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

Triosteum angustifolium — lesser horse-gentian

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Facts

Lesser horse-gentian is native to southern and eastern North America. It is rare in New England at the northeastern limit of its range, and can be found only in western Connecticut in rocky forests and woodlands, ledges and railroads.

Habitat

Forests, ridges or ledges, talus and rocky slopes, 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
Flower petal color
  • green to brown
  • yellow
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 is only one way to evenly divide the flower (the flower is bilaterally 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 fleshy
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 symmetry
    there are two or more ways to evenly divide the calyx (the calyx is radially symmetrical)
    Carpels fused
    the carpels are fused to one another
    Cleistogamous flowers
    there are no cleistogamous flowers on the plan
    Corolla palate
    no
    Corona lobe length
    0 mm
    Epicalyx
    the flower does not have an epicalyx
    Epicalyx number of parts
    0
    Flower description
    the flower has an inferior ovary, with or without a hypanthium
    Flower petal color
    • green to brown
    • yellow
    Flower reproductive parts
    the flower has both pollen- and seed-producing parts
    Flower symmetry
    there is only one way to evenly divide the flower (the flower is bilaterally symmetrical)
    Flowers sunken into stem
    no
    Form of style
    • the style is knob-like at the tip, and unbranched
    • the style is lobed at the tip, and unbranched
    Fusion of sepals and petals
    the petals or the sepals are fused into a cup or tube
    Horns in hoods (Asclepias)
    NA
    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
    Inner tepals (Rumex)
    NA
    Nectar spur
    the flower has no nectar spurs
    Number of pistils
    1
    Number of sepals, petals or tepals
    there are five petals, sepals, or tepals in the flower
    Ovary position
    the ovary is below the point of petal and/or sepal attachment
    Petal and sepal arrangement
    the flower includes two cycles of petal- or sepal-like structures
    Petal and sepal colors
    • green to brown
    • yellow
    Petal appearance
    the petals are thin and delicate, and pigmented (colored other than green or brown)
    Petal folds or pleats
    the petals of the flower do not have folds or plaits
    Petal hairs (Viola)
    NA
    Petal number
    5
    Petal tips (Cuscuta)
    NA
    Scales inside corolla
    no
    Sepal and petal color
    the sepals are different from the petals
    Sepal appendages
    the sepals do not have appendages on them
    Sepal appendages (Oenothera)
    NA
    Sepal number
    5
    Stamen attachment
    the stamens are attached at or near the bases of the petals or tepals
    Stamen number
    5
    Stamen position relative to petals
    the stamens are lined up with the sepals
    Staminodes
    there are no staminodes on the flower
    Umbel flower reproductive parts
    NA
    Upper lip of bilabiate corolla
    • NA
    • the upper lip of the bilabiate corolla has two lobes

  • Fruits or seeds

    Achene relative orientation
    NA
    Achene shape
    NA
    Achene surface (Polygonum)
    NA
    Achene type
    NA
    Berry color
    • orange
    • red
    Capsule color (Viola)
    NA
    Capsule ribs
    NA
    Capsule splitting
    NA
    Fruit (pyxis) dehiscence
    NA
    Fruit beak length
    0 mm
    Fruit features (Brassicaceae)
    NA
    Fruit locules
    four
    Fruit type (general)
    the fruit is fleshy
    Fruit type (specific)
    the fruit is a drupe (fleshy, with a firm inner ovary wall that encloses a single seed)
    Legumes (Fabaceae)
    NA
    Mericarp length
    0 mm
    Mericarp segment shape (Desmodium)
    NA
    Other markings on berry
    the ripe berries are mostly one color without spots or streaks
    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
    NA
    Schizocarpic fruit segments
    0
    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 clear and watery
    Sap color
    the sap is clear

  • Growth form

    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
    Spines on plant
    the plant has no spines

  • Leaves

    Bracteole number (Apiaceae)
    0
    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
    Final leaf segment width (compound lvs only)
    0 mm
    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
    Leaf arrangement
    opposite: there are two leaves per node along the stem
    Leaf blade base
    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 edges
    the edge of the leaf blade is entire (has no teeth or lobes)
    Leaf blade length
    80–180 mm
    Leaf blade shape
    • the leaf blade is oblanceolate (lance-shaped, but with the widest point above the middle of the leaf blade)
    • 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 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 spines
    there are no spines on the leaf edges
    Leaf type
    the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
    Leaflet petiolules
    NA
    Leaves per node
    there are two leaves per node along the stem
    Specific leaf type
    the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
    Stipels
    NA
    Stipule features
    NA
    Stipules
    there are no stipules on the plant

  • Place

    Habitat
    terrestrial
    New England state
    Connecticut
    Specific habitat
    • forests
    • ridges or ledges
    • talus or rocky slopes
    • woodlands

  • Scent

    Plant odor
    the plant does not have much of a smell

  • Stem, shoot, branch

    Branched tendrils
    NA
    Hairs between stem nodes
    at least some of the hairs on the stem have glands
    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
    30–80 cm
    Tendril origin
    NA
    Tendrils
    the plant does not have tendrils

Wetland status

Occurs in wetlands or non-wetlands. (Wetland indicator code: FAC)

In New England

Distribution

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

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)

var. eamesii

Connecticut
historical (S-rank: SH)

From Flora Novae Angliae dichotomous key

1.  Triosteum angustifolium L. NC

lesser horse-gentian. CT; western portion of state. Rocky forests and woodlands, ledges, railroads.

1×2. Triosteum angustifolium × Triosteum aurantiacum → Triosteum ×‌eamesii (Wieg.) A. Haines is a rare horse-gentian hybrid that is known from CT and was formerly treated as Triosteum angustifolium var. eamesii Wieg. It most resembles T. angustifolium due to its short sepals and long-pubescent stems. It has leaf blades mostly 2.2–3.2 times a long as wide that are moderately puberulent abaxially and dried stems (3–) 4–7 mm thick at the midpoint (vs. leaf blades mostly 3.5–7 times as long as wide that are sparsely pubescent abaxially and dried stems 2–2.7 mm thick at the midpoint in T. angustifolium). Recognition of this hybrid shows T. angustifolium to be far more rare than previously believed because many collections of T. angustifolium were of the var. eamesii (i.e., they were hybrid plants).

Native to North America?

Yes

Sometimes confused with

Triosteum aurantiacum:
sepals 10–18 mm long, the margins and abaxial surface pubescent with hairs of uniform length, stem pubescent with hairs up to 2 mm long, and leaf blades 4–15 cm wide (vs. T. angustifolium, with sepals 9–12 mm long, conspicuously hispid-ciliate, the abaxial surface glabrous or short-pubescent, stem long-pubescent, the longer hairs 1.5–3 mm long, and leaf blades 2–6 cm wide).
Triosteum perfoliatum:
sepals 10–18 mm long, the margins and abaxial surface pubescent with hairs of uniform length, stem pubescent with hairs up to 1.5 mm long, and leaf blades 4–15 cm wide, the middle ones gamophyllous (vs. T. angustifolium, with sepals 9–12 mm long, conspicuously hispid-ciliate, the abaxial surface glabrous or short-pubescent, stem long-pubescent, the longer hairs 1.5–3 mm long, and leaf blades 2–6 cm wide, none gamophyllous).

Family

Caprifoliaceae

Genus

Triosteum