Giant-chickweed (Stellaria aquatica) — identification, habitat & look-alikes

Giant chickweed is a sprawling wild plant that looks like an oversized common chickweed, with white petals split so deeply that its five petals look like ten. Native to Europe and Asia, it now grows wild in parts of the United States, mostly in the East and Midwest, on wet ground along streams, ditches, and meadows. It's also called water chickweed.

Appearance

Growth form: A sprawling, often perennial herb about 8–20 in (20–50 cm) tall. Stems lie on the ground at the base and then curve upward, and creeping underground stems let it form patches.
Leaves: Opposite, heart-shaped to egg-shaped leaves up to about 2 in (5 cm) long. Upper leaves are stalkless and hug the stem.
Flowers: White flowers with five deeply split petals, ten stamens, and five slender styles. Flower stalks are noticeably hairy.
Flowering time: In Illinois it blooms from late spring to late summer.
Fruit: An egg-shaped capsule that splits into five parts, each forked at the tip. The tiny seeds are finely bumpy.

Look-alikes

common chickweedStellaria media

Count the styles in the center of the flower: giant chickweed has 5, common chickweed has 3. Giant chickweed also has bigger leaves and flowers. You'll want a hand lens or a close-up photo.

Why they get mixed upBoth have small white flowers with deeply notched petals.

star chickweedStellaria pubera

Star chickweed has 3 styles and leaves that narrow toward the base, while giant chickweed has 5 styles and heart-shaped leaf bases.

Why they get mixed upStar chickweed is also sometimes called giant chickweed.

mouse-ear chickweedsCerastium

Mouse-ear chickweeds also have 5 styles, but their flowers and leaves are smaller than giant chickweed's.

Why they get mixed upThey share the same flower plan of notched white petals with 5 styles.

Where it lives

Typical habitats: stream banks
roadside ditches
wet meadows
pastures and gardens
Range: Introduced from Eurasia and naturalized in the United States, with records mostly in the East and Midwest (for example Illinois, Indiana, Wisconsin, Minnesota, New Jersey, and West Virginia). In Illinois it turns up occasionally in the north and in a few central counties, and it appears to be spreading.
Preferred conditions: Prefers wet to moist, fertile soil in full sun to light shade, though it can handle short dry spells.

Name and classification

About the name: It is also known as Myosoton aquaticum: because of its five styles and five-parted capsule, some botanists place it in its own genus, apart from the other chickweeds.