Myosoton aquaticum
(L.) Moench
Common Name:
Giant chickweed
Synonyms and Other Names:
Cerastium aquaticum Linnaeus, Alsine aquatica (Linnaeus) Britton, Stellaria aquatica (Linnaeus) Scopoli, Malachium aquaticum, water chickweed
Identification:
This adventive perennial plant is 2"-24" tall, branching occasionally. The stems are erect or spreading, and more or less hairy. The opposite leaves are up to 2" long and 1" across. They are cordate-ovate, smooth along the margins, slightly pubescent, and usually sessile (the lower leaves may have short petioles). Single flowers may develop from the leaf axils of the upper stems, while the remaining flowers occur in small clusters at the end of stems. Each flower is about ½" across when it is fully open, consisting of 5 white petals that are cleft, 5 green sepals that are ovate and pubescent, 5 slender white styles, and 10 stamens. There is some variability across populations of plants regarding how deeply cleft the petals are. These petals are slightly longer to much longer than the sepals. The pedicel of each flower is conspicuously pubescent and up to 1" long. The blooming period occurs from late spring to late summer and lasts about 2-3 months. Each flower is replaced by a seed capsule that is ovoid and single-celled; it contains several seeds. Each seed is orbicular-reniform and minutely bumpy across the surface. The root system is fibrous and produces rhizomes, which enables this plant to form vegetative colonies.
Stems are 10-100 cm, minutely glandular-pilose distally. Leaf blades 2-3.5(-8.5); 1-2(-4.4) cm. Pedicels are 1-2(-3) cm, minutely glandular-pilose. Sepals are 4-6 mm, to 9 mm in fruit; petals 4-7 mm, mostly exceeding sepals. Capsules 5-10 mm, usually slightly exceeding calyx. 2n = 20(?) (Asia), 28 (Europe, Asia), 29 (Europe).
Size:
2-24 inches tall
Native Range:
Eurasia.
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This map only depicts Great Lakes introductions.
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Great Lakes Nonindigenous Occurrences:
Botanists began noticing M. aquaticum in the eastern United States in the late 19th century, particularly in port towns where solid ballast had been dumped (Brown, 1880; Robinson, 1903). The first Great Lakes sighting of M. aquaticum occurred in Lake St. Clair in 1894. This species now occurs in all Great Lakes states and provinces.
Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Myosoton aquaticum are found here.
Table last updated 4/25/2024
† Populations may not be currently present.
Ecology:
Habitats include wet to moist areas along streams, meadows, roadside ditches, pastures, and gardens. Water chickweed often occurs in degraded habitats, but can also be found in higher quality habitats growing alongside native flora. The preference is full sun to light shade, wet to moist conditions, and fertile soil that is loamy or silty. It can withstand dry conditions for short periods of time. It flowers from spring to fall.
Means of Introduction:
Unknown. Its presence outside the Japanese Pavillion at the Philadelphia Centennial Grounds in 1878 (Scribner 50 and 51, MO) suggests an escape from an intentional introduction.
Status:
Established.
Great Lakes Impacts:
Summary of species impacts derived from literature review. Click on an icon to find out more...
Current research on the environmental impact of Myosoton aquaticum in the Great Lakes is inadequate to support proper assessment.
This species may behave somewhat invasively but is generally considered to be of low concern: while it may compete for resources, it is often found growing side-by-side with native flora. There is little or no evidence to support that Myosoton aquaticum has significant socioeconomic impacts in the Great Lakes.
No socioeconomic impacts have been reported for this species.
There is little or no evidence to support that Myosoton aquaticum has significant beneficial impacts in the Great Lakes.
While other species may feed on the nectar and leaves of this plant, it does not provide notable benefits. Young leaves and stems are edible if cooked, but not of commercial value. The nectar of the flowers attracts small bees and Syrphid flies; some bees may collect pollen, while flies occasionally feed on pollen. The caterpillars of several moth species probably feed on the foliage, like other chickweeds. The seeds of chickweeds are attractive to sparrows and other birds, while the foliage is eaten by rabbits. Because water chickweed frequently occurs in wetland habitats, its foliage is probably eaten by the Canada goose.
Management:
Regulations (pertaining to the Great Lakes region)
There are no known regulations for this species. Note: Check federal, state/provincial, and local regulations for the most up-to-date information.
Control
Control options have not been very well documented for this species, though significant quantities of literature exist for management and control of other members of the chickweed family..
Biological
There are no known biological control methods for this species.
Physical
Mow before seeds form, reseed heavily infested areas with competitive forage species (UW 2004).
Chemical
Dicamba or glyphosate are considered effective controls (UW 2004).
Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.
Remarks:
Also known as: Cerastium aquaticum Linnaeus, Alsine aquatica (Linnaeus) Britton, Stellaria aquatica (Linnaeus) Scopoli, Malachium aquaticum
The identification of different chickweed species is difficult. Water chickweed belongs to a group of chickweeds that has flowers with 5 styles and 10 stamens. However, water chickweed has larger flowers and leaves than other members of this group (mainly Cerastium spp.). It resembles Stellaria pubera (starry chickweed) somewhat, but the latter has flowers with 3 styles and leaves that are narrower at the base. Both of these species share the common name 'giant chickweed.'
References
(click for full reference list)
Author:
Cao, L., and R. Sturtevant
Contributing Agencies:
Revision Date:
8/15/2019
Citation for this information:
Cao, L., and R. Sturtevant, 2024, Myosoton aquaticum (L.) Moench: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/greatlakes/FactSheet.aspx?Species_ID=2743&Potential=N&Type=0&HUCNumber=DGreatLakes, Revision Date: 8/15/2019, Access Date: 4/25/2024
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.