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• Schoenoplectus purshianus

Schoenoplectus purshianus — weak-stalked annual-bulrush

Facts

Weak-stalked bulrush inhabits pond shores and temporary pools in all New England states. There are two varieties, one of which is common and widespread (Schoenoplectus purshianus var. purshianus), the other (S. purshianus var. williamsii) being known from only a single population in Massachusetts.

Habitat

Shores of rivers or lakes, wetland margins (edges of wetlands)

Characteristics

• Flowers

  Anther length

  0.4–0.6 mm

  Floral bristle color

  the bristles are pale brown to brown

  Floral bristle number

  • 0
  • 5-7

  Floral bristle relative length

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

  Floral bristles

  the bristles are straight or slightly curved

  Floral scale hairs

  the floral scales have hairs on them

  Floral scale length

  2.5–3 mm

  Floral scale nerves

  • 2-5
  • 7 or more

  Floral scale shape

  the floral scales are obovate (roughly egg-shaped, but with the widest part above the middle)

  Floral scale translucent

  the floral scales are opaque

  Inflorescence bract angle

  the bracts are angled outwards near horizontal or reflexed downwards

  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 branched

  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
  • the inflorescence is at the tip of the plant

  Inflorescence shape

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

  Inflorescence type

  • there are two or more flowers, spikes or flower clusters on a branched inflorescence
  • there is one spike or raceme at the tip of the stem

  Perianth composition

  • there are bristles attached at the base of the achene
  • there is no perianth on the plant

  Stamen number

  3

  Stigma number

  • 2
  • 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

  0.1–0.3 mm

  Achene surface texture

  the achene has very obvious pits or depressions on it

  Achene tubercle relative width

  NA

  Achene tubercle width

  0 mm

  Capsule relative length

  NA

  Fruit cross-section

  the fruit is biconvex or elliptic (widest in the middle and tapering to both ends) in cross-section

  Fruit length

  1.75–2 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 only a single year or less

  Rhizome thickness

  1 mm

  Underground organs

  the plant has a rhizome (a horizontal underground stem with roots growing from it)

• Leaves

  Auricle length

  0 mm

  Auricle texture

  NA

  Auricles

  there are no auricles on the leaf sheath

  Leaf blade cross-section

  • NA
  • the leaf blade is flat or rolled in at the edges

  Leaf blade width

  0.5–1 mm

  Leaf form

  all the leaves 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 no leaves on the main stem, or there is a small tooth or tiny blade, or a leaf sheath with no blade

• Place

  Habitat

  wetlands

  New England state

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

  Specific habitat

  • edges of wetlands
  • shores of rivers or lakes

• Stem, shoot, branch

  Plant height

  10–100 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