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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
© 2
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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