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

Asclepias verticillata — whorled milkweed

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Facts

Whorled milkweed is distinguished by its whorles of very narrow leaves. New England is at the northeastern limit of its range, and the species is quite rare in some states.

Habitat

Cliffs, balds, or ledges, ridges or ledges, woodlands

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
  • Massachusetts
  • Rhode Island
  • Vermont
Flower petal color
  • green to brown
  • white
Leaf type
the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
Leaf arrangement
opposite: there are two leaves per node along the stem
Leaf blade edges
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 five petals, sepals, or tepals in the flower
Fusion of sepals and petals
the petals or the sepals are fused into a cup or tube
Stamen number
5
Fruit type (general)
the fruit is dry and splits open when ripe
Fruit length
70–100 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 opening
    the anthers have some other type of opening
    Anther spurs
    the anthers do not have spurs on them
    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 carpels are 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
    Epicalyx
    the flower does not have an epicalyx
    Epicalyx number of parts
    0
    Filament surface
    the filament is smooth, with no hairs or scales
    Flower appearance
    the flowers appear after the leaves have appeared
    Flower description
    the flower has a superior ovary, and lacks a hypanthium
    Flower orientation
    the flower points upwards or is angled outwards
    Flower petal color
    • green to brown
    • white
    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 flower has two or more completely separate styles
    Fringed petal edges
    the petals are not fringed
    Fusion of sepals and petals
    the petals or the sepals are fused into a cup or tube
    Horns in hoods (Asclepias)
    the corona horns project out of the corona hoods
    Hypanthium
    the flower does not have a hypanthium
    Inflorescence one-sided
    the flowers are arrayed in a spiral around the inflorescence axis or branches, or occur singly, or in several ranks
    Inflorescence type
    the inflorescence is a simple umbel (with an axis so short it appears the flowers all originate from the same point)
    Inner tepals (Rumex)
    NA
    Marks on petals
    there are no noticeable marks on the petals
    Nectar spur
    the flower has no nectar spurs
    Number of pistils
    2
    Number of sepals, petals or tepals
    there are five petals, sepals, or tepals in the flower
    Number of styles
    2
    Ovary position
    the ovary is above the point of petal and/or sepal attachment
    Petal and sepal arrangement
    the flower includes three distinct cycles of petal- or sepal-like structures
    Petal and sepal colors
    • green to brown
    • white
    Petal appearance
    the petals are thin and delicate, and pigmented (colored other than green or brown)
    Petal base
    the petal narrows gradually or does not narrow at the base
    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 relative to sepals
    the petals are longer than the sepals
    Petal nectaries
    the petals do not have nectaries
    Petal number
    5
    Petal shape
    the petal outline is elliptic (shaped like an ellipse; widest near the middle and tapering at both ends)
    Petal tip shape
    the petal tip is acute (sharply pointed)
    Petal tips (Cuscuta)
    NA
    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
    Sepal appendages
    the sepals do not have appendages on them
    Sepal appendages (Oenothera)
    NA
    Sepal auricles
    the sepals have no auricles
    Sepal color
    green to brown
    Sepal features
    the sepals do not have any of the mentioned special features
    Sepal number
    5
    Sepal orientation
    the sepals are curved outwards and downwards from the corolla
    Sepal uniformity
    all the sepals are about the same size
    Spur number
    NA
    Stamen attachment
    • the stamens are attached at or near the bases of the petals or tepals
    • the stamens are attached at or near the bases of the petals or tepals
    Stamen morphology
    the stamens within each cycle are the same
    Stamen number
    5
    Stamen position relative to petals
    the stamens are lined up with the petals
    Staminodes
    there are no staminodes on the flower
    Stigma position
    the stigmas are in another position
    Style petal-like
    the styles are not petal-like
    Style relative length
    the stigma protrudes beyond the mouth of the corolla
    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
    Fruit (pyxis) dehiscence
    NA
    Fruit beak length
    0 mm
    Fruit cross-section
    the fruit is round in cross-section
    Fruit features (Brassicaceae)
    NA
    Fruit length
    70–100 mm
    Fruit length relative to sepals
    NA
    Fruit locules
    one
    Fruit shape
    • the fruit is another shape than those described
    • the fruit is ellipsoid (widest in the middle and tapering to each end)
    Fruit stalk orientation
    the fruits point upward or spread or curve outward
    Fruit type (general)
    the fruit is dry and splits open when ripe
    Fruit type (specific)
    the fruit is a follicle (has one ovary that splits along one side to release the seeds)
    Hair type on fruit
    NA
    Hairs on fruit
    the fruits are not hairy
    Legumes (Fabaceae)
    NA
    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 parietal placentation, where ovules develop on the wall or slight outgrowths of the wall forming broken partitions within a compound ovary
    Rows of seeds in fruit (Brassicaceae)
    NA
    Schizocarpic fruit compression
    NA
    Schizocarpic fruit segments
    0
    Seed relative length
    the seed is longer than it is wide
    Seeds comose
    hairs are present
    Septum in fruit (Brassicaceae)
    NA
    Wings on fruit
    the fruit does not have wings on it
    prickles on fruits
    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 milky and opaque, and may be white or colored
    Sap color
    the sap is white

  • 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

  • Leaves

    Bracteole edges
    NA
    Bracteole number (Apiaceae)
    0
    Bracteole shape
    NA
    Bracteoles
    there are no bracteoles on the plant
    Bracts in plantain (Plantago)
    NA
    Final leaf segment length (compound lvs only)
    0 mm
    Final leaf segment length to width ratio (compound lvs only)
    0
    Hairs on underside of leaf
    • the underside of the leaf is fuzzy or hairy
    • 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
    opposite: there are two leaves 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
    Leaf blade base symmetry
    the leaf blade base is symmetrical
    Leaf blade edges
    the edge of the leaf blade is entire (has no teeth or lobes)
    Leaf blade flatness
    • the edges of the leaf are curled under
    • the leaf is flat (planar) at the edges
    Leaf blade hairs
    NA
    Leaf blade length
    20–50 mm
    Leaf blade primary vein pattern
    the secondary veins branch off at intervals from the primary vein
    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 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 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 no leaf stalks, but attach directly to the stem
    Leaf stalk attachment to leaf
    • NA
    • the petiole attaches at the basal margin of the leaf blade
    Leaf stalk base
    • NA
    • 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)
    Leaf 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 tufts in axils
    • there are clusters of smaller leaves growing out of axils
    • there are no clusters of smaller leaves growing out of axils
    Leaf type
    the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
    Leaf types
    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
    0
    Leaflet petiolules
    NA
    Leaves per node
    there are two leaves per node along the stem
    Pinnately compound leaf type
    NA
    Specific leaf type
    the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
    Stipels
    NA
    Stipule edges
    NA
    Stipule features
    NA
    Stipule fused to leaf stalk
    NA
    Stipule shape
    NA
    Stipules
    there are no stipules on the plant

  • Place

    Habitat
    terrestrial
    New England state
    • Connecticut
    • Massachusetts
    • Rhode Island
    • Vermont
    Specific habitat
    • cliffs, balds, or ledges
    • ridges or ledges
    • woodlands

  • Stem, shoot, branch

    Branched tendrils
    NA
    Flowering stem cross-section
    • the flowering stem is circular, or with lots of small angles so that it is roughly circular
    • the flowering stem is roughly square
    Hair between stem nodes
    • the stem has hairs between the nodes
    • the stem has no hairs between the nodes
    Hairs between stem nodes
    • the hairs on the stem are plain, without glands or branches, and not tangled
    • 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
    Plant height
    20–50 cm
    Stem hair distribution
    • NA
    • the hairs on the stem are arranged in lines running down the stem from the edges of the leaf bases
    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

Occurs only in non-wetlands. (Wetland indicator code: UPL)

In New England

Distribution

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

Conservation status

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

Massachusetts
rare (S-rank: S2), threatened (code: T)
Rhode Island
extremely rare (S-rank: S1), concern (code: C)
Vermont
extremely rare (S-rank: S1), endangered (code: E)

From Flora Novae Angliae dichotomous key

9.  Asclepias verticillata L. N

whorled milkweed. CT, MA, RI, VT. Rocky woodlands, open glades, balds, cliff bases.

Native to North America?

Yes

Family

Apocynaceae

Genus

Asclepias