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

Caulophyllum thalictroides — blue cohosh

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Facts

Blue cohosh is an attractive wildflower, with an unusual display of the spherical blue fruits held stiffly above the leaf canopy. The roots were widely used my Native Americans as an herbal medicine to treat a range of ailments and as a general tonic.

Habitat

Floodplain (river or stream floodplains), forests

New England distribution

Adapted from BONAP data

Found this plant? Take a photo and post a sighting.

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
Flower petal color
  • blue to purple
  • green to brown
  • yellow
Leaf type
the leaves are compound (made up of two or more discrete leaflets
Leaf arrangement
alternate: there is one leaf per node along the stem
Leaf blade edges
  • the edge of the leaf blade has lobes, or it has both teeth and lobes
  • the edge of the leaf blade is entire (has no teeth or lobes)
Flower symmetry
there are two or more ways to evenly divide the flower (the flower is radially symmetrical)
Number of sepals, petals or tepals
there are six petals, sepals, or tepals in the flower
Fusion of sepals and petals
both the petals and sepals are separate and not fused
Stamen number
6
Fruit type (general)
  • NA
  • the fruit is dry but does not split open when ripe
Fruit length
0 mm
Show all characteristics
  • Clonal plantlets

    Bulbils
    the plant does not appear to have bulbils
    Bulblets replace flowers
    there are no bulblets where the flowers are located
  • Flowers

    Anther attachment
    the anther is attached by its base to the filament
    Anther color
    the anthers show no hint of a pink, reddish or purplish tint
    Anther length
    1 mm
    Anther opening
    the anthers have flaps on them that cover the opening
    Anther spurs
    the anthers do not have spurs on them
    Anther tube length
    0 mm
    Calyx growth after flowering
    the calyx does not grow to cover or partially cover the fruit
    Calyx symmetry
    there are two or more ways to evenly divide the calyx (the calyx is radially symmetrical)
    Carpel hairs
    the carpels have no hairs
    Carpels fused
    the carpel is solitary or (if 2 or more) the carpels are not fused to one another
    Cilia on petals
    the petal margins do not have cilia
    Cleistogamous flowers
    there are no cleistogamous flowers on the plan
    Corolla morphology
    NA
    Corolla palate
    no
    Corona lobe length
    0 mm
    Epicalyx
    the flower does not have an epicalyx
    Epicalyx number of parts
    0
    Filament length
    0.5–1.5 mm
    Filament surface
    the filament is smooth, with no hairs or scales
    Flower appearance
    • the flowers appear at the same time as the leaves
    • the flowers appear before the leaves
    Flower description
    the flower has a superior ovary, and lacks a hypanthium
    Flower length
    6–20 mm
    Flower number
    5–70
    Flower orientation
    the flower points upwards or is angled outwards
    Flower petal color
    • blue to purple
    • green to brown
    • yellow
    Flower reproductive parts
    the flower has both pollen- and seed-producing parts
    Flower symmetry
    there are two or more ways to evenly divide the flower (the flower is radially symmetrical)
    Flowers sunken into stem
    no
    Form of style
    the style is narrow at the tip and unbranched
    Fringed petal edges
    the petals are not fringed
    Fused stamen clusters
    NA
    Fusion of sepals and petals
    both the petals and sepals are separate and not fused
    Hairs on flower stalk
    the flower stalk has no hairs on it
    Hairs on inflorescence
    the axis of the inflorescence has no hairs on it
    Horns in hoods (Asclepias)
    NA
    Hypanthium
    the flower does not have a hypanthium
    Hypanthium length
    0 mm
    Inflorescence length
    30–60 mm
    Inflorescence one-sided
    the flowers are arrayed in a spiral around the inflorescence axis or branches, or occur singly, or in several ranks
    Inner tepals (Rumex)
    NA
    Length of peduncle
    At least 30 mm
    Marks on petals
    there are no noticeable marks on the petals
    Nectar spur
    the flower has no nectar spurs
    Number of branches in umbel
    0
    Number of carpels
    1
    Number of pistils
    1
    Number of sepals, petals or tepals
    there are six petals, sepals, or tepals in the flower
    Number of styles
    1
    Ovary position
    the ovary is above the point of petal and/or sepal attachment
    Perianth shape
    the perianth is rotate (platter-shaped, the corolla flattened, circular, with nearly horizontally spreading lobes)
    Petal and sepal arrangement
    the flower includes two cycles of petal- or sepal-like structures
    Petal and sepal colors
    • blue to purple
    • green to brown
    • yellow
    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 folding in bud
    the petals in bud are arranged in a cycle with edges overlapping like roof shingles (imbricate)
    Petal folds or pleats
    the petals of the flower do not have folds or plaits
    Petal glandular dots or scales
    no
    Petal hairs (Viola)
    NA
    Petal hairs on inner/upper surface
    there are no hairs on the inner/upper petal surface
    Petal length
    1–2.5 mm
    Petal length relative to sepals
    the petals are shorter than the sepals
    Petal nectaries
    the petals have at least one nectary
    Petal number
    6
    Petal shape
    the petal outline is another shape
    Petal tip shape
    the petal tip is rounded
    Petal tips (Cuscuta)
    NA
    Petal width
    2 mm
    Raceme attachment (Veronica)
    NA
    Reproductive system
    all the flowers have both carpels and stamens (synoecious)
    Scales inside corolla
    no
    Sepal and petal color
    the sepals are different from the petals
    Sepal appearance
    • the sepals are green or brown, and leaf-like in texture
    • the sepals resemble petals in color and texture
    Sepal appendages
    the sepals do not have appendages on them
    Sepal appendages (Oenothera)
    NA
    Sepal auricles
    the sepals have no auricles
    Sepal cilia
    the sepals do not have cilia
    Sepal color
    • blue to purple
    • green to brown
    • yellow
    Sepal features
    the sepals do not have any of the mentioned special features
    Sepal length
    3–6 mm
    Sepal number
    6
    Sepal orientation
    the sepals are slightly curved outwards from the corolla
    Sepal relative length
    NA
    Sepal shape
    • the sepal outline is oblong (rectangular, but with rounded ends)
    • the sepal outline is ovate (widest below the middle and broadly tapering at both ends)
    • the sepal outline is spatulate (roughly spoon-shaped; narrow near the base, suddenly widening to a rounded tip)
    Sepal texture
    the sepals are either very thin but flexible, like a membrane, or they are leaf-like in texture
    Sepal tip shape
    the sepal tip is rounded
    Sepal uniformity
    all the sepals are about the same size
    Sepals fused only to sepals
    the sepals are separate from one another
    Spur length
    0 mm
    Spur number
    NA
    Stamen appendages
    stamen appendages are absent
    Stamen attachment
    the stamens are not attached to the petals or tepals
    Stamen lengths differ
    the stamens are all approximately the same length
    Stamen morphology
    the stamens within each cycle are the same
    Stamen number
    6
    Stamen position relative to petals
    the stamens are lined up with the petals
    Stamen relative length
    anything
    Stamens fused
    the stamens are not attached to one another
    Staminodes
    there are no staminodes on the flower
    Stigma position
    the stigmas are positioned at the tip of the style
    Style length
    0.25–1 mm
    Style petal-like
    the styles are not petal-like
    Style relative length
    NA
    Surface of ovary
    the ovary surface has no points, bumps or wrinkles
    Umbel flower reproductive parts
    NA
    Upper lip of bilabiate corolla
    NA
  • Fruits or seeds

    Achene relative orientation
    NA
    Achene shape
    NA
    Achene surface (Polygonum)
    NA
    Achene type
    NA
    Berry color
    NA
    Capsule color (Viola)
    NA
    Capsule ribs
    NA
    Capsule splitting
    NA
    Carpel beak length
    0 mm
    Fruit (pyxis) dehiscence
    NA
    Fruit beak length
    0 mm
    Fruit cross-section
    • NA
    • the fruit is round in cross-section
    Fruit features (Brassicaceae)
    NA
    Fruit length
    0 mm
    Fruit length relative to sepals
    NA
    Fruit length to width ratio
    0
    Fruit locules
    NA
    Fruit shape
    NA
    Fruit stalk orientation
    the fruits point upward or spread or curve outward
    Fruit type (general)
    • NA
    • the fruit is dry but does not split open when ripe
    Fruit type (specific)
    NA
    Fruit width
    0 mm
    Hair type on fruit
    NA
    Hairs on fruit
    NA
    Legumes (Fabaceae)
    NA
    Mericarp length
    0 mm
    Mericarp segment shape (Desmodium)
    NA
    Other markings on berry
    NA
    Ovary stipe
    the ovary or fruit does not have a stipe
    Placenta arrangement
    the plant has basal placentation, where one or a few ovules develop at the base of a simple or compound ovary
    Relative fruit length
    0
    Rows of seeds in fruit (Brassicaceae)
    NA
    Schizocarpic fruit compression
    NA
    Schizocarpic fruit segments
    0
    Seed length
    5–8 mm
    Seed number
    2
    Seed relative length
    the seed is about as long as it is wide
    Seed surface
    • the seed is hairless
    • the seed is smooth or without clear markings
    Seeds comose
    no hairs
    Septum in fruit (Brassicaceae)
    NA
    Wings on fruit
    • NA
    • the fruit does not have wings on it
    prickles on fruits
    • NA
    • the fruits do not have thorn-like defensive structures
  • Glands or sap

    Glands on leaf blade
    the leaf blades do not have glandular dots or scales
    Sap
    the sap is clear and watery
    Sap color
    the sap is clear
  • Growth form

    Growth form
    the plant is an herb (it has self-supporting stems)
    Horizontal rooting stem
    the plant does not have stolons
    Lifespan
    the plant lives more than two years
    Parasitism
    the plant is not parasitic
    Plant color
    the leaves or young stems of the plant are green
    Plants darken when dry
    no
    Spines on plant
    the plant has no spines
    Underground organs
    the plant has a rhizome (a horizontal underground stem with roots growing from it)
  • Leaves

    Bracteole edges
    the bracteole margins are entire (without teeth, lobes or hairs)
    Bracteole length
    1–3 mm
    Bracteole number (Apiaceae)
    0
    Bracteoles
    the plant has bracteoles between the primary bracts and the flowers
    Bracts in plantain (Plantago)
    NA
    Final leaf segment length (compound lvs only)
    30–80 mm
    Final leaf segment length to width ratio (compound lvs only)
    0.8–1.5
    Final leaf segment width (compound lvs only)
    20–100 mm
    Floral bract texture
    NA
    Floral bracts
    the flower does not have bracts
    Flower bract length
    0 mm
    Hairs on leaf stalk
    the petiole has no hairs on it
    Hairs on underside of leaf
    the underside of the leaf is not hairy, or it has very few hairs
    Hairs on upper side of leaf
    the upper side of the leaf is not hairy, or it has very few hairs
    Hooked hairs on underside of leaf
    no
    Inflated hairs on leaf
    the leaf blade does not have inflated hairs on it
    Leaf arrangement
    alternate: there is one leaf per node along the stem
    Leaf blade base
    • the leaf has a distinct leaf stalk (petiole)
    • 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
    • the base of the leaf blade is rounded
    Leaf blade base symmetry
    the leaf blade base is symmetrical
    Leaf blade bloom
    • the underside of the leaf has no noticeable bloom
    • there is a noticeable powdery or waxy bloom on the underside of the leaf
    Leaf blade edges
    • the edge of the leaf blade has lobes, or it has both teeth and lobes
    • the edge of the leaf blade is entire (has no teeth or lobes)
    Leaf blade flatness
    the leaf is flat (planar) at the edges
    Leaf blade hairs
    NA
    Leaf blade primary vein pattern
    the secondary veins branch off at intervals from the primary vein
    Leaf blade shape
    the leaf blade is obovate (egg-shaped, but with the widest point above the middle of the leaf blade)
    Leaf blade surface colors
    the upper side of the leaf blade is relatively uniform in color
    Leaf blade texture
    the leaf blade is herbaceous (has a leafy texture)
    Leaf blade vein pattern
    the major veins of the leaf blade branch, but do not rejoin
    Leaf blade veins
    the leaf blade has one main vein running from the base towards the tip (it may or may not have secondary veins)
    Leaf duration
    the leaves drop off in winter (or they whither but persist on the plant)
    Leaf form
    the leaves are green, with an expanded blade and a leaf-like texture
    Leaf hair orientation
    NA
    Leaf sheath length
    0 mm
    Leaf shiny
    the upper side of the leaf is dull or slightly shiny
    Leaf spines
    there are no spines on the leaf edges
    Leaf stalk
    • the leaves have leaf stalks
    • the leaves have no leaf stalks, but attach directly to the stem
    Leaf stalk attachment to leaf
    the petiole attaches at the basal margin of the leaf blade
    Leaf stalk base
    the petiole base is narrow where it attaches to the stem
    Leaf teeth and lobes
    • the edge of the leaf blade is entire (has no teeth or lobes)
    • the leaf has a row of two or more lobes on each side of the central axis
    Leaf tip
    the tip of the leaf blade is acute (sharply pointed)
    Leaf tufts in axils
    there are no clusters of smaller leaves growing out of axils
    Leaf type
    the leaves are compound (made up of two or more discrete leaflets
    Leaf types
    • NA
    • There is a gradual change in appearance of the leaves from the base (or near the base) of the plant to those from further up on the stem, with leaves progressively changing as one moves higher on the stem (often becoming shorter, or less toothed/lobed, and/or with shorter petioles).
    Leaf variation
    the leaves are nearly similar in size, prominence of teeth, and length of stalks throughout the stem
    Leaflet number
    At least 3
    Leaflet petiolules
    the leaflets of the compound leaf have petiolules
    Leaves per node
    there is one leaf per node along the stem
    Pinnately compound leaf type
    the pinnately compound leaves have a terminal leaflet (and usually have an odd number of leaflets per axis)
    Specific leaf type
    • the leaf has a row of two or more lobes on each side of the central axis, and each lobe itself has rows of lobes on each side of the lobe's central axis
    • the leaf has lobes that themselves have lobes, and these secondary lobes also have lobes; there may be more than three levels of lobes
    Stipels
    there are no stipels at the bases of the petiolules
    Stipule edges
    NA
    Stipule features
    NA
    Stipule fused to leaf stalk
    NA
    Stipule length
    0 mm
    Stipule shape
    NA
    Stipules
    there are no stipules on the plant
    Teeth per side of leaf blade
    0
  • Place

    Habitat
    terrestrial
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • forests
    • river or stream floodplains
  • Stem, shoot, branch

    Branched tendrils
    NA
    Direction of stem hairs
    NA
    Flowering stem cross-section
    the flowering stem is circular, or with lots of small angles so that it is roughly circular
    Hair between stem nodes
    the stem has no hairs between the nodes
    Hairs between stem nodes
    the stem has no hairs between the nodes
    Hooked hairs on stem between nodes
    no
    Leaves on stem
    there is at least one full leaf above the base of the flowering stem
    Length of hairs between stem nodes
    0 mm
    Plant height
    20–90 cm
    Stem bloom
    • the stem has a powdery or waxy film on it that can be rubbed away
    • there is no powdery or waxy film on the stem
    Stem hair distribution
    NA
    Stem nodes swollen
    the stem is not swollen at the nodes
    Stem orientation
    the stems are upright or angled outwards
    Stem roughness between nodes
    the stem does not feel rough
    Stem spacing
    the plant is solitary, or a few plants are growing together
    Stem succulence
    the stems are not succulent
    Tendril origin
    NA
    Tendrils
    the plant does not have tendrils
    Wings on stem
    the stem does not have wings on it

Wetland status

Not classified

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.

Maine
unranked (S-rank: SNR)
Massachusetts
fairly widespread (S-rank: S4)
Rhode Island
extremely rare (S-rank: S1), state threatened (code: ST)

From Flora Novae Angliae dichotomous key

2.  Caulophyllum thalictroides (L.) Michx. N

blue cohosh. CT, MA, ME, NH, RI, VT. Mesic, deciduous forests, often rich and rocky, high-terrace flood plain forests.

Native to North America?

Yes

Sometimes confused with

Caulophyllum giganteum:
flowers appearing before expansion of the leaves, mostly numbering 4-18 per inflorescence, and with purple to purple-brown sepals 6-9 mm long (vs. C. thalictroides, with flowers appearing with the leaves, mostly numbering 5-70 per inflorescence, and with usually yellow to yellow-green sepals 3-6 mm long).

Family

Berberidaceae

Genus

Caulophyllum