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Vascular Plants of California
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Myriophyllum spicatum
EURASIAN WATER-MILFOIL


Higher Taxonomy
Family: HaloragaceaeView Description 
Common Name: WATER-MILFOIL FAMILY
Habit: [Annual, shrub] perennial herb, generally aquatic or semiterrestrial, dioecious or monoecious. Leaf: cauline, opposite, alternate or whorled; submersed blades pinnately divided, segments thread-like; emergent leaves simple, entire to divided. Inflorescence: raceme, spike, or panicle; flowers 1 or clustered, short-pedicelled to +- sessile. Flower: generally unisexual, small; calyx tube short, fused to ovary, lobes 2--4; petals generally 2--4; stamens 4 or 8, filaments generally short; ovary inferior, chambers 1--4, styles 2--4, separate, stigmas generally plumose. Fruit: fleshy or of nut-like mericarps, dehiscent or not. Seed: generally 1 per chamber.
Genera In Family: 6--8 genera, +- 100 species: especially southern hemisphere, some cultivated. Note: Haloragis erecta (Murray) Eichler not naturalized in California.
eFlora Treatment Author: Adolf Ceska & Oldriska Ceska
Scientific Editor: Bruce G. Baldwin.
Genus: MyriophyllumView DescriptionDichotomous Key


Common Name: WATER-MILFOIL
Habit: Plant from rhizomes, occasionally with overwintering buds (late in growing season); occasionally terrestrial. Stem: simple or branched, generally green. Leaf: submersed leaves generally whorled, 3--6 per node; emergent leaves entire to pinnately divided, occasionally bract-like. Inflorescence: generally emergent, spike-like, simple or branched, terminal, flowers in whorls. Flower: proximal pistillate, middle occasionally bisexual, distal staminate; calyx lobes 4; petals generally 4, ephemeral on staminate flowers, minute or 0 on pistillate flowers; stamens generally 8; ovary 4-chambered. Fruit: mericarps 4, nut-like.
Etymology: (Greek: many leaves, from leaf segments) Note: Myriophyllum specimens best collected in flower or fruit.
Unabridged Note: Plants should be washed first and then "floated" on the herbarium mounting paper in a shallow dish with water [see Ceska & Ceska 1987 Ann Missouri Bot Gard 73:825--827].
Reference: Ceska et al. 1986 Brittonia 38:73--81
Myriophyllum spicatum L.
NATURALIZED
Habit: Monoecious; winter buds 0. Stem: > 1 m, +- red to light green when dry. Leaf: submersed leaves < 3 cm, segments >= 28, < 10 mm, linear, angles, spacing uniform throughout leaf. Inflorescence: spike, 4--8 cm, emergent; bracts 1--3 mm, < flowers, lanceolate, entire to toothed.
Ecology: Uncommon. Ditches, lake margins; Elevation: < 2080 m. Bioregional Distribution: NCoRI, SNF, n SNH, GV, SnFrB, SCo, SnBr, PR, MP; Distribution Outside California: to British Columbia, eastern Canada, eastern United States; native to Eurasia, northern Africa. Flowering Time: Jul--Sep
Unabridged Note: Recognizable by large number of parallel leaf segments that stand in acute angles to rachis.
Jepson eFlora Author: Adolf Ceska & Oldriska Ceska
Reference: Ceska et al. 1986 Brittonia 38:73--81
Index of California Plant Names (ICPN; linked via the Jepson Online Interchange)
Noxious Weed listed on the CDFA Weed Pest Ratings table
View the CDFA Pest Rating page for Myriophyllum spicatum
Weed listed by Cal-IPC

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Citation for this treatment: Adolf Ceska & Oldriska Ceska 2012, Myriophyllum spicatum, in Jepson Flora Project (eds.) Jepson eFlora, https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=34276, accessed on April 20, 2024.

Citation for the whole project: Jepson Flora Project (eds.) 2024, Jepson eFlora, https://ucjeps.berkeley.edu/eflora/, accessed on April 20, 2024.

Myriophyllum spicatum
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©2009 Barry Rice

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Geographic subdivisions for Myriophyllum spicatum:
NCoRI, SNF, n SNH, GV, SnFrB, SCo, SnBr, PR, MP
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).





 

Data provided by the participants of the  Consortium of California Herbaria.
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All markers link to CCH specimen records. The original determination is shown in the popup window.
Blue markers indicate specimens that map to one of the expected Jepson geographic subdivisions (see left map). Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.
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CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa, if there are more than 1 infraspecific taxon in CA.
Blue line denotes eFlora flowering time (fruiting time in some monocot genera).