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Native Plant Trust: Go Botany Discover thousands of New England plants

Iris prismatica — slender blue iris

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Facts

Slender blue iris is so named because of its very narrow leaf blades. It is native to salt, brackish and fresh marshes, meadows and shorelines along the Atlantic coast from Georgia to Maine.

Habitat

Brackish or salt marshes and flats, fresh tidal marshes or flats, marshes, meadows and fields, shores of rivers or lakes

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
Leaf arrangement
  • alternate: there is one leaf per node along the stem
  • basal: the leaves are growing only at the base of the plant
Leaf blade shape
the leaf blade is linear (very narrow with more or less parallel sides)
Leaf blade length
300–700 mm
Flower petal color
  • blue to purple
  • white
Flower petal length
35–45 mm
Petal fusion
the perianth parts are fused to form a tube, cup, or bell shape
Inflorescence type
  • the inflorescence is a scorpioid cyme (a curled cyme that uncurls as the flowers sequentially bloom)
  • the inflorescence is an umbel (with an axis so short it appears the flowers all originate from the same point)
Ovary position
the ovary is below the point of petal and/or sepal attachment
Fruit type (specific)
the fruit is a capsule (splits along two or more seams, apical teeth or pores when dry, to release two or more seeds)
Fruit length
30–40 mm
Show all characteristics

  • Clonal plantlets

    Axillary bulblets
    there are no bulblets being produced in axils

  • Flowers

    Anther attachment
    the anther is attached by its base to the filament
    Bulblets replace flowers
    there are no bulblets where the flowers are located
    Carpels fused
    the carpels are fused (the number of carpels equals the number of locules)
    Flower bracts
    there are bracts associated with the flower
    Flower number
    3–7
    Flower orientation
    the flowers point upward or spread or curve outward
    Flower petal color
    • blue to purple
    • white
    Flower petal length
    35–45 mm
    Flower shape
    the flower is another shape
    Flower symmetry
    there are two or more ways to evenly divide the flower (the flower is radially symmetrical)
    Form of style
    the style is branched above the base
    Fringed petal edges
    the petals are not fringed
    Inflorescence type
    • the inflorescence is a scorpioid cyme (a curled cyme that uncurls as the flowers sequentially bloom)
    • the inflorescence is an umbel (with an axis so short it appears the flowers all originate from the same point)
    Length of flower stalk
    30–70 mm
    Length of peduncle
    300–800 mm
    Marks on petals
    the petals have spots or streaks on them
    Nectar spur
    the flower has no nectar spurs
    Number of carpels
    3
    Number of pistils
    1
    Number of sepals and/or petals
    there are six petals, sepals or tepals in the flower
    Number of styles
    1
    Ovary position
    the ovary is below the point of petal and/or sepal attachment
    Petal and sepal arrangement
    the flower includes two cycles of petal- or sepal-like structures
    Petal appearance
    the petals are thin and delicate, and pigmented (colored other than green or brown)
    Petal base
    the petal narrows abruptly at the base
    Petal fusion
    the perianth parts are fused to form a tube, cup, or bell shape
    Sepal appearance
    the sepals resemble petals in color and texture
    Sepal length
    40–50 mm
    Sepal orientation
    • the sepals are curved outwards and downwards
    • the sepals are slightly curved outwards from the plant
    Sepals fused only to sepals
    the sepals are separate from one another
    Spathe
    • the plant does not have a spathe
    • the plant has a spathe surrounding the flower spike
    Spathe form
    NA
    Spathe length
    20–40 mm
    Stamen number
    3
    Stamen position relative to petals
    the stamens are lined up with the sepals
    Stamen types
    the stamens within a cycle are all similar
    Stamens fused
    the stamens are not fused to one another
    Stamens fused outwards
    the stamens are fused to the petals or tepals at or near their bases
    Style length
    30–37 mm
    Style petal-like
    the style is broad and flattened like a petal
    Tepals
    the petals and sepals are similar in size and color

  • Fruits or seeds

    Berry color
    NA
    Capsule ridges
    • there are no ribs or wings on the capsule
    • there are three ribs or wings on the capsule
    Fruit compartments
    there are three locules in the fruit
    Fruit cross-section
    the fruit is roughly triangular in cross-section
    Fruit length
    30–40 mm
    Fruit type (general)
    the fruit is dry and splits open when ripe
    Fruit type (specific)
    the fruit is a capsule (splits along two or more seams, apical teeth or pores when dry, to release two or more seeds)
    Fruit width
    12–14 mm
    Other markings on berry
    NA

  • Glands or sap

    Sap
    the sap is clear and watery

  • Growth form

    Lifespan
    the plant lives more than two years
    Underground organs
    the plant has a rhizome (a horizontal underground stem with roots growing from it)

  • Leaves

    Leaf arrangement
    • alternate: there is one leaf per node along the stem
    • basal: the leaves are growing only at the base of the plant
    Leaf blade basal lobes
    the leaf blades do not have basal lobes
    Leaf blade base
    • the leaf blade clasps the stem at the base, or the leaf blade goes all the way around the stem, so that the stem appears to pierce the leaf blade
    • the leaf has no stalk
    Leaf blade base shape
    the base of the leaf blade is cuneate (wedge-shaped, tapers to the base with relatively straight, converging edges), or narrow
    Leaf blade cross-section
    the leaf blade is more or less flat in cross-section
    Leaf blade faces
    the surfaces of the leaf blade are composed of tissues from the abaxial side only
    Leaf blade form
    Fully-formed (i.e., expanded), +/- green leaf blades are found somewhere on the plant
    Leaf blade length
    300–700 mm
    Leaf blade orientation
    the edge of the leaf blade faces the stem of the plant
    Leaf blade shape
    the leaf blade is linear (very narrow with more or less parallel sides)
    Leaf blade surface colors
    the upper side of the leaf blade is relatively uniform in color
    Leaf blade tip
    the tip of the leaf blade is acute (sharply pointed)
    Leaf blade veins
    the lateral veins are parallel or slightly arched in the direction of the tip
    Leaf blade width
    1–7 mm
    Leaf stalk length
    0 mm
    Leaf type
    the leaves are simple (i.e., lobed or unlobed but not separated into leaflets
    Leaflet number
    0
    Stipule twining
    NA
    Stipules
    there are no stipules on this plant

  • Place

    Habitat
    wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    Specific habitat
    • brackish or salt marshes and flats
    • fresh tidal marshes or flats
    • marshes
    • meadows or fields
    • shores of rivers or lakes

  • Scent

    Plant odor
    the leaves have no particular smell

  • Stem, shoot, branch

    Flowering stem growth form
    the flowering stem is held upright
    Flowering stem interior
    • the flowering stem is hollow
    • the flowering stem is solid
    Flowering stem leaves
    there is at least one fully-formed leaf on the flowering stem

Wetland status

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

In New England

Distribution

Connecticut
present
Maine
present
Massachusetts
present
New Hampshire
present
Rhode Island
present
Vermont
absent

Conservation status

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

Maine
rare (S-rank: S2), threatened (code: T)
Massachusetts
fairly widespread (S-rank: S4)
New Hampshire
extremely rare (S-rank: S1), endangered (code: E)

From Flora Novae Angliae dichotomous key

5.  Iris prismatica Pursh ex Ker-Gawl. N

slender blue iris. CT, MA, ME, NH, RI; also reported from VT by Seymour (1982), but specimens are unknown; mainly in coastal counties. Fresh to saline marshes, meadows, shorelines. This species has narrow leaf blades 1–7 mm wide.

Native to North America?

Yes

Sometimes confused with

Iris versicolor:
adnate floral tube longer than 5 mm tall, branches of rhizome similar to the primary rhizome in size and texture, and capsules rounded-triangular in cross-section (vs. I. prismatica, with the adnate floral tube 2–3 mm tall, branches of rhizomes unlike the primary rhizome, bearing scale-like leaves along its length, expanding at apex to produce green leaves, and capsules sharply triangular in cross-section).

Family

Iridaceae

Genus

Iris