Burke: Myriophyllum spicatum vs. Myriophyllum aquaticum

	Myriophyllum spicatum	Myriophyllum aquaticum
	Eurasian water milfoil, spiked water milfoil	parrot's feather, water feather, South American water milfoil
Habit	Perennial, aquatic herbs, the stems simple or branched.	Perennial, aquatic herbs, the stems sturdy, 2-4 mm. thick and 1-9 dm. long, completely submerged until time of flowering.
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.	Leaves in whorls of 4-6, all finely pinnatifid, 2.5- 5 cm. long, the 25-37 divisions filiform; stipules linear.
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.	Flowers in the axils of submerged leaves along the main stem, with minute, linear to filiformly dissected bracteoles; sepals 4, attached to the top of the inferior ovary; staminate flowers with 4 small petals and 8 stamens; pistillate flowers with no petals, the stigmas plumose.
Fruits	Achene 2.5 mm. long, rounded.	Achene 1.5-2 mm. long.

	Myriophyllum spicatum	Myriophyllum aquaticum
Flowering time	April-October	May-July
Habitat	Ponds, lakes, and quiet streams.	Ponds and slow-moving 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 on both sides of the Cascades crest in Washington; British Columbia to California and Idaho, east across the southwest to central and eastern North America. [WildflowerSearch map] [BONAP county map]
Origin	Introduced from Eurasia	Introduced from South America
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. heterophyllum, M. hippuroides, M. pinnatum, 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, 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

Myriophyllum spicatum

Myriophyllum aquaticum

Eurasian water milfoil, spiked water milfoil

parrot's feather, water feather, South American water milfoil

Habit

Perennial, aquatic herbs, the stems simple or branched.

Perennial, aquatic herbs, the stems sturdy, 2-4 mm. thick and 1-9 dm. long, completely submerged until time of flowering.

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.

Leaves in whorls of 4-6, all finely pinnatifid, 2.5- 5 cm. long, the 25-37 divisions filiform;

stipules linear.

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.

Flowers in the axils of submerged leaves along the main stem, with minute, linear to filiformly dissected bracteoles;

sepals 4, attached to the top of the inferior ovary; staminate flowers with 4 small petals and 8 stamens; pistillate flowers with no petals, the stigmas plumose.

Fruits

Achene 2.5 mm. long, rounded.

Achene 1.5-2 mm. long.

Myriophyllum spicatum

Myriophyllum aquaticum

Flowering time

April-October

May-July

Habitat

Ponds, lakes, and quiet streams.

Ponds and slow-moving 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 on both sides of the Cascades crest in Washington; British Columbia to California and Idaho, east across the southwest to central and eastern North America.

[WildflowerSearch map]

[BONAP county map]

Origin

Introduced from Eurasia

Introduced from South America

Conservation status

Not of concern

Sibling taxa