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

Bartonia iodandra — purple screwstem

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Facts

Purple screwstem is a rare northeastern endemic found only in New England and eastern Canada. It inhabits swamps, peatlands, meadows and abandoned borrow pits. It is very similar in appearance to the much more common twining screwstem (Bartonia paniculata).

Habitat

Anthropogenic (man-made or disturbed habitats), bogs, fens, meadows and fields, 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
Flower petal color
  • pink to red
  • white
Leaf type
the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
Leaf arrangement
alternate: there is one leaf 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 four 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
4
Fruit type (general)
the fruit is dry and splits open when ripe
Fruit length
4–6 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 color
    there is a noticeable pink, reddish or purplish tint to the anthers
    Anther length
    0.4–1 mm
    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)
    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
    • the petal margins have cilia
    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
    Filament length
    0.5–1 mm
    Filament surface
    the filament is smooth, with no hairs or scales
    Flower description
    the flower has a superior ovary, and lacks a hypanthium
    Flower diameter
    0.8–2 mm
    Flower length
    3–6.2 mm
    Flower orientation
    the flower points upwards or is angled outwards
    Flower petal color
    • pink to red
    • 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 style is lobed at the tip, and unbranched
    Fused stamen clusters
    NA
    Fusion of sepals and petals
    the petals or the sepals are fused into a cup or tube
    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
    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
    Interior flower disk
    NA
    Marks on petals
    there are no noticeable marks on the petals
    Nectar spur
    the flower has no nectar spurs
    Number of carpels
    2
    Number of sepals, petals or tepals
    there are four 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 campanulate (bell-shaped, with a tube about as long as wide, flaring at the mouth)
    Petal and sepal arrangement
    the flower includes two cycles of petal- or sepal-like structures
    Petal and sepal colors
    • pink to red
    • 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 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 length
    3–6.2 mm
    Petal length relative to sepals
    the petals are about equal in length to the sepals
    Petal number
    4
    Petal shape
    • the petal outline is lanceolate (lance-shaped; narrow, gradually tapering from the base to the tip)
    • the petal outline is oblong (rectangular, but with rounded ends)
    Petal tip shape
    the petal tip is acute (sharply pointed)
    Petal tips (Cuscuta)
    NA
    Petal width
    0.8–2 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
    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
    • the sepals have cilia on their edges
    Sepal color
    • blue to purple
    • green to brown
    Sepal features
    one or more winged
    Sepal length
    1.5–3.2 mm
    Sepal number
    4
    Sepal orientation
    the sepals are pressed against the corolla, or jutting stiffly upward
    Sepal relative length
    the sepal lobes are longer than the fused portion
    Sepal shape
    • the sepal outline is lanceolate (lance-shaped; narrow, gradually tapering from the base to the tip)
    • the sepal outline is subulate (narrowly tapering from the base to the apex; awl-shaped)
    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 acuminate (tapers to a very narrow point)
    • the sepal tip is acute (is sharply pointed)
    Sepal uniformity
    all the sepals are about the same size
    Sepals fused only to sepals
    the sepals are fused to each other (not other flower parts), at least near their bases
    Spur length
    0 mm
    Spur number
    NA
    Stamen appendages
    stamen appendages are absent
    Stamen attachment
    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
    4
    Stamen position relative to petals
    the stamens are lined up with the sepals
    Stamen relative length
    anything
    Stamens fused
    the stamens are not attached to one another
    Staminodes
    there are no staminodes on the flower
    Stigma length
    0.8–1.5 mm
    Stigma position
    the stigmas are positioned in lines on the ovary
    Style petal-like
    the styles are not petal-like
    Style relative length
    the stigma does not protrude beyond the mouth of the corolla
    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 splitting
    the capsule splits by two main valves, teeth or pores
    Fruit (pyxis) dehiscence
    NA
    Fruit cross-section
    the fruit is round in cross-section
    Fruit features (Brassicaceae)
    NA
    Fruit length
    4–6 mm
    Fruit length relative to sepals
    the fruit is longer than its associated sepals
    Fruit locules
    one
    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 and splits open when ripe
    Fruit type (specific)
    the fruit is a capsule (splits along two or more seams, apical teeth or pores when dry, to release two or more seeds)
    Legumes (Fabaceae)
    NA
    Mericarp length
    0 mm
    Mericarp segment shape (Desmodium)
    NA
    Other markings on berry
    NA
    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 length
    0.15–0.1 mm
    Seed relative length
    the seed is about as long as it is wide
    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

    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 a parasite of fungi (mycoheterotrophic)
    Plant color
    the plant lacks green pigments, even on the leaves or young stems
    Plants darken when dry
    no
    Spines on plant
    the plant has no spines

  • Leaves

    Bracteole edges
    NA
    Bracteole length
    0 mm
    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
    Final leaf segment width (compound lvs only)
    0 mm
    Floral bract texture
    NA
    Floral bracts
    the flower does not have bracts
    Flower bract length
    0 mm
    Hairs on leaf stalk
    NA
    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
    Leaf arrangement
    alternate: there is one leaf per node along the stem
    Leaf blade bloom
    NA
    Leaf blade edges
    the edge of the leaf blade is entire (has no teeth or lobes)
    Leaf blade flatness
    NA
    Leaf blade hairs
    NA
    Leaf blade length
    0.5–4.5 mm
    Leaf blade primary vein pattern
    the secondary veins branch off at intervals from the primary vein
    Leaf blade shape
    the leaf blade is subulate (awl-shaped; narrowly tapering from the base to the tip)
    Leaf blade surface colors
    the upper side of the leaf blade is relatively uniform in color
    Leaf blade vein pattern
    NA
    Leaf duration
    the leaves drop off in winter (or they whither but persist on the plant)
    Leaf form
    the leaves are small and thin and lack leaf stalks
    Leaf hair orientation
    NA
    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
    Leaf stalk base
    NA
    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)
    Leaf tufts in 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 is one leaf 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 length
    0 mm
    Stipule shape
    NA
    Stipules
    there are no stipules on the plant
    Teeth per side of leaf blade
    0

  • Place

    Habitat
    • terrestrial
    • wetlands
    Specific habitat
    • bogs
    • fens
    • man-made or disturbed habitats
    • meadows or fields
    • swamps

  • Scent

    Plant odor
    the plant does not have much of a smell

  • Stem, shoot, branch

    Branched tendrils
    NA
    Direction of stem hairs
    NA
    Flowering stem cross-section
    • the flowering stem has strong or sharp angles, but is not square
    • 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
    NA
    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
    3–25 cm
    Stem hair distribution
    NA
    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 wetlands. (Wetland indicator code: OBL)

In New England

Distribution

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

Conservation status

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

New Hampshire
historical (S-rank: SH), endangered (code: E)
Rhode Island
extremely rare (S-rank: S1), concern (uncertain) (code: C*)

From Flora Novae Angliae dichotomous key

1.  Bartonia iodandra B. L. Robins. NC

purple screwstem. Bartonia paniculata (Michx.) Muhl. var. intermedia Fern.; B. paniculata (Michx.) Muhl. ssp. iodandra (B.L. Robins.) J. Gillett; B. paniculata (Michx.) Muhl. var. iodandra (B.L. Robins.) Fern.; B. paniculata (Michx.) Muhl. var. sabulonensis (Fern.) Fern.; B. virginica (L.) B.S.P. var. sabulonensis (Fern.) Boivin • MA, ME, NH, RI. Swamps, peatlands, abandoned borrow pits, meadows. Bartonia iodandra has been treated as a subspecies or variety of B. paniculata by most authors, likely due to similarities in leaf arrangement and stigma length. However, it possesses many character states that are transitional to B. virginica, including stem stature and coloration, petal shape and apex, anther apex, stamen color, and seed size. Gillett (1959) noted its probable hybrid origin. As such, it is inappropriate to ally it with one of its putative parents. Its occurrence in Newfoundland (beyond the range of its parents) and production of well-formed seeds support its recognition as a hybrid-derived species (rather than as an F₁ hybrid).

Native to North America?

Yes

Sometimes confused with

Bartonia paniculata:
petals lanceolate and acute at the apex, anthers usually yellow and mostly 0.3-0.5 mm long, and stems often slender, lax, and green (vs. B. iodandra, with petals oblong-lanceolate and acute at the apex or infrequently with an obscure apiculus, anthers usually purple and mostly 0.5-0.6 mm long, and stems stouter, strict, usually purple or purple tinged).
Bartonia virginica:
leaves opposite and stigmas mostly 1.5-2.3 mm long (vs. B. iodandra, with leaves alternate and stigmas 0.8-1.5 mm long).

Synonyms

  • Bartonia paniculata (Michx.) Muhl. ssp. iodandra (B.L. Robins.) J. Gillett
  • Bartonia paniculata (Michx.) Muhl. var. intermedia Fern.
  • Bartonia paniculata (Michx.) Muhl. var. iodandra (B.L. Robins.) Fern.
  • Bartonia paniculata (Michx.) Muhl. var. sabulonensis (Fern.) Fern.
  • Bartonia virginica (L.) B.S.P. var. sabulonensis (Fern.) Boivin

Family

Gentianaceae

Genus

Bartonia