Invasive Aquatic Plants Identifying Known & Potential Weeds in the PNW

Oregon Lake Watch

Center for Lakes and Reservoirs

Overview

• Impacts – why aquatic weeds matter?

• Growth forms – Submerged

– Floating-leaf

– Emergent (shoreline)

• Aquatic plants, including – Common invasives

– New (high priority) invasives

– Common native look-alikes

• Importance of confirmation & reporting

Ecological Impacts

• Reduce light penetration & mixing

• Reduce species diversity

• Alter temperature, dissolved oxygen & pH

• Degrade fish habitat

• Altered nutrient cycling

Economic Impacts

• Reduce flow in irrigation canals and drainage ditches

– Increased cost of irrigation

– Flooding

– Clogged pumps & intake structures

• Loss of recreational resources

• Negative impacts on property values

Photo: Enviroscience, Inc Photo: Bridgetotrade.net

Human Health and Safety

Growth forms

How do aquatic weeds move and

spread?

Invasive plants and animals have

spread to new areas due to:

boats and trailers

bait buckets

water movement (waves, downstream movement)

waterfowl & other animals

Aquatic plants can reproduce & spread by:

Osceola County, Hydrilla Dem. Proj.

Rich Miller, PSU-CLR

www.birdphotos.com

PSU-CLR

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seed plant fragments tubers turions

Submerged

Aquatic Plants

Eurasian watermilfoil

(Myriophyllum spicatum)

a.k.a. “EWM”

EWM Habitats & Growth

• Lakes, reservoirs, ponds, rivers, and streams

• Fresh to brackish water (up to 15 ppt)

• Depth: (0.5) 1-5 (10) meters

• pH range: 5.4 to 11

• Fine-textured, inorganic sediment

• Early & rapid spring growth (water temp >15 ͦ C )

• Tops out in water < 5 m

• Autofragmentation in fall/early winter

• Overwintering root crowns

Northern watermilfoil

(M. sibiricum)

Whorled watermilfoil

(M. verticillatum)

Andean watermilfoil

(M. quitense)

J. Parsons, WA DOE

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Other Myriophyllum spp.

Identification of Eurasian milfoil

• 4 leaves per whorl

• 14 or more leaflet pairs

• leaves more squared in

outline

• collapse more when out of

the water

• no winter buds

Variable-leaf watermilfoil

(M. heterophyllum)

Hybrid watermilfoil

(M. spicatum × sibiricum)

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Milfoil Character Comparison

submerged leaves

Status in PNW # leaflet pairs leaf size leaves/whorl emergent leaves (bracts) winter buds (turions)

Northern watermilfoil

(Myriophyllum sibiricum) NATIVE <14 (5-14) < 4 cm long 3 to 5

reduced (1-3 mm long);

smaller than flowers yes

whorled watermilfoil

(Myriophyllum

verticillatum)

NATIVE <14 (5-14) < 5 cm long 4 to 5 2-10 mm long;

deeply pinnately lobed yes

Andean watermilfoil

(Myriophyllum quitense) NATIVE 5-10

1.5 - 4 cm

long 2 to 5

0.5-1 cm long;

partially toothed yes

Parrot feather

(M. aquaticum) INVASIVE 10-15

1.5 - 3.5 cm

long 3 to 6

2-5 cm long; 16-18 leaflet

pairs

stiff, waxy, bright green

no

Eurasian watermilfoil

(M. spicatum) INVASIVE > 14 (12-24) 2 - 4 cm long 3 to 6

reduced (1-3 mm long);

smaller than flowers no

Variable-leaf watermilfoil

(M. heterophyllum) INVASIVE 5-12 2-4 cm long 4 to 6

0.5 - 3 cm long;

larger than flowers;

serrated/lobed

yes

Hybrid watermilfoil

(M. spicatum × sibiricum) INVASIVE 8-19

1.5-4.2 cm

long ? ? ?

Hydrilla verticillata

(hydrilla)

Hydrilla Distribution

• Map of ID and WA and

• eddmapp

EDDMapS. 2012. Early Detection & Distribution Mapping System. The University of Georgia - Center for Invasive Species

and Ecosystem Health.

Primarily

dioecious

Monecious

Dioecious

Other Hydrocharitaceae

Elodea canadensis

(Canadian waterweed) Elodea nutallii

(Nuttall’s waterweed)

Egeria densa

(Brazilian elodea)

Elodea sp.

(Native)

Egeria

(Non-native,

common in OR/WA)

Hydrilla

(Non-native,

unknown in OR)

Differentiating the Hydrocharitaceae

Robert Vidéki, Doronicum Kft.,

Bugwood.org

Potamogeton crispus

(curly leaf pondweed)

Sastramoutomo 1981

Stuckenia pectinatus

(sago pondweed)

Other Potamogetonaceae

Potamogeton foliosus

(leafy pondweed)

P. pusillus

(small pondweed)

Potamogeton richardsonii

(Richardson’s pondweed)

© 2005, Ben Legler © 2005, Ben Legler

Potamogeton robbinsii

(Robbins' pondweed)

© 2012, Craig Althen

Zannichellia palustris

(horned pondweed)

© 2005, Ben Legler

Ceratophyllum demersum

(coontail, hornwort)

• Whorled leaves

• Serrated margins

• Horn-like divisions

Cabomba caroliniana

(Carolina fanwort)

Ranunculus aquatilis

(white water buttercup)

© 2004, Ben Legler

Isoetes spp. (quillworts)

Isoetes occidentalis

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Isoetes nuttallii

Utricularia vulgaris

(common bladderwort)

Utricularia inflata

(swollen bladderwort)

Utricularia spp. (bladderworts)

Callitriche palustris

(vernal water-starwort) Callitriche hermaphroditica

(northern water-starwort)

Callitriche heterophyllum

(different-leaved water-starwort)

Callitriche stagnalis

(pond water-starwort)

Macroalgae

Chara spp. (muskgrasses)

Nitella spp.

(brittlewort) Chara

• 6-16 branchlets,

never divided;

musky scent, tiny

thorn-like

projections

Nitella

• 6-8 evenly

forked branchlets;

no scent; smooth

texture

Floating Leaf

Aquatic Plants

Nymphaea odorata

(fragrant water lily)

• Rooted aquatic perennial

• 3-6 feet

• Floating heart-shaped or circular leaves (30 cm); purplish underneath, leathery, deeply cordate

• Large (6-12 cm) fragrant flowers; 20-30 petals, range of colors with yellow centers

Nuphar lutea

(yellow pond-lily )

• Larger, oval to heart-shaped

leaves with a prominent

midvein

• Flowers – yellow petals

and centers, 9-petals

Nymphoides peltata

(yellow floating heart)

• Aquatic perennial

• Depths of 2-13 feet.

• Leaves heart-shaped to circular, 1 to 4 in long, purplish underneath with slightly wavy margins

• 5-petaled, 1-1.25” diameter

© 2004, Sue Winterowd:

Brasenia schreberii

(water shield)

Eichhornia crassipes

(water hyacinth)

Ludwigia hexapetala, L. peploides

(water primrose)

Ludwigia palustris

(marsh seedbox)

© 2005, Ben Legler

Azolla pinnata (feathered water fern)

Other azollas

A. filliculoides A. mexicana

Emergent

Aquatic Plants

Aquatic perennial

Moving down Columbia River from infestation in Montana

Large infestation in Yakima River

Butomus umbellatus

(flowering rush)

Butomus umbellatus

(flowering rush)

• Cluster of 20-50 flowers

with 3 pinkish petals and

sepals.

• Leaves triangular at base,

flattened above, but

strong mid-rib.

• Emergent leaf tips may be

spirally twisted

• Submersed leaves long,

strap-like.

• Strongly rhizomatous

Phragmites australis

(common reed)

ssp. americanus ssp. australis

Phragmites Distribution in the Columbia

Basin

Green = native

Red = introduced

Warrenton, OR

Typha spp. (cattail)

T. latifolia

(broad-leaf cattail)

T. angustifolia

(narrow-leaf cattail)

Invasives

Lythrum salicaria

(purple loosestrife) Lysimachia vulgaris

(garden loosestrife)

Phalaris arundinacea

reed canary grass

ribbon grass

Iris pseudacorus (yellow-flag)

Myrophyllum aquaticum

(parrot feather) Hippuris vulgaris

(common mare’s tail)

Importance of Reporting &

Confirmation

Many factors can complicate accurate

identification, such as:

• confusion with closely-related native species

• hybrids (milfoils, pondweeds, etc.);

• plasticity – physical characteristics (leaf shape

or color) may vary due to environmental

conditions

Suspected weeds should be

reported ASAP! Delayed reporting/confirmation can result in:

higher management costs

reduced chances of eradication

(Rejmanek and Pitcairn, 2002)

Remember, weeds are not alone out there!

Zebra and Quagga mussels

Dreissena sp.

REPORT THIS SPECIES ASAP!

• The name derives from stripes on the

shell…

• However you won’t always see black and

white stripes

Report Suspected AIS

www.pdx.edu/oregon-lake-watch

503-725-2937 or 503-725-9075

oregoninvasiveshotline.org

or call 1-866-INVADER