Burke: Myriophyllum aquaticum vs. Myriophyllum hippuroides

	Myriophyllum aquaticum	Myriophyllum hippuroides
	parrot's feather, water feather, South American water milfoil	western milfoil, western water milfoil
Habit	Perennial, aquatic herbs, the stems sturdy, 2-4 mm. thick and 1-9 dm. long, completely submerged until time of flowering.	Perennial, aquatic herbs, the stems freely branched, 1-6 dm. long.
Leaves	Leaves in whorls of 4-6, all finely pinnatifid, 2.5- 5 cm. long, the 25-37 divisions filiform; stipules linear.	Leaves 4-5 per whorl, the submersed ones 1.5-3 cm. long, pinnately dissected into 13-23 filiform segments, and gradually transitional to the linear-oblong, 10-15 mm. long, serrate bracts.
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.	Inflorescence terminal, immersed to emersed, the flowers single in the axils of the bracts; sepals 4, attached to the top of the inferior ovary; petals 4, pale yellow, 1 mm. long; staminate flowers uppermost on the stem, stamens 4; stigmas very short, smooth.
Fruits	Achene 1.5-2 mm. long.	Achene 1.5-2 mm. long.

	Myriophyllum aquaticum	Myriophyllum hippuroides
Flowering time	May-July	May-October
Habitat	Ponds and slow-moving streams.	Ponds and slow-moving streams.
Distribution	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]	Occurring west of the Cascades crest and east in the Columbia River Gorge in Washington; British Columbia to California; introduced in Illinois. [WildflowerSearch map] [BONAP county map]
Origin	Introduced from South America	Native
Conservation status	Not of concern	Not of concern
Sibling taxa	M. heterophyllum, M. hippuroides, M. pinnatum, M. quitense, M. sibiricum, M. spicatum, M. spicatum × M. sibiricum, M. ussuriense, M. verticillatum	M. aquaticum, M. heterophyllum, 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 aquaticum

Myriophyllum hippuroides

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

western milfoil, western water milfoil

Habit

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

Perennial, aquatic herbs, the stems freely branched, 1-6 dm. long.

Leaves

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

stipules linear.

Leaves 4-5 per whorl, the submersed ones 1.5-3 cm. long, pinnately dissected into 13-23 filiform segments, and gradually transitional to the linear-oblong, 10-15 mm. long, serrate bracts.

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.

Inflorescence terminal, immersed to emersed, the flowers single in the axils of the bracts;

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

petals 4, pale yellow, 1 mm. long; staminate flowers uppermost on the stem, stamens 4;

stigmas very short, smooth.

Fruits

Achene 1.5-2 mm. long.

Myriophyllum aquaticum

Myriophyllum hippuroides

Flowering time

May-July

May-October

Habitat

Ponds and slow-moving streams.

Distribution

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]