clover fern (Invasive Plants of Maryland)

clover fern

Marsilea quadrifolia

Summary ⁶

Marsilea quadrifolia is a herbaceous plant found naturally in central and southern Europe, Caucasia, western Siberia, Afghanistan, south-west India, China, Japan, and Vietnam, though it is considered a weed in some parts of the United States, where it has been well established in the northeast for over 100 years. Its common names include four leaf clover; European waterclover (USA); sushni (India); aalaik keerai (Tamil).

Description ⁷

This perennial herbaceous fern produces basal leaves that are quadrifoliate (divided into 4 leaflets). These leaves are located at the apices of slender petioles about 3-10" long. This fern is mostly aquatic; its leaflets are either slightly submerged, floating, or emergent. Less often, this fern is terrestrial on wet ground. The leaflets are 6-25 mm. (¼-1") long and similarly across; they are obdeltate or obovate in shape with straight lateral margins and convex outer margins. Both the upper and lower surfaces of the leaflets are pale green or pale bluish green; the upper leaflet surface is glabrous, while the lower leaflet surface is glabrous to sparsely short-pubescent. Leaf venation is palmate-reticulate. Aerial leaflets may fold together at night, after which they will spread outward during the day in response to light. The petioles are stramineus (straw-colored) to light green, terete (circular in cross-section), and usually glabrous (less often sparsely short-pubescent). The submerged petioles often curve upward toward the water surface, while emerged petioles have a tendency to lean or sprawl. Near the bases of petioles, there are sporocarps (spore-bearing bodies) on short peduncles up to 12 mm. (½") long. These sporocarps are typically arranged on branched peduncles in groups of 2-3, although there can be only a single sporocarp to as many as 5 sporocarps per peduncle. The bases of these peduncles are attached 1-20 mm. above the bases of petioles. Individual sporocarps are about 3.5-5.0 mm. long, 3.0-3.5 mm. across, and 2.0-2.5 mm. thick; they are ovoid and somewhat flattened in shape with rounded ends and slightly convex sides. The sporocarps are reddish brown, dark brown, or dark purple; young sporocarps are yellow-hairy, while older sporocarps are glabrous. The interior of each sporocarp is divided into several chambers (or sori); these chambers contain both macrospores and microspores that are self-compatible. The root system consists of long slender rhizomes that produce basal leaves at their nodes; the internodes of these rhizomes (distance between adjacent nodes) are up to 4" long. Fine fibrous roots are produced primarily at the nodes and, to a lesser extent, along the internodes.

Habitat and ecology ⁸

Habitat and Ecology

It grows in still waters such as ponds, rice fields and ditches.

Systems

Freshwater

It is considered invasive by the MD Aquatic Nuisance Species Task Force

Sources and Credits

(c) 素珍徐, some rights reserved (CC BY-NC-ND), http://www.flickr.com/photos/11679764@N03/2676867543
(c) anonymous, some rights reserved (CC BY-NC), http://www.biopix.com/PhotosMedium/JCS%20Marsilea%20quadrifolia%2046762.JPG
(c) anonymous, some rights reserved (CC BY-NC), http://www.biopix.com/PhotosMedium/JCS%20Marsilea%20quadrifolia%2046761.JPG
(c) anonymous, some rights reserved (CC BY-NC), http://www.biopix.com/PhotosMedium/JCS%20Marsilea%20quadrifolia%2046760.JPG
(c) anonymous, some rights reserved (CC BY-NC), http://www.biopix.com/PhotosMedium/JCS%20Marsilea%20quadrifolia%2046758.JPG
Adapted by Kate Wagner from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Marsilea_quadrifolia
Adapted by Kate Wagner from a work by (c) John Hilty, some rights reserved (CC BY-NC), http://eol.org/data_objects/29449080
(c) International Union for Conservation of Nature and Natural Resources, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/34562209

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clover fern

Summary 6

Description 7

Habitat and ecology 8