Marsilea quadrifolia L.

European water-clover

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New England Distribution

Adapted from BONAP data

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North America Distribution

Adapted from BONAP data

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Facts About

The leaves of water shamrock are divided into four segments that give it the appearance of a clover or shamrock. It is the only water shamrock in New England, and it was introduced from Europe into a lake in Connecticut in 1862.

Habitat

Lacustrine (in lakes or ponds), riverine (in rivers or streams), shores of rivers or lakes

Characteristics

Habitat
aquatic
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf divisions
the leaf blade is compound (divided into leaflets)
Plant growth form
the leaves float on the surface of the water
Spore-bearing leaflets
the spore-bearing fronds are dramatically different from the sterile fronds
Sorus shape
there are no sori, or they are concealed in leaf segments or hardened, capsule-like structures derived from a modified leaflet
Leaf stalk scales
there are no scales on the leaf stalk
Leaf stalk hairs
  • the leaf stalk has hairs
  • there are no hairs on the leaf stalk
Leaf blade length
1.4–4.2 cm
Leaf vein tips
the veins go all the way to the edge of the leaf blade
Show All Characteristics
  • Growth form
    Life form
    the plant is aquatic
    Life stage
    the plant is visible as a typical leaf-bearing fern (sporophyte)
    Spore-bearing leaflets
    the spore-bearing fronds are dramatically different from the sterile fronds
  • Leaves
    Features of leaves
    there are no special features on the leaves
    Leaf blade length
    1.4–4.2 cm
    Leaf blade shape
    the leaf blades are roughly triangular
    Leaf blade tip shape
    the tip of the leaf blade is rounded
    Leaf blade width
    At least 1.2 cm
    Leaf divisions
    the leaf blade is compound (divided into leaflets)
    Leaf lifespan
    the leaves drop off in winter
    Leaf stalk hairs
    • the leaf stalk has hairs
    • there are no hairs on the leaf stalk
    Leaf stalk length
    54–165 mm
    Leaf stalk relative length
    the leaf stalk is more than three quarters as long as the blade
    Leaf stalk scale location
    there are no scales on the leaf stalk
    Leaf stalk scales
    there are no scales on the leaf stalk
    Leaf vein branching
    the secondary veins of the leaf blade split and rejoin to form a netlike pattern
    Leaf vein tips
    the veins go all the way to the edge of the leaf blade
    Lobe or leaflet length
    8–27 mm
    Lobe or leaflet pairs
    2
    Lobe or leaflet shape
    the lobe or leaflet is roughly triangular with the stalk in the center of the widest side (broad-triangular)
    Lobe or leaflet width
    8–27 mm
    Plant growth form
    the leaves float on the surface of the water
    final leaf segment margin
    the topmost lobe or leaflet of the leaf blade has a smooth or lobed edge
  • Place
    Habitat
    aquatic
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • in lakes or ponds
    • in rivers or streams
    • shores of rivers or lakes
  • Spores or spore cones
    Sorus features
    there are no special features on the sorus
    Sorus shape
    there are no sori, or they are concealed in leaf segments or hardened, capsule-like structures derived from a modified leaflet
    Sporangia location
    the spores are enclosed in a hardened, capsule-like structure (sporocarp)
    Sporangium type
    the sporangia are opaque without an annulus and usually without a stalk (leptosporangiate)
    Spore forms
    there are two different types of spores present

Wetland Status

Occurs only in wetlands. (Wetland indicator code: OBL)

New England Distribution and Conservation Status

Distribution

Connecticut
present, invasive, prohibited
Maine
present
Massachusetts
present
New Hampshire
absent
Rhode Island
absent
Vermont
absent

Conservation Status

Exact status definitions can vary from state to state. For details, please check with your state.

Massachusetts
unranked (S-rank: SNR)

Native to North America?

No

Family

Marsileaceae

Genus

Marsilea

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Information from Dichotomous Key of Flora Novae Angliae

1.  Marsilea quadrifolia L. E

European water-clover. CT, MA, ME, NH, RI, VT. Shallow, still or slow-moving water, sometimes stranded on mud.