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Responding to Horticulture InquiriesWeeds/Invasive plants

Mark Renzmrenz@wisc.edu

fyi.uwex.edu/weedsci

Dutchman’s breeches battling garlic mustard

WEATHER DRIVES PLANT POPULATION DEVELOPMENT

Extended fall growing season

What species do well when we have extended fall?

• Perennial species that continue to grow until a hard freeze

– Lawns: Creeping charlie

– Pastures/grasslands: Canada thistle

– Forests/natural areas: Buckthorn/honeysuckle

• Biennials

– Burdock, wild parsnip, garlic mustard

• Winter Annuals (if we get september precip.)

– Chickweed, Shepard's purse

• Ample in fall

• Above average in spring

What about Precipitation?

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Which winter annuals to look for?

Chickweed Identification

• 11 species present in WI, 

– some difficult to differentiate

• Opposite, small leaves

• Emerges in cool weather

• Creates mats of plants

Shepherd’s purse

•Plants have mostly rosette leaves

•Leaves lobed

•Stem is elongated stalk with few leaves

•Flowers have four white petals

•Seed pod small; triangular shape

•Like a true “shepherd’s purse”

Shepherd’s purse

Field pennycress

•Entire plant has odor of garlic

•Leaves with wavy margins

•Leaves have ear-like lobes that clasp stem on upper leaves

•Flowers have four white petals

•Seed pods size of dime, notched on the top

Field pennycress

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Horseweed (Conyza canadensis)

Horseweed/Marestail

Typical start to 2017!

How many have heard about “superweeds”?

• More competitive

• Increased risk for herbicide resistance– Multiple herbicides

• Pigweeds are of greatest concern– Palmer amaranth

– waterhemp

Pigweed species (Amaranthus) found in Wisconsin

• 13 species, 6 of agricultural importance

1. Red‐root pigweed (60 counties#)2. Smooth pigweed (14 counties#)3. Prostrate pigweed (48 counties#)4. Powell’s amaranth (34 counties#)

5. Common/tall waterhemp (50 counties*)6. Palmer Amaranth (4 counties*)

# herbarium reports used to determine presence* Added to herbarium reports from knowledge from credible sources

All Pigweeds have notches in tips of young leaves

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Start with the stem when differentiating pigweeds.Hairy: redroot pigweed, smooth pigweed, Powell amaranth

Smooth: waterhemp, Palmer amaranth, spiny amaranth

Pigweed id

Palmer vs Waterhemp

Both have notched leaves at seedling stage

Subtle but important differences in leaf morphology

Palmer: leaf is more rounded or egg-shaped; petiole generally longer than leaf

Waterhemp: leaf is longer; petiole shorter than leaf

Palmer, waterhemp, redroot

Seed heads can be used for identification later in the season.

Palmer: Long terminal seed heads

Waterhemp: Thin, wiry seed heads

Summary of Pigweed ID

• Step 1: smooth or hairy stems

– If smooth Palmer or waterhemp or spiny amaranth

– If ANY hairs, redroot or smooth (others)

• Step 2 petiole longer than leaf

– If yes PALMER

• confirm by leaf shape (more rounded) and inflorescence, long with one main stem> 1 ft long when mature

– If no waterhemp– Confirm by leaf shape (narrow) and twice divide inflorescences (each inches long)

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diecous diecous

Few hairs

Palmer Amaranth Waterhemp

D. Stoltenberg, D Hammer, N Drewitz

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What is the distribution in Wisconsin of these two species?

WI herbarium results + other credible reports

Actively surveyed for new populations in 2016!

• Statewide we did not observe an increase in the presence of waterhemp or Palmer in Wisconsin

• Waterhemp: 5.0 % of fields  statewide– 10% in the following counties

• Northcentral counties: Clark, Marathon• Northwest counties: Polk, Barron• Central counties: Portage, Adams• Southcentral counties: Columbia, Dane, Jefferson, Dodge

• Populations of Palmer amaranth continue to be extremely rare (<1%)– Proactive monitoring will be needed to detect

Will be developing outreach material and will be asking for you to report pigweed species this summer!

Resources UWEX will point you to for weed identification

• GENERAL RESOURCES

– Weed ID Website: http://weedid.wisc.edu

– Weeds of the Northeast (book)

– Weeds of Ontario (book)

• INVASIVE PLANTS

– DNR NR40 Guide (field guide)

– Invasive Plant videos (my website/YouTube)

– Invasive plant factsheets (learning store/my website)

Invasive plantsWild Chervil

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What is an invasive species?

4 main points

URL: WIFDN INVASIVE SPECIES INTRO

http://docs.legis.wisconsin.gov/code/admin_code/nr/001/40.pdf

What is an invasive plant?

• A non‐native plant that causes economic, environmental impact to WI or harm to human health

• We have an invasive species rule that regulates invasive species (NR:40)

– Updated (May 2015)

– Over 130 plants regulated to some degree

Are all non‐native species invasive?

Estimated 1% of introduced species become invasive (Groves 1986)

A few bad actors 

What is the legal definition of an invasive species?

• NR 40, WI‐DNR (2009): A nonnative species including hybrids, cultivars, subspecific taxa, and genetically modified variants whose introduction causes or is likely to cause economic or environmental harm or harm to human health”

http://docs.legis.wisconsin.gov/code/admin_code/nr/001/40.pdf

How WI‐DNR regulates

• Prohibited

– Control required

– Illegal to knowingly spread

• Restricted

– Control encouraged

– Illegal to knowingly spread

• Split listed

– Category changes depending on location in state

How many are regulated?

• 68 prohibited species

– Yellow star thistle

– Kudzu (not in WI)

• 63 restricted species– Wild parsnip

– Common buckthorn

– Garlic mustard

• 14 split listed– Hill mustard

– Eurasian marsh thistle

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SOME ornamental are invasive

Japanese Barberry in WI Natural Area

INFORMING CONSUMERS ABOUT BETTER CHOICES

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HOW TO GET THE (FREE!) APP

INVASIVE ORNAMENTALS IN WI

Common Name Common Name

Buckthorn spp. Crown vetch

Honeysuckle spp (several) Purple loosestrife

Autumn olive Japanese knotweed

Black locust Yellow iris

Japanese barberry Lilly of the valley

Multiflora rose Orange daylillys

Oriental bittersweet White poplar

Dame's rocket Common Periwinkle

Phragmites Tree of heaven

Reed canarygrass Burning bush

Citizen Science to Detect Invasive Species

Anne Pearce anne.pearce@wisc.edu; 608‐262‐9570

fyi.uwex.edu/wifdn

Wisconsin First Detector Network

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What is WIFDN?

• Statewide citizen science network

• Provide educational resources

• Support volunteer opportunities

Education and Training

• Website resources fyi.uwex.edu/wifdn• In person workshops• Annual webinar series (Fridays, noon – 1:30 

pm)

•March 17th: What to Look for in 2017•April 7th: Passengers vs. Drivers•April 21st: Take Action! Control Efforts 

in Wisconsin•May 5th: Citizen Science + Volunteer 

Opportunities

Register at fyi.uwex.edu/wifdn

2016 Efforts

• 542 webinar + workshop participants

• 2978 volunteer hours

• 1800 invasive species reports

WIFDN volunteers work across the state

But which species do I report?

• Over 100 regulated invasive plants in WI

– More are not listed

• Invasions can be specific to areas of Wisconsin.

• Creating resources to assist in prioritizing which species to REPORT!

– Search for: Priority Invasive Plant Lists in Wisconsin

The Process of Creating a Priority Species List

Percent of county deemed “suitable habitat”

Priority LIST(top species)vs

High Priority LIST(top species with limited presence points)

ArcGIS Story Map

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We are asking for your help!!!!!

We create predictive models for habitat that CAN be invaded from 

reports!Leafy spurge predictive map

Report new infestations

Several options on how to report1. Contact me, DNR staff, county agent

2. Submit observation via the Great Lakes Early Detection Network/WIFDN

– Visit fyi.uwex/edu/wifdn for training info on how to report• Website

• Smartphone app (free)

Join now and help inform us about the potential future spread of new invaders!

Thank you!fyi.uwex.edu/weedscimrenz@wisc.edu