Burke: Myriophyllum spicatum vs. Myriophyllum pinnatum

	Myriophyllum spicatum	Myriophyllum pinnatum
	Eurasian water milfoil, spiked water milfoil	cutleaf water-milfoil
Habit	Perennial, aquatic herbs, the stems simple or branched.
Leaves	Leaves 1-3 cm. long, in whorls of 3-4, pinnately dissected into 13-23 filiform segments, abruptly reduced to the bract-like leaves of inflorescences.
Flowers	Inflorescence emergent, simple; flowers single, subtended by bracts no longer than the fruit, the bracts serrulate to entire; sepals 4, attached to the top of the inferior ovary; petals 4, 2.5 mm. long, quickly deciduous; stamens 8 on the staminate flowers; stigmas short-hairy on the pistillate flowers.
Fruits	Achene 2.5 mm. long, rounded.

	Myriophyllum spicatum	Myriophyllum pinnatum
Flowering time	April-October	June-August
Habitat	Ponds, lakes, and quiet streams.	Lakes, sloughs, ditches, slow streams.
Distribution	Occurring on both sides of the Cascades crest in Washington; British Columbia to California, east across most of North America to the Atlantic Coast. [WildflowerSearch map] [BONAP county map]	Occurring west of the Cascades crest in Washington, where known only from Thurston County; southern British Columbia to Oregon, also in eastern North America. [WildflowerSearch map] [BONAP county map]
Origin	Introduced from Eurasia	Native
Conservation status	Not of concern	Not of concern
Sibling taxa	M. aquaticum, M. heterophyllum, M. hippuroides, M. pinnatum, M. quitense, M. sibiricum, M. spicatum × M. sibiricum, M. ussuriense, M. verticillatum	M. aquaticum, M. heterophyllum, M. hippuroides, M. quitense, M. sibiricum, M. spicatum, M. spicatum × M. sibiricum, M. ussuriense, M. verticillatum
Web links	Local floras: BC, CA, OR, WA Local Web sites: CalFlora, CalPhotos, Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search	Local floras: BC, OR, WA Local Web sites: Flora NW, PNW Herbaria WildflowerSearch iNaturalist (observations) USDA Plants Database LBJ Wildflower Center SEINet Plants of the World Online Encyclopedia of Life Wikipedia Google Image Search

Myriophyllum spicatum

Myriophyllum pinnatum

Eurasian water milfoil, spiked water milfoil

cutleaf water-milfoil

Habit

Perennial, aquatic herbs, the stems simple or branched.

Leaves

Leaves 1-3 cm. long, in whorls of 3-4, pinnately dissected into 13-23 filiform segments, abruptly reduced to the bract-like leaves of inflorescences.

Flowers

Inflorescence emergent, simple;

flowers single, subtended by bracts no longer than the fruit, the bracts serrulate to entire;

sepals 4, attached to the top of the inferior ovary;

petals 4, 2.5 mm. long, quickly deciduous;

stamens 8 on the staminate flowers;

stigmas short-hairy on the pistillate flowers.

Fruits

Achene 2.5 mm. long, rounded.

Myriophyllum spicatum

Myriophyllum pinnatum

Flowering time

April-October

June-August

Habitat

Ponds, lakes, and quiet streams.

Lakes, sloughs, ditches, slow streams.

Distribution

Occurring on both sides of the Cascades crest in Washington; British Columbia to California, east across most of North America to the Atlantic Coast.

[WildflowerSearch map]

[BONAP county map]

Occurring west of the Cascades crest in Washington, where known only from Thurston County; southern British Columbia to Oregon, also in eastern North America.

[WildflowerSearch map]

[BONAP county map]

Origin

Introduced from Eurasia

Native

Conservation status

Not of concern

Sibling taxa