Potentially Invasive Plant Species In Bidwell Park

Common Name Scientific Name		Listed? IPC CA BC	Blooming Period	Locations	Dispersal Agents	Photo Link	Control Method	Habitats / Comments
	Plants ranked #1 on park priority list: Highly invasive. Should have immediate management
	Algerian ivy Hedera canariensis	H	Mid-Sept	Lower and Middle Park	Vegetative, birds			Riparian, woodland, encroaching from neighboring residential properties
	American pokeweed Phytolacca americana	L	Early Jul-Oct.	Lower and Middle Park	Birds			Riparian; spreading rapidly in Bidwell Park, becoming a fairly common weed in the Chico Urban Area.
	Barbed goatgrass Aegilops triuncialis	H B	Early May	Upper Park 100′ east of start of Middle Trail by Lot A, Pine Trailhead, Guardian Trail by Pine Trail	wind		CDFA	Only a few infestations, should eradicate before it spreads
	Bladder senna Colutea arborescens		Late May-Jun.	Lower Park; Cedar Grove, Five Mile	human, gravity; indehiscent			Riparian, Valley Oak Woodland; Came from 1 plant in 1890s.  Control attempted in past, focused eradication program started by FOBP in May, 2003 with about 1M plants removed so far. People spread seeds by "popping" pods as they walk through the park.
	Broomsedge bluestem Andropogon virginicus		Early Sept.	Upper Park			GISD	Moist to wet soil along streams, on seeps, along ponds, in pastures. Native to eastern U.S., destroying park’s wetlands. CA native species in same area–needs careful ID before removal.
	Chinese tallowtree Sapium sebiferum	M		One Mile Way, between picnic 24-25	birds		TISI, TNC
	Edible fig Ficus carica	M   *	Late Mar.-Apr.	Lower, Middle and Upper Park	Birds, Mammals			Riparian, very large trees near old cabin site on Ten Mile House Rd and in former deer pen
	English ivy Hedera helix	H   *	Mid-Sept.	Lower and Middle Park	Vegetative, birds		No Ivy League	Riparian, Valley Oak Woodland; mature ivy encroaching from many South Park Drive neighbors
	French broom Genista monspessulana	H B	Late Mar.-Jul.	Middle Park by Hooker Oak Recreation Area	Gravity, Water			Riparian, Valley Oak, and Foothill Woodland; disturbed road edges;
	French tamarisk Tamarix ramoissima	H B	Early Apr.-May	One plant in Upper Park upstream of Day Camp, Lindo Channel	Wind		TISI, TNC	Riparian; dispersed by millions of dust-like seeds
	Giant reed, Arundo Arundo donax	H B *	Early Oct.	Lost Park, Lower and Middle Park, Lindo Channel	Spread by rhizomes moved during flooding		TISI, TNC	Riparian; control underway since 2000 by City of Chico; about 110 mapped sites, roots and rhizomes tenacious. Big Chico Creek Watershed Alliance eradication project in Lindo Channel and BCC upstream of Five Mile Dam 2005-2008 appears to have killed most of the remaining arundo–needs annual monitoring & possible respraying by Park staff.
	Himalayan blackberry Rubus armeniacus	H   *	Early May-June	Lower, Middle and Upper Park	Birds Mammals		TISI, TNC	Riparian-Valley Oak Woodland; can be confused with native blackberry, City of Chico has used burning, Salt Creek Crews & goats for control
	Italian plumeless thistle Carduus pycnocephalus	M C	Mid April-June	Guardian Trail, lower end of Yahi	wind, humans, animals		TISI, TNC	Grassland, Oak Woodland-three known populations–two on Guardian Trail by former BLM property, one on Yahi near start of trail
	Japanese privet Ligustrum japonicum	*	Late spring-early summer	Lost Park, Annie’s Glen, Camellia Way Park, Lower, Middle & Upper Park	Birds		TISI, TNC	Riparian, Valley Oak Woodland; Widely planted horticultural shrub, 264 mapped sites in park, eradication underway at Five Mile & in Lower Park. As of 2009, last major infestations at golf course, area east of Caper Acres and between Crister/Madrone near Vallombrosa Ave.
	Klamath weed, St. John’s wort Hypericum perforatum	M C	Late April-Oct	Lower, Middle and Upper Park				Grassland, Foothill Woodland
	Mediterranean hackberry Celtis australis		Apr.	Lower, Middle and Upper Park	Birds			May be the most prevalent hackberry species in Park.  Spreading rapidly from original 1900 plantings in Cedar Grove.  Major infestations on both sides of creek in this area.
	Medusahead grass Taeniatherum caput-medusae	H C	Late Mar.	Lower, Middle and Upper Park	Mammals		TISI, TNC	Annual Grassland; common grass in Upper Park; can be controlled with fire and grazing; some controlled burns done by City of Chico
	Olive Olea europaea	L	Late May-Jun.	Lower, Middle and Upper Park; old grove south of golf course	Birds			Riparian, Foothill Woodland; can form very dense canopies; spreading up canyon on both sides of creek, UC Davis research project may provide map of Upper Park locations
	Perennial pepperweed, tall whitetop Lepidium latifolium	H B *	Early May-Sept.	Lower Park	Wind, Water, Animals?		TISI, TNC	Riparian; roots can exceed 20 feet in depth, small infestation eradicated with herbicide at walnut orchard area in 2003, needs annual monitoring of area by park staff
	Periwinkle Vinca major	M   *	Mid Jan.-Jul.	Lower, Middle and Upper Park	Vegetative		TISI, TNC	Riparian, Valley Oak Woodland; forms dense sprawling mats that smother all other understory species; displaces California Grape, Native Blackberry, Pipevine, etc.
	Puncturevine Tribulus terrestris	C *	Early May-Oct.	Lower, Middle and Upper Park	Mammals (shoes and tires)			Disturbed road and trail margins; a painful nuisance to barefoot children, dogs, and troublesome to bicyclists, FOBP monitors/removes in Lower Park, Park contracts herbicide spraying along Upper Park Road
	Smooth hawthorn Crataegus laevigata		Mid Apr.	Lower, Middle & Upper Park				Need to confirm species.  Becoming prevalent in Lower and Middle Park from experimental plantings at the old Bidwell Forestry Station (now Cedar Grove) in Lower Park.  Difficult to eradicate due to root structure, large, thorny mass of woody debris to be removed
	Spanish broom Spartium junceum	H B *	Early Mar-Jul.	Upper Park	Gravity		TISI, TNC	Riparian, Valley Oak Woodland; Common and increasingly widespread on disturbed stream edges and along Hwy 32. Eradication efforts since 1995 by CNPS
	Tree of heaven Ailanthus altissima	M UC *	Late Apr.-May	Lost Park, Annie’s Glen, Lower and Middle Park	root sprouts, wind		TISI, TNC	Riparian, Valley Oak Woodland; Increasingly common and widespread tree, FOBP eradication effort since 2005, volunteer licensed herbicide applicator uses basal bark treatment of Garlon 4–very effective if used in late summer & fall
	Western Catalpa Catalpa speciosa		Early May	Lower and Middle Park	water			Riparian Woodland; FOBP mapped locations in 2007, will need permits to eradicate/revegetate by creek
	Yellow starthistle Centaurea solstitialis	H C *	Most months	Lower, Middle and Upper Park	Wind		TISI, TNC	Annual Grassland, openings in Woodland; abundant and widespread; can be controlled with fire and grazing
	Plants ranked #2 on park priority list: Moderately invasive. Should provide management when possible
	Black locust Robinia pseudoacacia	L	Mid April-May	Lower Park, Lost Park, Annie’s Glen, Upper Park by Green Gate	Gravity, water, animals?		TISI, TNC	Widely naturalized along streams on the valley floor and in the foothills; scattered in lower coniferous forest. Native to eastern U.S.
	Bouncingbet Saponaria officinalis	L	Late June-Oct	Upper Park
	Bull thistle Cirsium vulgare	M C	Most months	Upper Park	Wind			Riparian areas, marshes and meadows
	Bur-chervil Anthriscus caucalis		Early March-April	Lower, Middle and Upper Park	People and other animals			Should try to control in high-use areas and along trails
	Canada thistle Cirsium arvense	M B	Late Jul.-Sept.		Wind		GISD	Troublesome in riparian areas, need to verify that it’s in the park
	Cheat grass, Downy brome Bromus tectorum	H	Early May	Lower, Middle and Upper Park	Mammals, Wind		TISI, TNC	Annual Grassland
	Cork or rock elm Ulmus thomasii			Cedar Grove area				Very localized infestation–need to remove many of the smaller trees, girdling will leave areas of fire-prone dead 6-8′ trees
	Eastern or common hackberry Celtis occidentalis			Lower, Middle and Upper Park
	European privet Ligustrum vulgare		Early spring-early summer	Lower and Middle Park	Birds		TISI, TNC	Much less prevalent than Japanese privet.  According to literature, must remove most of root system to eradicate.
	Garden (Salad) burnet Sanguisorba minor muricata		May-August	Upstream end of Upper Park				Extensive root system, need to control to prevent spread from BCCER
	Italian arum Arum italicum		Early May	Lower Park	Vegetatively, corms moved by underground rodents			Very prevalent in One Mile area especially east of Caper Acres, difficult to eradicate
	Italian thistle Carduus tenuiflorus	*		Upper Park
	Johnsongrass Sorghum halepense		Late May	Lower and Upper Park	Rhizomes		TISI, TNC	Moist to dry fields, orchards, lawns, roadsides, waste places. Native to Mediterranean.
	Milk thistle Silybum marianum		Early March-June	Lower Park, Upper Park by Horseshoe Lake			TISI, TNC	Should try to eradicate in high-use areas
	Pampas grass Cortaderia selloana	H   *	Early Sept.	Lower and Middle Park	Wind		GISD	Riparian, Valley Oak Woodland; popular in landscaping , 2 patches at Five Mile, one along S. Park Dr., 2 locations on Vallombrosa Ave.
	Pennsylvania blackberry Rubus pensilvanicus		Mid May-July	Lower, Middle and Upper Park
	Pyracantha, Chinese firethorn Pyracantha angustifolia	L	Late May-Jun	Lower Park	Birds			Riparian, Valley Oak Woodland
	Red or foxtail brome Bromus madritensis ssp. rubens	H	Early June	Lower Park			TISI, TNC	Native to Australia
	Silver maple Acer saccharinum		Early Spring	Lower Park	Wind			Widely planted street and shade tree that volunteers along creeks and river. Native to eastern N. America.
	Tall fescue Festuca arundinacea	M	Mid-April	Upper Park			TISI, TNC	Grassland, Foothill Woodland
	Thornless (elmleaf) blackberry Rubus ulmifolius var inermis		Early May-June	Lower Park	Birds, vegetatively			Dense growth (about 30' x 150') at picnic site #8. Mentioned in Big Chico Creek Existing Conditions Report & Joe DiTomaso's Aquatic and Riparian Weeds of the West
	Tocalote, Malta starthistle Centaurea melitensis	M C	Late Mar.-Jul.	Upper Park	Wind, Mammals		GISD	Annual Grassland, Foothill Woodland; occasional weed; can be confused with Yellow Star Thistle; old plants can flower in the Fall and early Winter
	Tumbleweed, pigweed Amaranthus albus		Early May-Sept	Upper Park
	Woolly or common mullein Verbascum thapsus	L	Early Mar.-Oct.	Lower and Upper Park	Wind		TISI, TNC	Riparian and disturbed areas in Woodlands; common along road edges in the County
	Plants ranked #3 on park priority list: Low to moderately invasive. Should monitor.
	Almond prunus dulcis		Mid Feb-Aprilo	Lower and Middle Park	squirrels
	American elm Ulmus americana		Spring	Lower and Middle Park	Wind			Widely planted street tree. It volunteers freely along Big Chico Creek, particularly on the University campus, but so far has not been found outside the urban area. Native to eastern U.S.
	Black mustard Brassica nigra	M		Upper Park				Grassland, Foothill Woodland
	Brazilian pepper tree Schinus terebinthifolius	L		Cedar Grove			TISI, TNC
	Camphor Cinnamomum camphora		Late spring	Lower Park	birds		CAIP, UoF	Spreads easily by seed, can create thousands of seedlings from one tree
	Cherry or purple leaf plum Prunus cerasifera	L	Late Feb-Apr.	Lower, Middle and Upper Park	Birds			Widely naturalized along Sacramento River and other streams from the valley floor into foothill canyons. Native to southeast Europe.
	Chinese hackberry Celtis sinensis			Lower and Middle Park	seed
	Chinese pistache Pistacia chinensis	E	Late March-April	Lower, Middle and Upper Park	Birds			Very common in Lower Park; may want to eradicate female trees to prevent further spreading
	Common myrtle Myrtle communis			4th St. entrance & along Woodland	birds			Doesn’t seem to spread very quickly
	Cotoneaster Cotoneaster franchet (?) pannosa (?)	M	Spring	Cedar Grove				Need to determine exact species
	Field bindweed Convolvuulas arvensis	C	Early April-Oct	Upper Park			TISI, TNC	Grassland
	Golden bamboo Phyllostachys aurea			Lower Park on S. Park Dr.	Wide-creeping rootstocks form solid stands			Small patches creeping in from adjoining residence on S. Park Dr and along path from E 8th St. entrance east of Hwy 99
	Japanese honeysuckle Lonicera japonica		Early May-June	Lower Park			TISI, TNC
	Mediterranean, hoary mustard Hirschfeldia incana	M	Most Months	Lower, Middle and Upper Park	Gravity, Wind			Annual Grassland, Riparian, Foothill Woodland; perennial weed of dry disturbed places
	Moonwort Lunaria annua		Mid Apr.	Lower Park: CSUC Campus	Gravity			Riparian Woodland, landscaped areas, in field east of Hwy 99 on south side of creek
	Northern California black walnut Juglans hindsii		April-May	Lower, Middle and Upper Park	Mammals			Riparian Woodland; no known native stands of Juglans hindsii in Butte County, widely naturalized, under consideration as invasive plant in Bidwell Park because it may significantly reduce oak regeneration
	Pecan Carya illinoinensis		Spring	Lower Park	Squirrels, scrub jays			Escapee from cultivation. Often confused with black walnut
	Prickly lettuce Lactuca serriola		Early April-Nov	Upper Park				Cal-IPC considers it an agricultural weed
	redtip photinia Photinia x fraseri			Lower Park	birds
	Silktree, mimosa Albizia julibrissin		summer and fall	Hooker Oak, near Lower Park walnut orchard			GISD	common Chico tree, spreads easily, seed viable for 50 years, should eradicate the few trees in the park to prevent spread
	Virginia creeper Parthenocissus quinquefolia			Lower Park, north side along creekside trail	birds
	White mulberry. Morus alba		Mid Mar-Apr.	Middle and Upper Park	Birds			Along streams and roads. The plant is dioecious, female trees producing blackberry-like fruits that ripen reddish to black. Native to China.  May want to eliminate female trees to prevent spread.
	Plants ranked #4 on park priority list: Invasive, but too widespread to manage
	Beardgrass, rabbit’s foot grass Polypogon monspeliensis	L	Early Feb	Upper Park
	Bermuda grass Cynodon dactylon	M C	Mid May	Lower, Middle and Upper Park	vegetatively, seed		TISI, TNC
	Big heronbill Erodium botrys		Early March-June	Upper Park by Alligator Hole				Cal-IPC considers impacts to be negligible.
	Bird’s-foot-trefoil Lotus corniculatus		Early April-Sept	Upper Park				Cal-IPC considers it to be primarily an agricultural weed.
	Birdsrape mustard Brassica rapa	L	Early Dec-June	Upper Park by Bear Hole
	Bulbous bluegrass Poa Bulbosa		Early March	Upper Park by Brown’s Hole
	Bur clover Medicago polymorpha	L	Late Feb-June	Lower, Middle and Upper Park				Prefers some shade and is most abundant under brush and trees.
	Chicory Cichorium intybus		Late May-Nov	Lower and Upper Park
	Creeping bentgrass Agrostis stolonifera	L	Early June	Middle Park by Lindo Channel
	Curly dock Rumex crispus	L		Lower, Middle & Upper Park	wind, water
	Curlyleaf pondweed Potamogeton crispus	M	Late May	Horseshoe Lake			GISD
	Cut-leaf blackberry Rubus laciniatus		Early May-Sept	Middle Park by Lindo Channel
	Cutleaf geranium Geranium dissectum		Early March-June	Upper Park
	Dallisgrass Paspalum dilatatum		Early May	Upper Park
	Dovefoot geranium Geranium molle		Early March-April	Upper Park by Salmon Hole				Cal-IPC comment" wildland impacts negligible"
	Everlasting pea Lathyrus latifolius	UC	Mid May-Oct	Upper Park-golf course, Annie’s Glen
	False brome Brachypodium distachyon		Late April	Upper Park by Bear Hole
	Foxtail or rattail fescue Vulpia bromoides		Early March	Upper Park by Bear Hole				Cal-IPC comment:  "less common than v. myuros"
	Fragrant water lily Nymphaea odorata		Mid May-August	Horseshoe Lake
	Hairy or winter vetch Vicia Villosa		Early March-June	Upper Park by Rod and Gun Club				Cal-IPC–"widespread but minor impacts in wildlands"
	Hedgehog dogtail grass Cynosurus echinatus	M	Early May	Upper Park
	Hedgeparsley Torilis arvensis	M	Late April-July	Upper Park North Rim
	Honey locust Gleditsia triacanthos			Lower Park-Cedar Grove, Five Mile				Cal-IPC–"very limited distribution"
	Hyssop loosestrife Lythrum hyssopifolium	L	Early May-Sept	Upper Park
	Indian or yellow sweet clover Melilotus indica	E	Mid April-June	Upper Park by Bear Hole				Cal-IPC-"present in human-disturbed habitats only"
	Italian ryegrass Lolium multiflorum	M	Mid Dec.	Lower, Middle and Upper Park	Wind, Mammals, Water			Annual Grassland, Riparian; dominates clay soils, one of most common grasses in park
	Kentucky bluegrass Poa pratensis ssp. Pratensis	L	Mid April	Upper Park by Salmon Hole			TISI, TNC
	Maritime beard grass Polypogon maritimus		Early April	Upper Park-Horseshoe Lake
	Mediterranean barley Hordeum marinum	M	Late March	Upper Park by Rod and Gun Club			TISI, TNC
	Obtuse filaree Erodium brachycarpum	E	Late Dec-July	Upper Park by Horseshoe Lake				Cal-IPC-"impacts are negligible, transient"
	Orchard grass Dactylis glomerata	L	Mid April	Upper Park by end of Yahi Trail
	Oysterplant, salsify Tragopogon porrifolius		Early April-June	Lower Park by Hwy 99
	Queen Anne’s lace Daucus carota	E	Late April-Oct	Lower Park			TISI, TNC	According to Cal-IPC-"widespread especialy on roadsides"
	Red gum Eucalyptus camaldulensis	L	Early Feb.	Lower, Middle and Upper Park	Wind, Mammals
	Red-stemmed filaree Erodium cicutarium	L	most months	Upper Park Lot P
	Ripgut brome Bromus diandrus	M	Late Feb.	Lower, Middle and Upper Park	Mammals, Wind			Annual Grassland; common grass in Bidwell Park
	Rose clover Trifolium hirtum	M	Late March-June, also early fall	Upper Park
	Russian thistle, tumbleweed Salsola tragus	L C *	Mid June-Nov	Middle Park-Lindo Channel			GISD
	Silver hair grass Aira caryophyllea	E	Mid January	Upper Park North Rim				Cal-IPC-"widespread in grasslands, impacts negligible"
	Slender wild oat Avena barbata	M	Mid Jan.	Lower, Middle and Upper Park	Mammal, Wind			Annual Grassland, openings in Woodland; common grass
	Smooth catsear Hypochaeris glabra	L	Late Feb-July	Upper Park Lot R
	Soft brome Bromus hordeaceus	L	Late January	Upper Park
	Spiny sowthistle Sonchus asper	E	Most months	Upper Park Bear Hole				Cal-IPC-"primarily agricultural weed"
	Subterranean clover Trifolium subterraneum		Early March-June	Upper Park E. end of Yahi Trail
	Tangier pea Lathyrus tingitanus	UC	Early Feb-July	Upper Park by Bear Hole
	Velvet Grass Holcus lanatus	M	Mid April	Upper Park			TISI, TNC
	White horehound Marrubium vulgare	L	Mid April-June, Sept	Upper Park
	White sweet-clover Melilotus alba		Early March-Dec	Upper Park by Rod and Gun Club			TISI, TNC
	White-stemmed filaree Erodium moschatum	E	Late Feb-May	Upper Park				Cal-IPC "primarily an agricultural weed"
	Wild mustard Sinapis arvensis	L	Mid Oct-May	Upper Park by Day Camp
	Wild oat Avena fatua	M	Late Dec.	Lower, Middle and Upper Park	Mammals, Wind			Annual Grassland, openings in Woodland; common grass
	Yellow nutsedge Cyperus esculentus	B	Mid July	Middle Park-Diversion Dam
	Yellow Salsify Tragopogon dubius	E	Mid March-Oct	Upper Park				Cal-IPC "Generally a minor component of disturbed area"
	Plants ranked #5 on park priority list: Non-native, but do not appear to be invasive
	Bee-balm Melissa officinalis		Early June-Sept	Upper Park
	Black Cherry Prunus serotina			Lower Park-Cedar Grove
	English plantain Plantago lanceolata	L	Mid April-Oct	Upper Park
	Green wattle Acacia decurrens (arabica?) (melanoxion?)	E	Early Feb.-Mar.	Lower Park; Cedar Grove	Wind			Riparian-Valley Oak Woodland, road edges-need to confirm species
	Japanese zelkova Zelkova serrata			Lower and Middle Park	spread by seed			On Chico's approved Street Tree List, planted in Cedar Grove Forestry Station
	London plane tree Platanus acerifolia		Late Mar.-Apr.	Lower, Middle and Upper Park	Wind and water			Widely naturalized along most valley and foothill streams. It may have a reproductive advantage over the native sycamore since it appears to be resistant to sycamore anthracnose, which causes die back of twigs and flowers in native sycamore.

Ranking Key

Key to Control Method abbreviations:

Information Sources

• Personal observations by park users:
• Big Chico Creek Watershed Existing Conditions Report (Big Chico Creek Watershed Alliance, 2000):
• Butte County Department of Agriculture Weed Management Area brochure-list titled “Butte County’s Noxious Weeds of Special Concern”:
• CalFlora Database:
• California Department of Food and Agriculture :
• California Invasive Plant Council 1999 rankings:
• California State University, Chico Herbarium database-list of plants collected from Bidwell Park:
• Chico Forestry Station and Nursery 1918 planting maps:
• The Jepson Manual: Higher Plants of California (Hickman, J., Ed., 1993). :
• Invasive Plants of California’s Wildlands (Bossard, C., Randall, J., Hoshovsky, M., Ed, 2000):
• Lost Arboretum: Name Changes and Other Information (Wes Dempsey, distributed at February 22, 2004 walk) :
• Proposed Annie Bidwell Trail Botanical Resource Assessment (California State University Research Foundation, 2000):
• A Resource Inventory of Upper Bidwell Park Expansion Area (California State University Research Foundation, 2000) :
• Selected Plants of Northern California (Vernon Oswald, 2002):
• Survey for Special Status Botanical Species for the City of Chico’s Bidwell Park Trails Project (Kristiaan Stuart, 2002):
• Vascular Plants of Upper Bidwell Park (Vernon Oswald, 1986) :
• Vascular Plants of Butte County (Vernon Oswald, 1994):

Most species nomenclature follows The Jepson Manual: Higher Plants of California
(Hickman, J., Ed., 1993). Common Names and additional information follows
Selected Plants of Northern California and Adjacent Nevada (Oswald, V. 2002)

Bidwell Park Invasive Plant Watch List

To date, these plants have not been identified in Bidwell Park. However, they are considered
very invasive in nearby areas and should be added to the Priority 1 list if or when they are found
in the park.

Common Name Scientific Name	Reason for Inclusion	Photo Link	Control Method
(no common name) Myoporum laetum	On Cal-IPC Invasive Trees of Central CA		Cal-IPC
Artichoke thistle, Cardoon Cynara cardunculus	Found in other local watersheds
Black acacia Acacia melanoxylon	On Cal-IPC Invasive Trees of Central CA		GISD
Carob tree Ceratonia siliqua	seeds spread easily
Creeping water primrose Ludwigia uruguayeniss	On Butte County’s invasive plant list
Diffuse knapweed Centaurea diffusa	On Butte County’s invasive plant list		TISI, TNC
Hoary cress Cardaria draba	On Glenn County’s invasive plant list
Japanese dodder Cuscuta japonica choisy	Cultural uses for plant indicate it may be in Butte County
Parrot Feather Myriophyllum aquaticum	On Butte County’s invasive plant list		GISD
Peruvian pepper tree Schinus molle	On Cal-IPC Invasive Trees of Central CA
Plumeless thistle Carduus acanthiodes	On Glenn County’s invasive plant list
Purple loosestrife Lythrum salicaria	On Butte County’s invasive plant list		TISI, TNC
Purple starthistle Centaurea calcitrapa	On Glenn County’s invasive plant list
Rush skeletonweed Chondrilla juncea	On Butte County’s invasive plant list
Russian olive Elaeagnus angustifolia	On Cal-IPC Invasive Trees of Central CA		TISI, TNC
Scarlet wisteria Sesbania punicea	at Lake Oroville-Red Alert		TISI, TNC
Scotch broom Cytisus scoparius	Found in other local watersheds		TISI, TNC
Slender false-brome Brachypodium sylvaticum	Problem in areas further north
Spotted knapweed Centaurea maculosa	On Butte County’s invasive plant list		TISI, TNC
Stinkweed Dittrichia graveolens	Cal-IPC 2008 Symposium alert
White horsenettle Solanum elaeagnifolium	On Glenn County’s invasive plant list
Wild fennel Foeniculum vulgare	Found nearby, very invasive in other areas		TISI, TNC