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Isotria medeoloides — small whorled pogonia

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Facts

Small whorled pogonia is globally rare, with most of the world's population occuring in Maine and New Hampshire, where it typically grows in young, open-canopy forests, and disappearing from more mature forests. Plant size and reproduction is positively correlated with light levels, and a small test of canopy thinning appears to confirm this, suggesting a potential conservation tool.

Habitat

Anthropogenic (man-made or disturbed habitats), forest edges, forests

New England distribution

Adapted from BONAP data

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North America distribution

Adapted from BONAP data

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Characteristics

Habitat
terrestrial
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont
Leaf arrangement
whorled: there are three or more leaves per node along the stem
Number of leaves on stem
  • five
  • four
  • six or more
  • three
  • two
Form of lower petal
the labellum does not have a pouch-like shape
Lower petal outline
the labellum is lobed but not fringed
Main color of lower petal
  • green to brown
  • white
  • yellow
Nectar spur
there are no nectar spurs on the flower
Inflorescence type
the inflorescence has only one flower or a pair of flowers on it
Lower petal characteristics
the labellum is lobed
Lower petal length
11–16 mm
Sepal length
12–25 mm
Show all characteristics

  • Flowers

    Flower petal color
    green
    Flower symmetry
    there is only one way to evenly divide the flower (the flower is bilaterally symmetrical)
    Flowering date
    • July
    • June
    • May
    Flowers per inflorescence
    1–3
    Form of lower petal
    the labellum does not have a pouch-like shape
    Hairs on inflorescence axis
    NA
    Inflorescence type
    the inflorescence has only one flower or a pair of flowers on it
    Labellum position
    the labellum is in the lower position on the flower
    Length of flower stalk
    10–15 mm
    Length of narrowed base of lower petal
    0 mm
    Length of peduncle
    10–15 mm
    Lobes at base of lower petal
    0 mm
    Lower petal characteristics
    the labellum is lobed
    Lower petal length
    11–16 mm
    Lower petal outline
    the labellum is lobed but not fringed
    Lower petal strongly red-veined
    no
    Main color of lower petal
    • green to brown
    • white
    • yellow
    Nectar spur
    there are no nectar spurs on the flower
    Nectar spur length
    0 mm
    Number of stamens
    1
    Orientation of side petals
    the lateral petals are angled steeply upwards
    Self-pollinating flowers
    there are no cleistogamous flowers on this plant
    Sepal length
    12–25 mm
    Sepals fused only to sepals
    the sepals are separate from one another
    Shape of viscidium
    NA
    Spots on lower petal
    no
    Spur opening membrane
    NA
    Spur opening shape
    NA

  • Fruits or seeds

    Fruit length
    12–28 mm
    Fruit width
    2–10 mm
    Length of peduncle when in fruit
    5–20 mm
    Seed capsule orientation
    the capsule points upwards or is angled outwards

  • Growth form

    Plant green or not
    the plant is chlorophyllous (it has green parts)
    Roots
    the rhizomes do not resemble coral
    Underground organs
    • there are only slender roots on the plant
    • this plant has a rhizome (a horizontal underground stem with roots growing from it)

  • Leaves

    Bract relative length
    NA
    Features of leaves
    the leaf does not have any of the mentioned special features
    Leaf arrangement
    whorled: there are three or more leaves per node along the stem
    Leaf blade edges
    the edges of the leaf blade have no teeth
    Leaf blade length
    17–85 mm
    Leaf blade shape
    • the leaf blade is elliptic (widest near the middle and tapering at both ends)
    • the leaf blade is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
    Leaf blade tip
    • the tip of the leaf blade is acuminate (tapers to a long, thin point)
    • the tip of the leaf blade is acute (sharply pointed)
    Leaf blade width
    8–40 mm
    Leaves during flowering
    there are leaves on the plant when it is flowering
    Number of bracts on stem
    0
    Number of leaves on stem
    • five
    • four
    • six or more
    • three
    • two

  • Place

    Habitat
    terrestrial
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • edges of forests
    • forests
    • man-made or disturbed habitats

Wetland status

Usually occurs in non-wetlands, but occasionally in wetlands. (Wetland indicator code: FACU)

In New England

Distribution

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

Conservation status

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

Connecticut
extremely rare (S-rank: S1), endangered (code: E)
Maine
rare (S-rank: S2), endangered (code: E)
Massachusetts
extremely rare (S-rank: S1), endangered (code: E)
New Hampshire
rare (S-rank: S2), threatened (code: T)
Rhode Island
historical (S-rank: SH), state historical (code: SH)
Vermont
extirpated (S-rank: SX), endangered (code: E)

From Flora Novae Angliae dichotomous key

1.  Isotria medeoloides (Pursh) Raf. NC

small whorled pogonia. Arethusa medeoloides Pursh; Pogonia affinis Austin ex Gray • CT, MA, ME, NH, RI, VT. Deciduous or evergreen-deciduous, often acidic, forests, usually relatively young forests with an open understory, frequently associated with mild topography and growing in the vicinity of small streams. Vegetative plants of Isotria medeoloides superficially resemble Medeola virginiana. The former has glabrous, hollow stems that arise from short rhizomes, while the latter has pubescent, solid stems that arise from a white tuber.

Native to North America?

Yes

Sometimes confused with

Isotria verticillata:
sepals 34–67 mm long, usually green-yellow in the basal portion and red-purple in the apical portion, and labellum 15–25 mm long (vs. I. medeoloides, with sepals 12–25 mm long, usually green-yellow throughout, and labellum 10–15 mm long).

Synonyms

  • Arethusa medeoloides Pursh
  • Pogonia affinis Austin ex Gray

Family

Orchidaceae

Genus

Isotria