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

Conium maculatum — poison-hemlock

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Facts

Poison-hemlock is so poisonous that only a small amount can kill humans when ingested. Ancient Greeks used this plant to make poison to commit murder or assassination, as in the case of Socrates in 399 B.C.

Habitat

Anthropogenic (man-made or disturbed habitats), forest edges, meadows and fields

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
Flower petal color
white
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 has teeth
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
both the petals and sepals are separate and not fused
Stamen number
5
Fruit type (general)
the fruit is dry but does not split open when ripe
Fruit length
2–4 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 narrow slits or furrows that run lengthwise along the anthers
    Anther spurs
    the anthers do not have spurs on them
    Calyx growth after flowering
    NA
    Carpel hairs
    the carpels have no hairs
    Carpels fused
    the carpels are fused to one another
    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 surface
    the filament is smooth, with no hairs or scales
    Flower description
    the flower has an inferior ovary, with or without a hypanthium
    Flower petal color
    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
    Fused stamen clusters
    NA
    Fusion of sepals and petals
    both the petals and sepals are separate and not fused
    Hairs on inflorescence
    the axis of the inflorescence has hairs entirely without glands
    Horns in hoods (Asclepias)
    NA
    Hypanthium
    the flower does not have a hypanthium
    Inflorescence length
    20–30 mm
    Inflorescence one-sided
    the flowers are arrayed in a spiral around the inflorescence axis or branches, or occur singly, or in several ranks
    Inflorescence width
    40–70 mm
    Inner tepals (Rumex)
    NA
    Interior flower disk
    the flower has an interior disc
    Length of flower stalk
    1–5 mm
    Length of peduncle
    20–70 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
    6–20
    Number of carpels
    2
    Number of pistils
    1
    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 below the point of petal and/or sepal attachment
    Petal and sepal arrangement
    the flower includes only one cycle of petals or sepals
    Petal and sepal colors
    white
    Petal appearance
    the petals are thin and delicate, and pigmented (colored other than green or brown)
    Petal folding in bud
    the petals in bud meet exactly at the margins without overlapping (valvate)
    Petal folds or pleats
    the petals of the flower do not have folds or plaits
    Petal hairs (Viola)
    NA
    Petal length
    1.5 mm
    Petal number
    5
    Petal shape
    the petal outline is another shape
    Petal tip shape
    the petal tip is retuse (with a blunt or rounded apex and a notch at the center)
    Petal tips (Cuscuta)
    NA
    Petal width
    1 mm
    Raceme attachment (Veronica)
    NA
    Reproductive system
    all the flowers have both carpels and stamens (synoecious)
    Scales inside corolla
    no
    Sepal and petal color
    NA
    Sepal appearance
    NA
    Sepal appendages
    the sepals do not have appendages on them
    Sepal appendages (Oenothera)
    NA
    Sepal auricles
    NA
    Sepal cilia
    NA
    Sepal color
    NA
    Sepal features
    the sepals do not have any of the mentioned special features
    Sepal length
    0 mm
    Sepal number
    0
    Sepal orientation
    NA
    Sepal relative length
    NA
    Sepal shape
    NA
    Sepal texture
    NA
    Sepal tip shape
    NA
    Sepal uniformity
    NA
    Sepals fused only to sepals
    NA
    Stamen attachment
    the stamens are not attached to the petals or tepals
    Stamen number
    5
    Stamen position relative to petals
    the stamens are lined up with the sepals
    Stamens fused
    the stamens are not attached to one another
    Staminodes
    there are no staminodes on the flower
    Style petal-like
    the styles are not petal-like
    Surface of ovary
    the ovary surface has no points, bumps or wrinkles
    Umbel flower reproductive parts
    all the flowers at the final division of the umbel have both carpels and stamens
    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 cross-section
    the fruit is at least somewhat flattened
    Fruit features (Brassicaceae)
    NA
    Fruit length
    2–4 mm
    Fruit locules
    two
    Fruit shape
    the fruit is ovoid (egg-shaped)
    Fruit stalk orientation
    the fruits point upward or spread or curve outward
    Fruit type (general)
    the fruit is dry but does not split open when ripe
    Fruit type (specific)
    the fruit is a schizocarp (when dry it splits into sections, each holding one or more seeds)
    Fruit width
    1.5–2.5 mm
    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 axile placentation, in which the ovules are attached where the septa of a compound ovary are united, usually on the central axis, or to the septa themselves
    Rows of seeds in fruit (Brassicaceae)
    NA
    Schizocarpic fruit compression
    the fruit is flattened perpendicular to the commissure
    Schizocarpic fruit segments
    2
    Seed number
    2
    Seed surface
    the seed has a surface characteristic other than those listed
    Septum in fruit (Brassicaceae)
    NA
    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 clear and watery
    Sap color
    the sap is clear

  • Growth form

    Growth form
    the plant is an herb (it has self-supporting stems)
    Lifespan
    • the plant lives for two years
    • the plant lives only a single year or less
    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
    there is a thickened taproot on the plant

  • Leaves

    Bracteole length
    1.5–3 mm
    Bracteole number (Apiaceae)
    3–6
    Bracteole shape
    the bracteoles are ovate (widest below the middle, and broadly tapering to both ends--egg-shaped)
    Bracteoles
    the plant has bracteoles between the primary bracts and the flowers
    Bracts in plantain (Plantago)
    NA
    Final leaf segment length (compound lvs only)
    10–30 mm
    Final leaf segment length to width ratio (compound lvs only)
    2
    Final leaf segment width (compound lvs only)
    5–10 mm
    Floral bract texture
    the floral bracts are thin, dry and papery, possibly with a narrow green stripe at the center
    Floral bracts
    the flower has one or more bracts associated with it
    Flower bract length
    2–5 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)
    Leaf blade bloom
    the underside of the leaf has no noticeable bloom
    Leaf blade edges
    • the edge of the leaf blade has lobes, or it has both teeth and lobes
    • the edge of the leaf blade has teeth
    Leaf blade hairs
    NA
    Leaf blade length
    100–300 mm
    Leaf blade primary vein pattern
    the secondary veins branch off at intervals from the primary vein
    Leaf blade shape
    • 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 triangular, with the stalk or attachment point on one of the sides
    Leaf blade surface colors
    the upper side of the leaf blade is relatively uniform in color
    Leaf blade width
    60–280 mm
    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 spines
    there are no spines on the leaf edges
    Leaf stalk
    the leaves have leaf stalks
    Leaf stalk attachment to leaf
    the petiole attaches at the basal margin of the leaf blade
    Leaf stalk base
    the petiole base clasps the stem or sheathes the stem
    Leaf stalk length
    70–250 mm
    Leaf teeth and lobes
    • the leaf blade margin has forward-pointing teeth
    • the leaf blade margin has rounded teeth
    Leaf type
    the leaves are compound (made up of two or more discrete leaflets
    Leaf variation
    the leaves are nearly similar in size, prominence of teeth, and length of stalks throughout the stem
    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

  • Place

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

  • 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
    50–250 cm
    Stem hair distribution
    NA
    Stem orientation
    the stems are upright or angled outwards
    Stem roughness between nodes
    the stem does not feel rough
    Tendril origin
    NA
    Tendrils
    the plant does not have tendrils
    Wings on stem
    the stem does not have wings on it

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
present
Vermont
present

Conservation status

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

Massachusetts
not applicable (S-rank: SNA)

From Flora Novae Angliae dichotomous key

1.  Conium maculatum L. E

poison-hemlock. CT, MA, ME, NH, RI, VT. Roadsides, fields, waste areas.

Native to North America?

No

Family

Apiaceae

Genus

Conium