Characteristics to Identify Washington's Noxious Aquatic Weeds and Native Look-a-Likes

MILFOIL SPECIES

Myriophyllum aquaticum (parrotfeather) - Non-native plant

Emergent leaf stalks - very distinctive bright green foliage looks like tiny fir trees on the waters surface
Usually 5-8 leaves per whorl (arranged around the stem) 

Myriophyllum spicatum (Eurasian watermilfoil) - Non-native plant

Mature leaves with 14-24 leaflet pairs, at about a 45 degree angle to the length of the leaf
No winter buds produced
Floral bracts smaller than the flower

The following two native species are very similar in appearance to Eurasian watermilfoil:

Myriophyllum sibericum (northern milfoil) - Native plant look alike

Mature leaves with 4-14 leaflet pairs from a 45 degree angle to almost perpendicular to the leaf length
Cylindrical winter buds
Flower bracts smaller than the flower

Myriophyllum verticillatum (western milfoil) - Native plant look alike

Mature leaves with 9-17 leaflet pairs
Pinnate floral bracts, larger than the flower
Club-shaped winter buds

OXYGEN WEEDS OR WATERWEEDS

Egeria densa (Brazilian elodea) - Non-native plant

4 leaves per whorl, to 4 cm long
Minute serrations along the leaf edges, but you need magnification to see the serrations
Male flowers only, up to 2 cm across
No tubers

Hydrilla verticillata (hydrilla) - Non-native plant

5 leaves per whorl - less early in the season, 1-2 cm long
Visibly toothed leaf edges
Tiny flowers
Tuber present

Similar Appearing Native Species:

Elodea spp. (American waterweed) - Native plant look alike

3 leaves per whorl, usually less than 2 cm long
Need magnification to see the serrated leaf edges
Tiny flowers
No tubers

FANWORT

Cabomba carolineana (fanwort) - Non-native plant

Opposite fan-shaped leaves on long stalks
Small floating leaves are present when growing to the water surface

Similar Appearing Native Species:

Ranunculus aquatilis (water buttercup) - Native plant look alike
Fan-shaped alternate leaves

Megalodonta beckii (marsh marigold) - Native plant look alike
Fan-shaped opposite leaves, but the leaf stalks are so short that the leaves appear whorled. 

BLADDERWORTS

Utricularia inflata (swollen bladderwort) - Non-native plant

Radiating wheel-like float supports the flower stalk
Small coiled winter buds

Similar Appearing Native species:

Utricularia vulgaris (common bladderwort) - Native plant look alike

No float on the flower stalk
Large ball-shaped winter buds
When neither structure is present, these two species are extremely difficult to distinguish

LOOSESTRIFES

Lythrum salicaria (purple loosestrife) - Non-native plant

Pink/purple flowers with 6 sepals, 6 petals, 12 stamins
Fruit -a 2 valved capsule
Generally opposite leaves
Square stem
Reproduces by seeds and adventitious buds on buried stems (growth stimulated by disturbance)

Lysimachia vulgaris (garden loosestrife) - Non-native plant

Leaves opposite or whorled
Leaves soft-hairy, dotted with black or orange glands
Flowers showy and yellow, 5 petals, fruit is a dry capsule

WILLOW HERBS

Epilobium hirsutum (hairy willow-herb) - Non-native plant

Showy pink-red flowers with 4 sepals, 4 notched petals, 8 stamens
Round stem
Long seed capsules that split open and release the fuzzy coated seeds
Leaves are opposite and hairy, toothed

GRASSES

Phalaris arundinacia (reed canarygrass) - Likely exotic ecotype

To 6 feet tall, stem 0.5 inches wide
Leaves 0.25 to 0.75 inches wide

Phragmites austalis (common reed) - Likely exotic ecotype

To 12 feet tall
Sheath of the leaf blade is smooth and loose allowing leaves to twist in the wind
Flower spikes feathery

OTHER

Nymphoides peltata (yellow floating heart) - Non-native plant

4-6 inches across waterlily-like floating leaves with a slit 
Yellow flowers with 5 fringed petals, held above the water's surface

Ludwigia hexapetala (water primrose)

Yellow flowers with 5 sepals and 5 petals
Alternate leaves
Erect stems

Plant Identification Table of Contents | Return to Aquatic Plants and Lakes