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• Grass-like plants
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• Schoenoplectus subterminalis

Schoenoplectus subterminalis — water annual-bulrush

Facts

Water bulrush has disjunct eastern and western populations in North America. It often forms lawnlike mats underwater in lakes and slow-moving rivers.

Habitat

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

Characteristics

• Flowers

  Anther length

  2–3.5 mm

  Floral bristle color

  the bristles are pale brown to brown

  Floral bristle number

  5-7

  Floral bristle relative length

  the bristles are between one tenth as long as the achene, and equal in length to the achene

  Floral bristles

  the bristles are straight or slightly curved

  Floral scale hairs

  there are no hairs on the floral scales

  Floral scale length

  4–6 mm

  Floral scale shape

  • the floral scales are lanceolate (widest below the middle, and tapering at both ends)
  • the floral scales are ovate (roughly egg-shaped)

  Floral scale translucent

  the floral scales are translucent

  Flower number per cluster

  1

  Inflorescence bract angle

  the bracts are vertical or angled only slightly outwards

  Inflorescence bract number

  there is just one bract on the inflorescence

  Inflorescence bract position (Sparganium)

  NA

  Inflorescence bracts

  there is only one bract, and it looks like a continuation of the stem

  Inflorescence branching

  the inflorescence is on one or more stems with no branches

  Inflorescence crowding

  • NA
  • the inflorescence is crowded together in one tight cluster

  Inflorescence position

  the inflorescence appears to come from the side of the plant because the involucral bract at its base looks like an extension of the main stem

  Inflorescence shape

  the aggregations within the inflorescence are roughly circular (not flattened) in cross-section

  Inflorescence type

  there is one spike or raceme at the tip of the stem

  Perianth composition

  there are bristles attached at the base of the achene

  Stamen number

  3

  Stigma number

  3

  Style division

  the top two thirds of the style is divided

  floral bristle barbs

  the bristles have tiny barbs on them

  plantlets budding at flower bases

  no

• Fruits or seeds

  Achene beak length

  0.3–0.8 mm

  Achene surface texture

  the achene is smooth (it has no detectable texture)

  Achene tubercle relative width

  NA

  Achene tubercle width

  0 mm

  Capsule relative length

  NA

  Fruit cross-section

  the fruit is triangular to terete (circular) in cross-section

  Fruit length

  2.5–3.5 mm

  Fruit type (general)

  the fruit is like a seed, and surrounded by scales

  Fruit type (specific)

  the fruit is an achene (dry, seed-like fruit) without a tubercle (a swelling or projection, usually of a different color or texture)

  Locules in capsule

  NA

  Seed length

  0 mm

  Seed tail relative length

  0 mm

  Seed tails

  NA

  Tubercle height

  0 mm

• Growth form

  Lifespan

  the plant lives more than two years

  Rhizome thickness

  1 mm

  Underground organs

  • the plant has a rhizome (a horizontal underground stem with roots growing from it)
  • the plant has one or more swollen storage organs underground, such as bulbs or tubers

• Leaves

  Auricle length

  0 mm

  Auricle texture

  NA

  Auricles

  there are no auricles on the leaf sheath

  Leaf blade cross-section

  • the leaf blade is elliptic or circular in cross-section
  • the leaf blade is flat or rolled in at the edges

  Leaf blade length

  Up to 50 mm

  Leaf blade width

  0.2–1 mm

  Leaf form

  the leaves are extremely fine, or they are floating leaves, and do not hold their form out of water

  Leaf position on plant

  the attachment points of all the leaves are at or near the base of the plant

  Leaf septa

  the leaf blades do not have transverse septa

  Leaf sheath hairs

  the leaf sheathes are without hairs

  Pedicel length (Typha)

  0 mm

  Stem leaf blade ligules

  the plant has ligules at the leaf blade bases

  Stem leaf blades

  • there are fully-developed leaves with leaf blades on the main stem
  • there are no leaves on the main stem, or there is a small tooth or tiny blade, or a leaf sheath with no blade

  Width of seed-producing inflorescence

  4–7 mm

• Place

  Habitat

  aquatic

  New England state

  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont

  Specific habitat

  • in lakes or ponds
  • in rivers or streams

• Stem, shoot, branch

  Plant height

  20–150 cm

  Stem shape in cross-section

  the stem is round or oval in cross-section

  Stem texture near tip

  the stem feels smooth near the tip

  Stem thickness at midpoint

  0.5–1 mm

Wetland status

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

New England distribution and conservation status

From the dichotomous key of Flora Novae Angliae