Invasive Weeds of the Tahoe National Forest Invasive Weeds of the Tahoe National Forest
Graphic Design Annaliese Miller
Illustrations © Annaliese Miller
Photography courtesy of: Robin Breckenridge, Beth Brenneman, Laura Ann Eliassen, Joe DiTomaso, Susan Donaldson, Louis Landry, Steve Matson, Annaliese Miller, Gary Monroe, Tamara Sasaki, Susi Urie, Charles Webber
Text Susan Donaldson, Susi Urie
United States Forest Service Publication R5-TP-024, 2009 Tahoe National Forest
The USDA Forest Service is an equal opportunity service provider and employer. Adapted with permission from “Invasive Weeds of the Lake Tahoe Basin”, S. Donaldson, University of Nevada Cooperative Extension SP-09-06 copyright 2009.
1 Invasive Weeds of the Tahoe National Forest How to Use the Guidebook
Invasive weeds are aggressive plants that have been This guidebook will help you identify the invasive weeds introduced into an environment outside of their native threatening the Tahoe National Forest. Common “look- range. Sometimes referred to as alien species, these alikes” are also included to help you differentiate between weeds have been separated from the natural enemies that desirable native plants, noted , and undesirable invasives, help control them in their homeland. They grow rapidly, designated . Plants that could potentially become invasive reproduce profusely, and compete with native plants for are marked as . You may choose to avoid planting species water, light and nutrients. Some of these weeds have that may become invasive on your property. Information been designated as noxious by California and Nevada law, on management is also included for each invasive weed, requiring control efforts by property owners. as is the noxious weed status in California. California’s noxious weed rating system designation, which is based Invasive weeds tend to outcompete native plants, especially on distribution of the weed, is also provided. “A” rated where lands have been disturbed. When they displace weeds are normally limited in distribution throughout the native plants and animals, they lower diversity, reduce state; “B” rated weeds are more widespread; and “C” hunting and fishing potential, change the aesthetics of a rated weeds are widespread throughout the state. Nevada habitat, inhibit recreational activities and tourism, crowd weed law uses a similar system. out endangered species, and reduce forage value. Along the Truckee River, weeds that have coarse or shallow root systems, such as perennial pepperweed and dalmatian Relative abundance of each species is provided. toadflax, increase soil erosion and threaten water clarity. Widespread: Found at numerous locations in the area Moderate: Found at several locations; large If you find an invasive weed, please report the infestation populations may occur at a few locations to the appropriate county (see contact numbers on the inside back cover). Infrequent: Only at one or a few locations; no large populations
2 3 Preventing the Spread of Weeds INDEX Common Name (Scientific Name) Code Page THISTLES Prevention is the least expensive and most effective way to Bull Thistle (Cirsium vulgare) CIVU 8-9 halt the spread of noxious and invasive weeds. Canada Thistle (Cirsium arvense) CIAR4 10-11 This requires: Musk Thistle (Carduus nutans) CANU4 12-13 • Educating workers and the public about the Anderson’s Thistle (Cirsium andersonii) CIAN 14-15 importance of managing weeds on an ongoing basis; Elk Thistle (Cirsium scariosum) CISC2 16-17 • Properly identifying weed species; Snowy Thistle (Cirsium occidentale var. candidissimum) CIOCC 18-19 • Avoiding or treating existing weed populations; and • Preventing weed seeds or other plant parts from KNAPWEEDS AND LOOK-ALIKES establishing new or bigger populations. Diffuse Knapweed (Centaurea diffusa) CEDI3 20-21 Russian Knapweed (Acroptilon repens) ACRE3 22-23 Steps you can take: Spotted Knapweed (Centaurea maculosa) CEMA4 24-25 1. Use this book to identify invasive weeds in your area. Yellow Starthistle (Centaurea solstitialis) CESO3 26-27 2. Inspect your work or play area. Identify any invasive Aster (Aster spp.) 28-29 weeds, map the location of the weeds. Bachelor’s Buttons (Centaurea cyanus) CECY2 30-31 3. Clean vehicles, shovels and other soil-disturbing equipment prior to entering a site to avoid MUSTARDS AND LOOK-ALIKES introducing weeds. Hoary Cress (Cardaria draba) CADR 32-33 4. Don’t introduce weed-contaminated soil, fill, or other Perennial Pepperweed (Lepidium latifolium) LELA2 34-35 materials to new sites. Use certified weed-free products. Poison Hemlock (Conium maculatum) COMA2 36-37 5. Check shoes, clothing, bicycles and vehicles regularly White Sweetclover (Melilotus albus) MEAL12 38-39 for weed seeds or other plant parts. Carefully remove Yarrow (Achillea millefolium) ACME 40-41 and dispose of weedy materials. TOADFLAXES AND LOOK-ALIKES 6. Pressure-wash vehicles and equipment after driving Dalmatian Toadflax (Linaria dalmatica) LIDA 42-43 in weedy areas. Periodically monitor and treat areas Yellow Toadflax (Linaria vulgaris) LIVU2 44-45 to prevent weedy plants from establishing. Snapdragon (Antirrhinum majus) ANMA3 46-47 7. Establish a decontamination area such as a tarp for cleaning clothing and equipment. AQUATIC 8. Don’t walk, ride or drive through infestations. When Eurasian watermilfoil (Myriophyllum spicatum) MYSP2 48-49 operating vehicles, stay on established roads or trails. Common elodea (Elodea canadensis) ELCA7 50-51 9. If dogs accompany you, check their paws and coats OTHERS for weed seeds and other plant parts and remove them. Klamathweed (Hypericum perforatum) HYPE 52-53 10. Don’t plant invasive weeds in your garden or landscape. Scouler’s St. Johnswort 11. Get advice for treatment on private property from your (Hypericum formosum var. scouleri) HYFOS2 54-55 local county agriculture department. See contact Rush skeletonweed (Chondrilla juncea) CHJU 56-57 information on back page. Scotch Broom (Cytisus scoparius) CYSC4 58-59 Teasel (Dipsacus fullonum) DIFU2 60-61 4 5 QUICK REFERENCE ID QUICK REFERENCE ID
THISTLES Flower Head Leaves KNAPWEEDS Bracts Lower Leaves
Diffuse Bull Thistle Knapweed rough, deeply vase veins spiny combs lobed
Russian Canada Thistle lobed, Knapweed drop spiny papery lobed
Spotted Musk Thistle midrib, Knapweed deeply disk hairless spots lobed
Yellow Anderson’s Starthistle spines Thistle winged small stem (look-alike) cylinder flat hairs
Aster spp. narrow, (look-alike) no spines, entire Elk Thistle long yellow disk (look-alike) no stems hairs
Bachelor Buttons narrow, no spots entire (look-alike) Snowy Thistle wooly (look-alike) reflexed bracts hairs
6 7 BULL THISTLE Cirsium vulgare CIVU Nonnative Invasive
Tops of leaves rough, sandpaper texture
Underside of leaf cottony, prominently raised main vein
1 - 1.5 in
Plant, Brenneman; Flower, Donaldson Plant, Brenneman; Flower, Flower head vase-shaped
Rosette leaves rough, prominent veins Also Known As Common thistle Origin Nonnative, invasive Height: 1 - 6 ft, Habitat Meadows, roadsides, disturbed sites commonly 2 - 3 ft Life Cycle Biennial n Stems: spiny and winged Flowering Time Mid-July to fall n Leaves: sandpaper texture, Relative Abundance Widespread prominent veins Management Dig, removing top 2 inches of root; n Flowers: in clusters at herbicides are available ends of branches Noxious Weed List Nevada-NO; California C-rated n Flower color: pink to purple 8 9 CANADA THISTLE Cirsium arvense CIAR4 Nonnative Invasive
Bracts small and flat against head, tips weak
0.5 in
Donaldson Flower head drop-shaped
Leaves deeply lobed
Also Known As Field thistle Height: 1.5 - 4 ft, Origin Nonnative, invasive commonly 2 - 3 ft Habitat Roadsides, rangelands, forests, lawns, n Stems: smooth and ridged gardens, moist and disturbed sites with no spines Life Cycle Perennial n Leaves: smooth and Flowering Time Mid-July to fall sessile Relative Abundance Infrequent n Flowers: multiple Management Aggressive; pulling and burning favor small flower heads in root resprouting; use chemical clusters on each stem control for several years n Flower color: Noxious Weed List Nevada C-rated; California B-rated light purple to white
10 11 MUSK THISTLE Carduus nutans CANU4 Nonnative Invasive
Bracts large and spiny; purplish in color
2 - 3.5 in
Flower head disk-shaped
Light-green Rosette leaves hairless, midrib Plant, Miller; Flower, Donaldson Plant, Miller; Flower, light-green midrib, whitish margins
Also Known As Nodding thistle Height: 1 - 6 ft Origin Nonnative, invasive commonly 3 - 4 ft Habitat Pastures, forest, rangelands, n Stems: spiny and winged roadsides, waste areas, ditches n Leaves: hairless, prominent Life Cycle Biennial light-green midrib Flowering Time Mid-July to fall n Flowers: single, very large Relative Abundance Infrequent flower at end of bent, naked stem Management Dig, removing top 2 inches of root; herbicides are available n Flower color: deep pink to purple Noxious Weed List Nevada B-rated; California A-rated 12 13 ANDERSON’S THISTLE Cirsium andersonii CIAN Native Look-alike
0.75 - 1.5 in
Brenneman Flower head cylinder-shaped Leaf margins wavy and spiny
Rosette leaves not prominently veined, small flat hairs
Also Known As Rose thistle Height: 2 - 4 ft Origin Native n Stems: purplish and Habitat Open places, woodlands, forests thornless Life Cycle Biennial n Leaves: divided and wavy Flowering Time July to fall with spiny margin Relative Abundance Widespread n Flowers: single Management Desirable native plant; do not disturb flower at end of stem Noxious Weed List Nevada-NO; California-NO n Flower color: rose red to reddish purple
14 15 ELK THISTLE Cirsium scariosum CISC2 Native Look-alike
Stemless flower Brenneman
Rosette leaves have long golden hairs; long fine spines at leaf margins
Height: up to 3 ft, Also Known As Drummond’s thistle generally less than 1 ft Origin Native n Stems: usually no stems; Habitat Moist places at mid to high elevations forms round flat rosette Life Cycle Biennial n Leaves: lobed, somewhat Flowering Time June to August spiny, pale green foliage Relative Abundance Moderate n Flowers: extend directly Management Desirable native plant; do not disturb from rosette Noxious Weed List Nevada-NO; California-NO n Flower color: white to pale lavender
16 17 Cirsium occidentale SNOWY THISTLE var. candidissimum CIOCC Native
Large reflexed bracts, wooly hairs Plant, Urie; Flower, Monroe Calphotos Plant, Urie; Flower,
3/4 - 2 in
Densely white wooly hairs
Height: 1.5 to 6.5 ft Also Known As None n Stems: densely Origin Native white wooly hairs Habitat Disturbed areas, shrubby areas, n open woodlands Leaves: densely white wooly hairs on both Life Cycle Biennial surfaces Flowering Time July to September n Flowers: single or in Relative Abundance Widespread in Northern California clusters at the end of Management Desirable native plant; do not disturb branches Noxious Weed List Nevada-NO; California NO n Flower color: pink to red
18 19 DIFFUSE KNAPWEED Centaurea diffusa CEDI3 Nonnative Invasive
Bract tips spiny; margins divided like teeth of comb
Upper leaves narrow and entire Donaldson
Stems stiff and widely branching
Lower leaves Also Known As Tumble knapweed deeply lobed Origin Nonnative, invasive
Habitat Roadsides, waste areas, dry Height: 1 - 2.5 ft rangelands, disturbed sites n Stems: rough to touch Life Cycle Annual to short-lived perennial n Flowering Time June to August Leaves: upper, entire; lower, deeply lobed Relative Abundance Infrequent n Growth form: maintains Management Minimize seed production; pull or dig bush shape; after frost, plants several times per year and can break off and tumble monitor for several years; herbicides are available n Flower color: white to pale pink Noxious Weed List Nevada B-rated; California A-rated 20 21 RUSSIAN KNAPWEED Acroptilon repens ACRE Nonnative Invasive
Bract margins papery, NOT spiny
Upper leaves narrow and entire Donaldson
Stems openly branched
Lower leaves lobed
Also Known As Creeping knapweed Height: 1 - 3 ft, Origin Nonnative, invasive generally 2 - 3 ft Habitat Roadsides, riverbanks, ditches, n Stems: erect, cobwebby pastures, waste places n Leaves: upper, entire; Life Cycle Rhizomatous perennial lower and rosette, lobed Flowering Time July to fall n Growth form: thick Relative Abundance Infrequent rounded clumps with Management Cut or mow prior to seed set to reduce drooping branches current year’s growth; chemical control n Root: black below crown is needed n Flower color: pink to purple Noxious Weed List Nevada B-rated; California B-rated 22 23 SPOTTED KNAPWEED Centaurea maculosa CEMA4 Nonnative Invasive
Bract tips dark, finely fringed, spineless
Upper leaves narrow and entire Plant, Breckenridge CDFA; Flower, Donaldson Flower, Plant, Breckenridge CDFA;
Lower leaves deeply lobed Stems openly and smooth branched Note leaf Also Known As Centaurea stoebe placement Origin Nonnative, invasive Habitat Disturbed soil, rangelands, pastures, meadows, roadsides, areas with Height: 1 - 5 ft; summer rainfall generally closer to 3 ft Life Cycle Perennial; sometimes biennial n Stems: erect and rough Flowering Time July to early September n Leaves: upper, linear; Relative Abundance Moderate lower, divided Management Minimize seed production by cutting n Growth form: tall with or mowing; dig, removing top 2 - 6 in of open branching root; herbicides are available n Flower color: pink to purple Noxious Weed List Nevada A-rated; California A-rated 24 25 YELLOW STARTHISTLE Centaurea solstitialis CESO3 Nonnative Invasive
Long spines at tips of bracts (up to 1 in long)
Upper leaves
Donaldson entire
Lower leaves deeply lobed
Also Known As None Height: 0.5 - 5 ft, Origin Nonnative, invasive commonly 2 ft Habitat Roadsides, waste areas, grasslands n Stems: winged Life Cycle Annual n Leaves: gray and hairy; Flowering Time Late June to September upper, entire; Relative Abundance Infrequent lower, deeply lobed Management Pull, dig or mow at first sign of yellow n Growth form: stiffly flowers; herbicides are available branching Noxious Weed List Nevada A-rated; California C-rated n Flower color: yellow
26 27 ASTER Aster spp. ASTER Native Look-alike
Bracts do not have spines
Donaldson Leaves narrow and entire
Also Known As Various Height: variable, Origin Native often 1 - 2 ft n Habitat Meadows, gardens Stems: smooth to hairy n Life Cycle Annual or perennial Leaves: upper and lower leaves narrow and entire Flowering Time Late July to fall n Growth form: ranges from Relative Abundance Widespread short to tall Management Desirable native plant; do not disturb n Flower color: variable, Noxious Weed List Nevada-NO; California-NO often pink to purple with yellow center
28 29 BACHELOR’S BUTTONS Centaurea cyanus CECY2 Nonnative Look-alike
Bract tips pale, finely fringed, spineless Donaldson
Leaves narrow and entire; generally not toothed except lower leaves
Also Known As Cornflower Origin Nonnative, can be invasive, has escaped from cultivation Height: up to 3 ft Habitat Disturbed grasslands, open woods, n Stems: erect and branching ornamental plantings n Leaves: grayish and hairy; Life Cycle Annual upper and lower leaves narrow and entire Flowering Time July to September Relative Abundance Widespread n Growth form: tall, bushy Management Mechanical controls (pull, dig, hoe); n Flower color: multicolored herbicides are available (white, blue, purple, pink, red) Noxious Weed List Nevada-NO; California-NO 30 31
HOARY CRESS Cardaria draba CADR Nonnative Invasive
Single stem
Tiny 4-petaled flowers in dense clusters near ends of branches Donaldson 2 lobes clasp stem on upper leaves
Leaves lance-shaped
Also Known As Whitetop, short whitetop, Cardaria pubescens Origin Nonnative, invasive Habitat Meadows, fields, roadsides, ditches, streambanks, rangelands Height: up to 2 ft, Life Cycle Rhizomatous perennial commonly 1 ft Flowering Time May to June n Stems: single stem gives Relative Abundance Infrequent rise to one flower cluster Management Mow two to three times per year at n Leaves: blue-green foliage; bud stage to slow spread; do not pull, upper leaves clasp stem; as plants will grow from root fragments; lower leaves petiolate chemical control is needed n Flower color: white Noxious Weed List Nevada C-rated; California B-rated 32 33 PERENNIAL PEPPERWEED Lepidium latifolium LELA2 Nonnative Invasive
multiple branches
Tiny 4-petaled flowers in dense clusters near ends of branches Donaldson
Stems branch from juncture of leaf with main stem Leaves lance-shaped; leaf margins smooth or toothed
Also Known As Tall whitetop Origin Nonnative, invasive Height: 1 - 6 ft, Habitat Riparian areas, floodplains, meadows, commonly 3+ ft seasonally wet areas, roadsides Stems: multiple branches Life Cycle Rhizomatous perennial grow from each stem Flowering Time Late June to August Leaves: upper leaves, Relative Abundance Moderate sessile; lower leaves, petiolate; basal leaves, Management Do not pull, dig, or cut the roots, much larger than upper as this may stimulate new growth; leaves chemical control is needed n Noxious Weed List Nevada C-rated; California B-rated Flower color: white 34 35 POISON HEMLOCK Conium maculatum L. COMA2 Nonnative Invasive
Secondary Umbel
Secondary Umbel Umbel Leaves fern-like Urie
Stems light green with purple spots
Also Known As Poison parsley Extremely poisonous if ingested Origin Nonnative, invasive Height: 3 - 8 ft, Habitat Wet areas in meadows, seeps, springs commonly 3+ ft and floodplains Stems: branched, light Life Cycle Biennial green with purple spots Flowering Time July to Fall Leaves: compound, lacy resembling parsley, Management Manual hand-pulling or multiple mowing seedlings may appear or chemical control fern-like Noxious Weed List Nevada-YES; California-NO n Flower color: white
36 37 WHITE SWEETCLOVER Melilotus albus MEAL12 Nonnative Look-alike
Many small fragrant flowers Pea-shaped borne on flowers irregular spikes at the ends of elongated stems Brenneman
Leaves consist of 3 leaflets, margins finely toothed
Also Known As None Origin Nonnative, used in soil stabilization mixes Habitat Roadsides, waste areas Life Cycle Annual to biennial Height: 2 - 6 ft, commonly about 3 - 5 ft Flowering Time June to August n Stems: well-branched and Relative Abundance Widespread coarse Management Hand pull wearing gloves; dig or mow n Leaves: 3 leaflets prior to seed set; herbicides available n Noxious Weed List Nevada-NO; California-NO Flower color: white 38 39 YARROW Achillea millefolium ACMI2 Native Look-alike
Flower heads flattened, dome-shaped corymbs
Leaves hairy and very finely pinnately
Plant, Brenneman; Flower, Donaldson Plant, Brenneman; Flower, divided, appearing feather-like
Also Known As Common yarrow, milfoil Origin Native and introduced, can be invasive Habitat Gardens, meadows, grasslands, forests Life Cycle Perennial Height: 2 - 3 ft Flowering Time June to September n Stems: hairy-wooly Relative Abundance Widespread n Leaves: feather-like; evenly Management Dig, removing as much root as distributed along stem; possible; forms dense mat if mowed; lower leaves larger chemical control is available n Flower color: white or pink Noxious Weed List Nevada-NO; California-NO 40 41 DALMATIAN TOADFLAX Linaria dalmatica LIDA Nonnative Invasive
Leaves ovate, Spurs long, tips pointed somewhat curved or straight Donaldson
Flowers borne in axils of upper leaves and bracts
Leaves clasp stem Also Known As Wild snapdragon, Linaria genistifolia ssp. dalmatica Origin Nonnative, invasive Height: up to 3 ft Habitat Roadsides, pastures, rangelands, Stems: erect and branched cultivated fields Leaves: ovate, alternate Life Cycle Perennial and entire; succulent and waxy Flowering Time July to fall Relative Abundance Moderate Growth form: more scattered than yellow Management Pull or dig for several years, removing toadflax as much root as possible; do not mow; chemical control is available Flower color: yellow, with orange, bearded throat Noxious Weed List Nevada A-rated; California A-rated 42 43 YELLOW TOADFLAX Linaria vulgaris LIVU2 Nonnative Invasive
Spur Plant, Brenneman; Flower, Charles Webber © CA Academy Charles Webber Plant, Brenneman; Flower, of Sciences
Leaves linear, pointed at both ends Leaves alternate, crowded close together
Also Known As Butter and eggs Origin Nonnative, invasive Height: 1 - 2 ft; Habitat Rangelands, roadsides, waste places, shorter than dalmatian cultivated fields toadflax Life Cycle Perennial Leaves: linear, smooth to Flowering Time July to fall sparsely hairy; succulent and waxy Relative Abundance Moderate Growth form: tends to Management Pull or dig for several years, removing grow in crowded patches as much root as possible; do not mow; chemical control is available Flower color: yellow, with orange, bearded throat Noxious Weed List Nevada A-rated; California-NO 44 45 SNAPDRAGON Antirrhinum majus ANMA3 Nonnative Look-alike
Flowers in terminal racemes
No spur Plant, Brenneman; Flower, Donaldson Plant, Brenneman; Flower,
Upper leaves long and narrow Lower leaves lanceolate
Also Known As None Origin Nonnative Habitat Ornamental gardens Height: 0.5 - 3 ft Life Cycle Annual to perennial n Leaves: upper, long and Flowering Time June to fall narrow; lower, lanceolate; Relative Abundance Widespread soft, not waxy n Management None; recommended garden flower Flowers: fuzzy-hairy Noxious Weed List Nevada-NO; California-NO n Flower color: yellow, but other colors are available
46 47 Myriophyllum EURASIAN WATERMILFOIL spicatum MYSP Nonnative Invasive
14+ leaflet pairs per leaf. Native 5-12 leaflet pairs.
Leaves collapse Habit, Sasaki; Close-up, DiTomaso Calphotos Habit, Sasaki; Close-up, DiTomaso when out of water. Native stiffer, does not collapse.
Leaves arranged in whorls of 4 around stem at each node
n Growth form: submersed aquatic; forms mats; Also Known As Spike watermilfoil spreads by plant fragments n Origin Nonnative, invasive Stems: branch near water’s surface; growing Habitat Ponds, ditches, streams, lakes stems and tips are red Life Cycle Perennial n Leaves: feather-like; dark Flowering Time June through September green to brown Management Hand removal, taking care to avoid n Flowers: tiny and stand releasing fragments above the water surface Noxious Weed List Nevada-YES; California-NO n Flower color: pinkish; spike inflorescence
48 49 COMMON ELODEA Elodea canadensis ELCA7 Native Look-alike
Leaves arranged Habit, Miller; Close-up, Landry Calphotos in whorls of 3
Leaves do not collapse when out of water.
Also Known As American waterweed, Growth form: submersed Canadian waterweed aquatic; spreads by plant fragments and turions Origin Native n Stems: branch at nodes Habitat Ponds, ditches, streams, lakes, reservoirs n Leaves: dark green, Life Cycle Perennial most often in whorls of 3; Flowering Time Summer lanceolate to oblong Management Usually not a problem, remove by hand n Flower color: white; when it becomes dominant or problematic flowers bloom at the water surface; have 3 small petals Noxious Weed List Nevada-NO; California-NO 50 51 KLAMATHWEED Hypericum perforatum HYPE Nonnative Invasive
Older flower petals twist
5 separate petals
Occasional tiny black dots at Flat-topped edges of petals cymes
More flowers per stem 1 in than native Brenneman Transparent dots on leaves
Height: 1 - 3+ ft Also Known As St. John’s Wort n Stems: erect with numerous Origin Nonnative, invasive rust-colored branches Habitat Pastures, meadows, roadsides, n Leaves: elliptic to oblong, waste areas entire, opposite, sessile; Life Cycle Perennial not over 1 in long Flowering Time June to late September n Growth form: bushy Relative Abundance Moderate n Branches: somewhat Management Pull or dig repeatedly; use biocontrol 2-ridged and woody at insects; chemicals are available the base Noxious Weed List Nevada A-rated; California C-rated n Flower color: yellow 52 53 Hypericum formosum SCOULER’S ST. JOHNSWORT var. scouleri HYFOS2 Native Look-Alike
5 separate petals
Tiny black dots at edges of petals
1 in
Fewer flowers per stem than Plant, Eliassen Calphotos ; Flower, Matson Calphotos Plant, Eliassen Calphotos ; Flower, Leaf margins invasive black-dotted, lower surface inconspicuously dotted
Also Known As None Origin Native Height: 0.5 - 2.5 ft Habitat Streambanks, meadows n Stems: slender; extend from base Life Cycle Tap-rooted perennial n Leaves: ovate to oblong, Flowering Time Summer flat, more or less clasping Relative Abundance Moderate n Growth form: upright Management Desirable native plant; do not disturb and stemmy Noxious Weed List Nevada-NO; California-NO n Flower color: yellow
54 55 RUSH SKELETONWEED Chondrilla juncea CHJU Nonnative Invasive
Lower 4 - 6 inches of stem has downwardly bent coarse hairs DiTomaso
Rosette leaves sharply toothed
Stems smooth above Also Known As Skeleton weed Origin Nonnative, invasive Height: 1 - 4 ft Habitat Roadsides, rangelands, pastures, disturbed soils n Stems: rigid and wiry; highly branched; cut Life Cycle Perennial with extensive, deep root system surfaces exude milky sap Flowering Time Mid-July through frost n Leaves: upper, narrow and entire, inconspicuous; Relative Abundance Infrequent stems often lack leaves Management Difficult to control without herbicides n Growth form: bushy due to extensive deep root system n Flower color: yellow Noxious Weed List Nevada A-rated; California A-rated 56 57 SCOTCH BROOM Cytisus scoparius CYSC4 Nonnative Invasive
Numerous showy pea-like flowers
Flattened, hairy, brown to black seed pods
Upper leaves simple and entire Donaldson
Branches: many Lower leaves leafless or have 3 leaflets, hairy few leaves
Height: woody shrub Also Known As None. Other brooms, deemed up to 10 ft “sterile cultivars,” are available. n Stems: hairy when young, Origin Nonnative, invasive then generally smooth; Habitat Pastures, forests, waste areas most sharply 5-angled or ridged Life Cycle Perennial n Branches: dark green; Flowering Time June to August more-or-less erect
Relative Abundance Moderate n Leaves: upper, simple Management Cut stems at ground level in late and entire; lower, summer; pull seedlings; dig plants; 3 leaflets, hairy use weed wrench to remove root; herbicides are available n Flower color: pale to deep yellow Noxious Weed List Nevada-NO; California C-rated 58 59 TEASEL Dipsacus fullonum DIFU2 Nonnative Invasive
Flowers in dense egg-like heads with large, spine-like bracts
Ridges lined with stiff prickles DiTomaso
Leaves paired, fused at base around stem Stiff prickles on lower midrib
Height: to 7 feet tall, Also Known As Common teasel, wild teasel commonly 3+ feet Origin Nonnative, invasive n Stems: branched, Habitat Irrigation ditches, canals, wetlands, rough and spiny riparian areas, disturbed sites n Leaves: conspicuously Life Cycle Tap-rooted biennial veined; stem leaves lanceolate and up Flowering Time July to fall to 10 inches long Relative Abundance Infrequent n Growth form: erect Management Dig or hand-pull, removing as much root as possible; herbicides are available n Flower color: lavender to purple, rarely white Noxious Weed List Nevada-NO; California-NO 60 61 GLOSSARY GLOSSARY
Alternate: Borne singly at each node, such as leaves. Palmate: Having three or more veins or lobes radiating Axil: The point formed between the stem and any part, from a central point, similar to the fingers on a hand. such as a leaf, attached to it. Panicle: A branched inflorescence in which the flowers Bract: A modified leaf at the base of a flower. bloom from the bottom up. Corymb: A flat-topped or round-topped arrangement of Petiole: The stalk of a leaf. flowers where the lower flower stalks are longer than the Pinnate: A compound leaf with leaflets arranged on upper stalks. opposite sides of the axis. Cyme: A flat-topped or round-topped arrangement of Raceme: A simple, elongated arrangement of flowers. flowers in which the terminal flower blooms first. Ray flower: The long, narrow flower that radiates Crenulate: Having very small, rounded teeth on the leaf outward from the disk flower in the Asteraceae family. margin. Each ray flower resembles a single petal. Disk flower: The tiny, tubular flower of the Asteraceae Rhizomatous: Having rhizomes, or horizontal that forms the center disk of the flowerhead. underground stems that produce shoots above and Divided: Deeply lobed leaf in which lobes are indented to roots below. the base or the midrib. Rosette: A dense, basal cluster of leaves arranged in a Elliptic: Shaped like an ellipse or a narrow oval, broadest circular fashion around one point, usually at ground level. in the middle. Serrate: With sharp teeth directed forward; generally Entire: The margins are smooth, without teeth or lobes. refers to leaf edges. Inflorescence: A flower cluster. Sessile: Without a stalk of any kind; for example, a leaf directly attached to a stem. Linear: Narrow and flat with sides or edges parallel, as in a leaf. Spatulate: Shaped like a spatula, with a rounded blade that tapers to the base. Lobed: Bearing lobes cut less than halfway to base or midvein. Spike: An unbranched, long flower stalk in which the flowers attach directly to the stem and mature from the Margin: The outer edge of the leaf, which may be bottom upwards. smooth, serrated, lobed, etc. Toothed: Having sharp points or lobes along a margin, as Midrib: The middle vein of a leaf. on a leaf. Oblong: Leaf shape in which the leaf is two to four times Turion: Detached winter bud by means of which many longer than it is wide, with nearly parallel sides. water plants survive winter. Opposite: Leaves or other structures borne across from Umbel: A flat-topped flower arrangement. each other at the same node. Winged stem: A stem with one or more thin, flat Ovate Leaf: Egg-shaped leaf that is attached at the margins protruding along the length of the stem. broad end. 62 63 WEED MAPPING CONTACT INFORMATION
For weed information and mapping on the Tahoe The Nevada-Placer Weed Management Group and the National Forest, contact: Tahoe National Forest have been mapping weeds since Tahoe National Forest East Zone Botanist 2001. Regular mapping and inventory helps us determine (530) 587-3558 which species are present in the area, what management Email contact information methods are appropriate, and whether management has [email protected] been a success. We can also track patterns of spread and plan preventive practices. For weed control information on private land contact: Nevada County Agriculture Department We welcome your mapping information. (530) 273-2648 Please include: Placer County Agriculture Department the date surveyed • (530) 889-7372 • the weed name and code (preferably the Sierra County Agriculture Department scientific name) (530) 283-6365 • the location of the observation using UTMs Natural Resources Conservation Service if available. If using a global positioning system (530) 283-7510 (GPS) unit, set your meter to datum NAD83. Funded by: • a thorough description of the location
• the size of the infestation in square feet or acres • the density of the infestation (number of plants or estimated percent cover) • any control methods you employed
Please do not take any management actions or remove Adapted with permission from “Invasive Weeds of the plants until they have been positively identified. Consult Lake Tahoe Basin”, S. Donaldson, University of Nevada your county or Tahoe National Forest weed contact for Cooperative Extension, SP-09-06, copyright 2009. assistance.
Forward the data to the appropriate contact. See listings on next page.
Illustrations © Annaliese Miller - Contact her at: [email protected]
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