Invasive Weeds of the Lake Tahoe Basin

Transcription

1 Invasive Weeds of the Lake Tahoe Basin EB-04-05

2 Invasive Weeds of the Lake Tahoe Basin Art & Layout Annaliese Miller Photography Beth Brenneman, Susan Donaldson Tony Morosco, Charles Webber Text Susan Donaldson Copyright 2004 UNCE University of Nevada Cooperative Extension The University of Nevada, Reno is an Equal Employment Opportunity/ Affirmative Action employer and does not discriminate on the basis of race, color, religion, sex, age, creed, national origin, veteran status, physical or mental disability, and sexual orientation in any program or activity it operates. The University of Nevada employs only United States citizens and aliens lawfully authorized to work in the United States. 1

3 Invasive Weeds of the Lake Tahoe Basin Invasive weeds are aggressive plants that have been introduced into an environment outside of their native range. Sometimes referred to as alien species, these weeds have been separated from the natural enemies that help control them in their homeland. They grow rapidly, reproduce profusely, and compete with native plants for water, light, and nutrients. Some of these weeds have been designated as noxious by California and Nevada law, requiring control efforts by property owners. INDEX Common Name (Scientific Name) Code Page THISTLES Bull Thistle (Cirsium vulgare) CIVU 6-7 Canada Thistle (Cirsium arvense) CIAR4 8-9 Musk Thistle (Carduus nutans) CANU Scotch Thistle (Onopordum acanthium) ONAC Anderson s Thistle (Cirsium andersonii) CIAN Elk Thistle (Cirsium scariosum) CISC Invasive weeds tend to outcompete native plants, especially where lands have been disturbed. When they displace native plants and animals, they lower diversity, reduce hunting and fishing potential, change the aesthetics of a habitat, inhibit recreational activities and tourism, crowd out endangered species, and reduce forage value. At Lake Tahoe, weeds that have coarse or shallow root systems, such as perennial pepperweed and dalmatian toadflax, increase soil erosion and threaten lake clarity. This guidebook will help you identify the invasive weeds threatening the Lake Tahoe Basin. Common look-alikes are also included to help you differentiate between desirable native plants, noted J, and undesirable invasives, designated L. Plants that could potentially become invasive are marked as K. You may choose to avoid planting these species on your property. Information on management is also included for each invasive weed, as is the noxious weed status in Nevada and California. California s noxious weed rating system designation, which is based on distribution of the weed, is also provided. A rated weeds are normally limited in distribution throughout the state; B rated weeds are more widespread; and C rated weeds are widespread throughout the state. If you find an invasive weed, please report the infestation to the appropriate county (see contact numbers on the inside back cover). KNAPWEEDS AND LOOK-ALIKES Diffuse Knapweed (Centaurea diffusa) CEDI Russian Knapweed (Acroptilon repens) ACRE Spotted Knapweed (Centaurea maculosa) CEMA Yellow Starthistle (Centaurea solstitialis) CESO Aster (Aster spp.) Bachelor Buttons (Centaurea cyanus) CECY MUSTARDS AND LOOK-ALIKES Hoary Cress (Cardaria draba) CADR Perennial Pepperweed (Lepidium latifolium) LELA White Sweetclover (Melilotus alba) MEAL Yarrow (Achillea millefolium) ACME TOADFLAXES AND LOOK-ALIKES Dalmatian Toadflax (Linaria dalmatica) LIDA Yellow Toadflax (Linaria vulgaris) LIVU Snapdragon (Antirrhinum majus) ANMA DAISIES Oxeye Daisy (Leucanthemum vulgare) LEVU Shasta Daisy (Leucanthemum X superbum) LESU OTHERS Klamathweed (Hypericum perforatum) HYPE Scotch Broom (Cytisus scoparius) CYSC

4 QUICK REFERENCE ID QUICK REFERENCE ID THISTLES Flower Head Leaves KNAPWEEDS Bracts Lower Leaves Bull Thistle vase rough, veins Diffuse Knapweed combs deeply lobed Canada Thistle drop lobed, spiny Russian Knapweed papery lobed Musk Thistle disk midrib, hairless Spotted Knapweed spots deeply lobed Scotch Thistle oval cobweb hairy Yellow Starthistle spines winged stem Anderson s Thistle cylinder small flat hairs Aster Sp. (look-alike) yellow disk narrow, entire Elk Thistle no stems long hairs Bachelor Buttons (look-alike) no spots narrow, entire 4 5

5 BULL THISTLE Cirsium vulgare CIVU Tops of leaves rough, sandpaper texture Plant, Brenneman; Flower, Donaldson in Flower head vase-shaped Underside of leaf cottony, prominently raised main vein Rosette leaves rough, prominent veins Common thistle Pastures, roadsides, disturbed sites Biennial Mid-July to fall Dig, removing top 2 inches of root; herbicides are available Nevada-NO; California-YES, not yet rated 6 7 Height: 1-6 ft, commonly 2-3 ft Stems: spiny and winged Leaves: sandpaper texture, prominent veins Flowers: in clusters at ends of branches Flower color: pink to purple

6 CANADA THISTLE Cirsium arvense CIAR4 Bracts small and flat against head, tips weak Donaldson 0.5 in Flower head drop-shaped Leaves deeply lobed Field thistle Roadsides, rangelands, forests, lawns, gardens, moist and disturbed sites Perennial Mid-July to fall Aggressive; pulling and burning favor root resprouting; use chemical control for several years Nevada-YES; California-YES, B-rated Height: ft, commonly 2-3 ft Stems: smooth and ridged with no spines Leaves: smooth and sessile Flowers: multiple small flower heads in clusters on each stem Flower color: light purple to white 8 9

7 MUSK THISTLE Carduus nutans CANU4 Bracts large and spiny; purplish in color in Donaldson Flower head disk-shaped Light-green midrib Nodding thistle Pastures, forest, rangelands, roadsides, waste areas, ditches Biennial Mid-July to fall Dig, removing top 2 inches of root; herbicides are available Nevada-YES; California-YES, A-rated Height: 1-6 ft commonly 3-4 ft Stems: spiny and winged Leaves: smooth, prominent light-green midrib Flowers: single, very large flower at end of bent, naked stem Flower color: deep pink to purple

8 SCOTCH THISTLE Onopordum acanthium ONAC Many spiny, needle-like bracts 1-2 in Flower head flattened globe Leaves hairy, giving a grayish appearance Donaldson Stems spiny and winged Winged thistle Waste areas, roadsides, disturbed soils Biennial; rarely annual Mid-July to fall Dig, removing top 2 inches of root; herbicides are available Nevada-YES; California-YES, A-rated Height: up to 10 ft, commonly 5+ ft (the tallest of the thistles) Stems: spiny, prominently winged Leaves: hairy and sessile Flowers: in groups of 2 or 3 on branched tips Flower color: purple 12 13

9 ANDERSON S THISTLE Cirsium andersonii CIAN Native Look-alike Brenneman in Flower head cylinder-shaped Leaf margins wavy and spiny Rosette leaves not prominently veined, small flat hairs Rose thistle Native Open places, woodlands, forests Biennial Mid-July to fall Desirable native plant; do not disturb Nevada-NO; California-NO Height: 2-4 ft Stems: purplish and thornless Leaves: divided and wavy with spiny margin Flowers: single flower at end of stem Flower color: rose red to reddish purple 14 15

10 ELK THISTLE Cirsium scariosum CISC2 Native Look-alike Stemless flower Brenneman Rosette leaves have long golden hairs; long fine spines at leaf margins Drummond s thistle Native Moist places at mid- to high elevations Biennial June to August Desirable native plant; do not disturb Nevada-NO; California-NO Height: up to 3 ft, generally less than 1 ft Stems: usually no stems; forms round flat rosette Leaves: lobed, somewhat spiny, pale green foliage Flowers: extend directly from rosette Flower color: white to pale lavender 16 17

11 DIFFUSE KNAPWEED Centaurea diffusa CEDI3 Bract tips spiny; margins divided like teeth of comb Upper leaves narrow and entire Donaldson Stems stiff and widely branching Tumble knapweed Roadsides, waste areas, dry rangelands, disturbed sites Annual to short-lived perennial June to August Minimize seed production; pull or dig plants several times per year and monitor for several years; herbicides are available Nevada-YES; California-YES, A-rated Lower leaves deeply lobed Height: ft Stems: rough to touch Leaves: upper, entire; lower, deeply lobed Growth form: maintains bush shape; after frost, can break off and tumble Flower color: white to pale pink

12 RUSSIAN KNAPWEED Acroptilon repens ACRE Bract margins papery, NOT spiny Upper leaves narrow and entire Donaldson Stems openly branched Lower leaves lobed Creeping knapweed Roadsides, riverbanks, ditches, pastures, waste places Rhizomatous perennial July to fall Cut or mow prior to seed set to reduce current year s growth; chemical control is needed Nevada-YES; California-YES, B-rated Height: 1-3 ft, generally 2-3 ft Stems: erect, cobwebby Leaves: upper, entire; lower and rosette, lobed Growth form: thick rounded clumps with drooping branches Root: black below crown Flower color: pink to purple 20 21

13 SPOTTED KNAPWEED Centaurea maculosa CEMA4 Bract tips dark, finely fringed, spineless Donaldson Upper leaves narrow and entire None Disturbed soil, rangelands, pastures, meadows, roadsides, areas with summer rainfall Perennial; sometimes biennial Early July to early September Minimize seed production by cutting or mowing; dig, removing top 2-6 in of root; herbicides are available Nevada-YES; California-YES, A-rated Lower leaves deeply lobed and smooth Note leaf placement Stems openly branched Height: 1-5 ft; generally closer to 3 ft Stems: erect and rough Leaves: upper, linear; lower, divided Growth form: tall with open branching Flower color: pink to purple

14 YELLOW STARTHISTLE Centaurea solstitialis CESO3 Long spines at tips of bracts (up to 1 in long) Donaldson Upper leaves entire Lower leaves deeply lobed None Roadsides, waste areas, grasslands Annual Late June to September Pull, dig or mow at first sign of yellow flowers; herbicides are available Nevada-YES; California-YES, C-rated Height: ft, commonly 2 ft Stems: winged Leaves: gray and hairy; upper, entire; lower, deeply lobed Growth form: stiffly branching Flower color: yellow 24 25

15 ASTER Aster spp. ASTER Native Look-alike Bracts do not have spines Donaldson Leaves narrow and entire Various Native Meadows, gardens Annual or perennial Late July to fall Desirable native plant; do not disturb Nevada-NO; California-NO Height: variable, often 1-2 ft Stems: smooth to hairy Leaves: upper and lower leaves narrow and entire Growth form: ranges from short to tall Flower color: variable, often pink to purple with yellow center 26 27

16 BACHELOR BUTTONS Centaurea cyanus CECY2 Nonnative Look-alike Bract tips pale, finely fringed, spineless Donaldson Leaves narrow and entire; generally not toothed except lower leaves Cornflower Nonnative, can be invasive, has escaped from cultivation Disturbed grasslands, open woods, ornamental plantings Annual July to September Mechanical controls (pull, dig, hoe); herbicides are available Nevada-NO; California-NO Height: up to 3 ft Stems: erect and branching Leaves: grayish and hairy; upper and lower leaves narrow and entire Growth form: tall, bushy Flower color: multicolored (white, blue, purple, pink, red) 28 29

17 HOARY CRESS Cardaria draba CADR Single stem Donaldson Tiny 4-petaled flowers in dense clusters near ends of branches 2 lobes clasp stem on upper leaves Leaves lance-shaped Whitetop, short whitetop Meadows, fields, roadsides, ditches, streambanks, rangelands Rhizomatous perennial May to June Mow two to three times per year at bud stage to slow spread; do not pull, as plants will grow from root fragments; chemical control is needed Nevada-YES; California-YES, B-rated Height: up to 2 ft, commonly 1 ft Stems: single stem gives rise to one flower cluster Leaves: blue-green foliage; upper leaves clasp stem; lower leaves petiolate Flower color: white

18 PERENNIAL PEPPERWEED Lepidium latifolium LELA2 multiple branches Donaldson Tiny 4-petaled flowers in dense clusters near ends of branches Leaves lance-shaped; leaf margins smooth or toothed Stems branch from juncture of leaf with main stem Tall whitetop Riparian areas, floodplains, meadows, seasonally wet areas, roadsides Rhizomatous perennial Late June to August Do not pull, dig, or cut the roots, as this may stimulate new growth; chemical control is needed Nevada-YES; California-YES, B-rated Height: 1-6 ft, commonly 3+ ft Stems: multiple branches grow from each stem Leaves: upper leaves, sessile; lower leaves, petiolate; basal leaves, much larger than upper leaves Flower color: white

19 WHITE SWEETCLOVER Melilotus alba MEAL12 Nonnative Look-alike Brenneman Pea-shaped flowers Many small fragrant flowers borne on irregular spikes at the ends of elongated stems Leaves consist of 3 leaflets, margins finely toothed None Nonnative, used in soil stabilization mixes Roadsides, waste areas Annual to biennial June to August Hand pull wearing gloves; dig or mow prior to seed set; herbicides available Nevada-NO; California-NO Height: 2-6 ft, commonly about 3-5 ft Leaves: 3 leaflets Stems: well-branched and coarse Flower color: white

20 YARROW Achillea millefolium ACMI2 Native Look-alike Flower heads flattened, dome-shaped corymbs Plant, Brenneman; Flower, Donaldson Leaves hairy and very finely pinnately divided, appearing feather-like Common yarrow, milfoil Native and introduced, can be invasive Gardens, meadows, grasslands, forests Perennial June to September Dig, removing as much root as possible; forms dense mat if mowed; chemical control is available Nevada-NO; California-NO Height: 2-3 ft Stems: hairy-wooly Leaves: feather-like; evenly distributed along stem; lower leaves larger Flower color: white or pink

21 DALMATIAN TOADFLAX Linaria dalmatica LIDA Spurs long, somewhat curved or straight Leaves ovate, tips pointed Donaldson Flowers borne in axils of upper leaves and bracts Wild snapdragon Roadsides, pastures, rangelands, cultivated fields Perennial July to fall Pull or dig for several years, removing as much root as possible; do not mow; chemical control is available Nevada-YES; California-YES, A-rated Leaves clasp stem Height: up to 3 ft Stems: erect and branched Leaves: ovate, alternate and entire; succulent and waxy Growth form: more scattered than yellow toadflax Flower color: yellow, with orange, bearded throat 38 39

22 YELLOW TOADFLAX Linaria vulgaris LIVU2 Plant, Brenneman; Flower, Charles Webber CA Academy of Sciences Spur Leaves linear, pointed at both ends Leaves alternate, crowded close together Butter and eggs Rangelands, roadsides, waste places, cultivated fields Perennial July to fall Pull or dig for several years, removing as much root as possible; do not mow; chemical control is available Nevada-YES; California-NO Height: 1-2 ft; shorter than dalmatian toadflax Leaves: linear, smooth to sparsely hairy; succulent and waxy Growth form: tends to grow in crowded patches Flower color: yellow, with orange, bearded throat 40 41

23 SNAPDRAGON Antirrhinum majus ANMA3 Nonnative Look-alike Flowers in terminal racemes Plant, Brenneman; Flower, 2003 Tony Morosco No spur Upper leaves long and narrow Lower leaves lanceolate None Nonnative Ornamental gardens Annual to perennial June to fall None; recommended garden flower Nevada-NO; California-NO Height: ft Leaves: upper, long and narrow; lower, lanceolate; soft, not waxy Flowers: fuzzy-hairy Flower color: yellow, but other colors are available 42 43

24 OXEYE DAISY Leucanthemum vulgare LEVU Leaves spoon-shaped Upper leaves toothed, sessile; smaller towards top of stem Approximate disk flower to ray flower ratio Donaldson Rosette leaves spatulate; margins crenulate Lower leaves pinnately lobed or toothed White daisy Meadows, roadsides, waste places, gardens Perennial June to August Pull or dig before seed production; herbicides are available Nevada-NO; California-NO Height: ft Stems: smooth to slightly hairy Leaves: upper, toothed and sessile; lower, pinnately lobed or toothed Flowers: single flower heads grow at ends of branches; bracts are lined in black Flower color: white with yellow center

25 SHASTA DAISY Leucanthemum X superbum LESU49 Nonnative Look-alike Plant, Brenneman; Flower, Donaldson Approximate disk flower to ray flower ratio Upper leaves serrate and sessile; smaller toward top of stem Rosette leaves oval; margins serrate None Nonnative, naturalized Well-drained soil, full sun, ornamental gardens Perennial July to September None; recommended garden flower Nevada-NO; California-NO Height: 1-3 ft, tends to be 6-12 in; taller than oxeye daisy Stems: stiff, more-or-less smooth Leaves: upper, serrate and sessile; lower, petiolate Flowers: single flower heads grow at ends of branches; heads larger than oxeye daisy Flower color: white with yellow center 46 47

26 KLAMATHWEED Hypericum perforatum HYPE 5 separate petals Occasional tiny black dots at edges of petals Flat-topped cymes 1 in Brenneman Transparent dots on leaves St. John s Wort Pastures, meadows, roadsides, waste areas Perennial June to late September Pull or dig repeatedly; chemicals are available Nevada-YES; California-YES, C-rated Height: 1-3+ ft Stems: erect with numerous rust-colored branches Branches: somewhat 2-ridged and woody at the base Leaves: elliptic to oblong, entire, opposite, sessile; not over 1 in long Flower color: yellow

27 SCOTCH BROOM Cytisus scoparius CYSC4 Numerous showy pea-like flowers Flattened, hairy, brown to black seed pods Upper leaves simple and entire Donaldson Lower leaves 3 leaflets, hairy None Pastures, forests, waste areas Perennial June to August Cut stems at ground level in late summer; pull seedlings; dig plants; use weed wrench to remove root; herbicides are available Nevada-NO; California-YES, C-rated Branches: many leafless or have few leaves Height: woody shrub up to 10 ft Stems: hairy when young, then generally smooth; most sharply 5-angled or ridged Branches: dark green; more-or-less erect Leaves: upper, simple and entire; lower, 3 leaflets, hairy Flower color: pale to deep yellow 50 51

28 GLOSSARY GLOSSARY Alternate: Borne singly at each node, such as leaves. Axil: The point formed between the stem and any part, such as a leaf, attached to it. Bract: A modified leaf at the base of a flower. Corymb: A flat-topped or round-topped arrangement of flowers where the lower flower stalks are longer than the upper stalks. Cyme: A flat-topped or round-topped arrangement of flowers in which the terminal flower blooms first. Crenulate: Having very small, rounded teeth on the leaf margin. Disk flower: The tiny, tubular flower of the Asteraceae that forms the center disk of the flowerhead. Divided: Deeply lobed leaf in which lobes are indented to the base or the midrib. Elliptic: Shaped like an ellipse or a narrow oval, broadest in the middle. Entire: The margins are smooth, without teeth or lobes. Inflorescence: A flower cluster. Linear: Narrow and flat with sides or edges parallel, as in a leaf. Lobed: Bearing lobes cut less than halfway to base or midvein. Margin: The outer edge of the leaf, which may be smooth, serrated, lobed, etc. Midrib: The middle vein of a leaf. Oblong: Leaf shape in which the leaf is two to four times longer than it is wide, with nearly parallel sides. Opposite: Leaves or other structures borne across from each other at the same node. Ovate Leaf: Egg-shaped leaf that is attached at the broad end. Panicle: A branched inflorescence in which the flowers bloom from the bottom up. Petiole: The stalk of a leaf. Pinnate: A compound leaf with leaflets arranged on opposite sides of the axis. Raceme: A simple, elongated arrangement of flowers. Ray flower: The long, narrow flower that radiates outward from the disk flower in the Asteraceae family. Each ray flower resembles a single petal. Rhizomatous: Having rhizomes, or horizontal underground stems that produce shoots above and roots below. Rosette: A dense, basal cluster of leaves arranged in a circular fashion around one point, usually at ground level. Serrate: With sharp teeth directed forward; generally refers to leaf edges. Sessile: Without a stalk of any kind; for example, a leaf directly attached to a stem. Spatulate: Shaped like a spatula, with a rounded blade that tapers to the base. Spike: An unbranched, long flower stalk in which the flowers attach directly to the stem and mature from the bottom upwards. Toothed: Having sharp points or lobes along a margin, as on a leaf. Umbel: A flat-topped flower arrangement. Winged stem: A stem with one or more thin, flat margins protruding along the length of the stem

29 WEED MAPPING CONTACT INFORMATION The Lake Tahoe Basin Weed Coordinating Group has been mapping weeds in the basin since Regular mapping and inventory helps us determine which species are present in the basin, what management methods are appropriate, and whether management has been a success. We can also track patterns of spread and plan preventive practices. We welcome your mapping information. Please include: the date surveyed the weed name and code (preferably the scientific name) the latitude and longitude of the observation if available. If using a global positioning system (GPS) unit, set your meter to datum NAD83 and decimal degrees. 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 Nevada Douglas County Weed District (775) Washoe County Weed Hotline (775) California Nevada County Agriculture Department (530) Placer County Agriculture Department (530) El Dorado County Agriculture Department (530) Funded by: The Lake Tahoe License Plate Program, Nevada Division of State Lands Nevada Department of Agriculture Please do not take any management actions or remove plants until they have been positively identified. Consult your county weed contact for assistance. Forward the data to the appropriate county. See listings on next page