" vs. "slightly damaged" by fall fire, respectively). Postfire responses of the 2 species probably depend upon their relative abundance in the prefire seed bank and poorly understood differences in germination and seedling establishment requirements. Floyd-Hanna and others [45] noted the presence of both species after the Chapin 5 Wildfire at Mesa Verde National Park in the summer of 1996. Flixweed tansymustard was more frequent on study plots than pinnate tansymustard at postfire year 1. Flixweed tansymustard was not observed on study plots at postfire year 2, while pinnate tansymustard increased. Tansymustard frequencies (%) on burn sites were as follows [45]:

  Flixweed tansymustard Pinnate tansymustard

1997

Gambel oak/Utah serviceberry* mountain shrubland 16  3
Gambel oak-Colorado pinyon-Utah juniper 12  1
Colorado pinyon-Utah juniper 10  2

1998

Gambel oak/Utah serviceberry mountain shrubland  0 31
Gambel oak-Colorado pinyon-Utah juniper  0 24
Colorado pinyon-Utah juniper  0 27
*Amelanchier utahensis

MANAGEMENT CONSIDERATIONS

SPECIES: Descurainia sophia
IMPORTANCE TO LIVESTOCK AND WILDLIFE:
Flixweed tansymustard is toxic to livestock, causing blindness, staggering, and loss of ability to swallow. All parts of the plant contain poisonous levels of nitrate [43,123]. The seeds contain poisonous isoallyl thiocyanates and irritant oils. Large quantities of the plant must be consumed for long periods of time for poisoning to occur [43].

Wildlife use of flixweed and other tansymustards is poorly documented, and further studies are needed to determine the relative importance of tansymustards in animal communities.

Small mammals: Townsend's ground squirrels graze tansymustards, sometimes in large quantity. Spring use of tansymustard has ranged from 3% on the Snake River Birds of Prey Area in southwestern Idaho to 33% in eastern Washington [71,111,154].

Birds: Sage-grouse in Nevada grazed most of the early spring forbs in a big sagebrush community, but avoided flixweed tansymustard [117]. In free-choice trials, chukar preferred pinnate tansymustard seeds to cheatgrass seeds, which form the main staple of their diet [155].

Flixweed tansymustard is a larval food for orangetip, white checkered, and white cabbage butterflies [68].

Palatability/nutritional value: Flixweed tansymustard is moderately palatable to livestock, although livestock may prefer other tansymustard species. In free-choice trials, cattle in Montana selected pinnate tansymustard more often than flixweed tansymustard [99].

Cover value: No information

OTHER USES:
Flixweed tansymustard seeds have a flavor similar to commercial black mustard (Brassica nigra) seeds, and are used as a spice [32]. The Navajo used ground flixweed tansymustard seeds in baked goods [140]. The stems and leaves are used as fiber in India [139]

IMPACTS AND CONTROL:
Impacts: The greatest impact of flixweed and other tansymustards to wildlands is probably their role in facilitating succession. See Successional Status for further information.

Flixweed tansymustard invades rangelands disturbed by heavy grazing [105]. It is a common volunteer on restoration and rehabilitation projects [122,143].

Flixweed tansymustard is a crop pest [89] and an alternate host for beet leafhoppers, which transmit curly top virus to sugar beet (Beta vulgaris) crops [65].

Control: Flixweed tansymustard does not usually persist in late-seral communities and may not require special control measures. Canopy closure, litter accumulation and/or growth interference from later-successional species tend to exclude tansymustard over time. For example, flixweed tansymustard volunteered between rough fescue sod patches on a restoration project in Alberta. As the rough fescue grew and litter accumulated, flixweed tansymustard became less abundant [108]. Perhaps because it is largely controlled by succession, there is scant wildland-management interest in using resource monies to control flixweed tansymustard with fire, herbicides, or other treatments.

Prevention/Cultural: Since flixweed tansymustard is an early seral species, minimizing soil disturbance and seed dispersal and maintaining a healthy plant community is the best way to prevent establishment of flixweed tansymustard [25].

Integrated management: Land management practices that promote later-successional species can exclude flixweed tansymustard from most plant communities [25]. Some communities, such as sagebrush steppe and salt-desert shrubland, maintain open light and bare ground conditions well into late succession [81]. For these communities, flixweed tansymustard is controlled by eliminating seed production until the seed bank is depleted. Mechanical treatment or herbicide application prior to seed set treats established plants [25]. Managers are encouraged to use combinations of control techniques that are appropriate to the site objectives, desired plant community, available resources, and timing of application. For information on integrated weed management without herbicides, see the Bio-Integral Resource Center (BIRC) website.

Physical/mechanical: Small infestations of flixweed tansymustard can be controlled by hand pulling rosettes in the fall or early spring [25].

Fire: See Fire Management Considerations.

Biological: There are no biological control organisms reported for flixweed tansymustard [25].

Chemical: Herbicides are effective in gaining initial control of a new invasion or a severe infestation, but are rarely a complete or long-term solution to weed management [24]. Herbicides are more effective on large infestations when incorporated into long-term management plans that include replacement of weeds with desirable species, careful land use management, and prevention of new infestations. Control with herbicides is temporary, as it does not change those conditions that allow infestations to occur [157]. See the Weed Control Methods Handbook for considerations on the use of herbicides in natural areas and detailed information on specific chemicals.

Flixweed tansymustard seedlings are sensitive to most herbicides at relatively low application rates. Glyphosate and 2,4-D give excellent control [135,148], as do many other herbicides [148]. Herbicide choice and rates are influenced by growth stage, stand density, and environmental conditions (e.g. drought or cold temperatures). Check with state or county weed specialists for appropriate local use rates and timing.

Descurainia sophia: References


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