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Cypripedium arietinum — ram's-head lady's-slipper

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Facts

The small but dramatic ram's-head lady's-slipper is rare and protected throughout New England. It flowers early, in mid May to early June, and flowers last only a week or so. Most individuals in a population do not flower in a given year.

Habitat

Forests, swamps

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
  • wetlands
New England state
  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Vermont
Leaf arrangement
alternate: there is one leaf per node along the stem
Number of leaves on stem
  • five
  • four
  • three
Form of lower petal
the labellum has a pouch-like shape
Lower petal outline
the labellum is simple in form
Main color of lower petal
  • green to brown
  • white
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 in the shape of a pouch
Lower petal length
10–16 mm
Sepal length
15–25 mm
Show all characteristics

  • Flowers

    Flower petal color
    • brown
    • green
    • red
    Flower symmetry
    there is only one way to evenly divide the flower (the flower is bilaterally symmetrical)
    Flowering date
    • June
    • May
    Flowers per inflorescence
    1–2
    Form of lower petal
    the labellum has a pouch-like shape
    Hairs on inflorescence axis
    • NA
    • at least some of the hairs on the main stem of the inflorescence have glands
    • the main stem of the inflorescence has hairs entirely without glands
    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 narrowed base of lower petal
    0 mm
    Lobes at base of lower petal
    0 mm
    Lower petal characteristics
    the labellum is in the shape of a pouch
    Lower petal length
    10–16 mm
    Lower petal outline
    the labellum is simple in form
    Lower petal strongly red-veined
    yes
    Main color of lower petal
    • green to brown
    • white
    Nectar spur
    there are no nectar spurs on the flower
    Nectar spur length
    0 mm
    Number of stamens
    2
    Orientation of side petals
    • the lateral petals slant outward
    • the lateral petals slant somewhat downward
    Pollen sacs
    NA
    Self-pollinating flowers
    there are no cleistogamous flowers on this plant
    Sepal length
    15–25 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

    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
    • the bract is longer than the associated flower
    • the bract is shorter than the associated flower
    Features of leaves
    • the leaf does not have any of the mentioned special features
    • the leaf is pleated or folded back and forth along its length
    Leaf arrangement
    alternate: there is one leaf per node along the stem
    Leaf blade edges
    the edges of the leaf blade have no teeth
    Leaf blade length
    50–110 mm
    Leaf blade length to width ratio
    3.1–3.8
    Leaf blade shape
    • the leaf blade is elliptic (widest near the middle and tapering at both ends)
    • the leaf blade is lanceolate (lance-shaped; widest below the middle and tapering at both ends)
    • the leaf blade is oblong (rectangular but with rounded ends)
    • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
    Leaf blade tip
    • the tip of the leaf blade is acute (sharply pointed)
    • the tip of the leaf blade is obtuse (bluntly pointed)
    Leaf blade width
    13–35 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
    • three

  • Place

    Habitat
    • terrestrial
    • wetlands
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Vermont
    Specific habitat
    • forests
    • swamps

Wetland status

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

In New England

Distribution

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

Conservation status

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

Connecticut
historical (S-rank: SH), special concern, extirpated (code: SC*)
Maine
extremely rare (S-rank: S1), endangered (code: E)
Massachusetts
extremely rare (S-rank: S1), endangered (code: E)
New Hampshire
extremely rare (S-rank: S1), endangered (code: E)
Vermont
rare (S-rank: S2), threatened (code: T)

From Flora Novae Angliae dichotomous key

2.  Cypripedium arietinum Ait. f. NC

ram’s-head lady’s-slipper. CT, MA, ME, NH, VT. Deciduous and mixed evergreen-deciduous forests, often on enriched soils due to bedrock influence or colluvial deposits, also in swamps dominated by Thuja occidentalis.

Native to North America?

Yes

Sometimes confused with

Calypso bulbosa:
labellum with a pair of yellow, apical horns and also with evident, yellow bristles, and plants with single basal leaf (vs. C. arietinum, with the labellum lacking a pair of apical horns and also without evident yellow bristles, and plants with 3 or 4 leaves borne on a stem).
Cypripedium acaule:
plants with a pair of basal leaves, the stems scapose, and labellum without a downward projected point, with a cleft-like opening along its entire upper side (vs. C. arietinum, the plants with 3 or 4 stem leaves, the stems leafy, and labellum with a downward projected point and with an +/- circular opening on the upper side).

Family

Orchidaceae

Genus

Cypripedium