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

Draba arabisans — rock whitlow-mustard

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Facts

Rock whitlow-mustard is native to the northeastern portion of North america, but enters New England only in the northernmost portions of Maine and Vermont. It is rare native of cliffs, talus and headlands on high-pH bedrock. The common name 'whitlow' refers to an inflammation of the finger and toenail areas (also occurring in the hoofs of cattle), for which this species was thought to be a cure.

Habitat

Cliffs, balds, or ledges, ridges or ledges, talus and rocky slopes

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
  • Maine
  • Vermont
Flower petal color
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 has teeth
  • 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
both the petals and sepals are separate and not fused
Stamen number
6
Fruit type (general)
the fruit is dry and splits open when ripe
Fruit length
5–14 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 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 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 a superior ovary, and lacks a hypanthium
    Flower petal color
    white
    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 knob-like at the tip, and unbranched
    Fused stamen clusters
    NA
    Fusion of sepals and petals
    both the petals and sepals are separate and not fused
    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 four petals, sepals, or tepals in the flower
    Number of styles
    0–1
    Ovary position
    the ovary is above 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
    white
    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
    4
    Petal tips (Cuscuta)
    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 appendages
    the sepals do not have appendages on them
    Sepal appendages (Oenothera)
    NA
    Sepal number
    4
    Stamen attachment
    the stamens are not attached to the petals or tepals
    Stamen number
    6
    Stamen position relative to petals
    NA
    Staminodes
    there are no staminodes on the flower
    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
    • the capsule splits by two main valves, teeth or pores
    Fruit (pyxis) dehiscence
    NA
    Fruit features (Brassicaceae)
    NA
    Fruit length
    5–14 mm
    Fruit locules
    two
    Fruit type (general)
    the fruit is dry and splits open when ripe
    Fruit type (specific)
    • the fruit is a silicle (similar to a silique, but less than or equal to three times as long as wide)
    • the fruit is a silique (greater than three times as long as wide, and dehisces by two valves, leaving the persistent replum to which the seeds are attached, found only in the Brassicaceae)
    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 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)
    there are two or more rows of seeds in each locule of the fruit
    Schizocarpic fruit compression
    NA
    Schizocarpic fruit segments
    0
    Septum in fruit (Brassicaceae)
    The fruit is either not compressed or is compressed parallel to the septum; therefore, the fruit and its septum are about the same width
    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
    Plants darken when dry
    no
    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
    Hairs on underside of leaf
    the underside of the leaf is fuzzy or hairy
    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
    Leaf blade edges
    • the edge of the leaf blade has teeth
    • the edge of the leaf blade is entire (has no teeth or lobes)
    Leaf blade length
    10–60 mm
    Leaf blade shape
    • the leaf blade is linear (very narrow with more or less parallel sides)
    • the leaf blade is oblanceolate (lance-shaped, but with the widest point above the middle of the leaf blade)
    • the leaf blade is oblong (rectangular but with rounded ends)
    • the leaf blade is ovate (widest below the middle and broadly tapering at both ends)
    • the leaf blade is spatulate (spoon-shaped; narrow near the base, then suddenly widening to a rounded tip)
    Leaf blade surface colors
    the upper side of the leaf blade is relatively uniform in color
    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 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 type
    the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
    Leaf variation
    the lower leaves are larger, toothier, and/or on longer stalks than the upper leaves
    Leaves per node
    there is one leaf 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
    • Maine
    • Vermont
    Specific habitat
    • cliffs, balds, or ledges
    • ridges or ledges
    • talus or rocky slopes

  • 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
    Hairs between stem nodes
    at least some of the hairs on the stem are branched
    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
    5–45 cm
    Stem roughness between nodes
    the stem does not feel rough
    Tendril origin
    NA
    Tendrils
    the plant does not have tendrils

Wetland status

Not classified

In New England

Distribution

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

Conservation status

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

Maine
extremely rare (S-rank: S1), threatened (code: T)
Vermont
rare to uncommon (S-rank: S2S3)

From Flora Novae Angliae dichotomous key

1.  Draba arabisans Michx. NC

rock whitlow-mustard. Draba incana L. var. arabisans (Michx.) S. Wats. • ME, VT. Cliffs, talus, and headlands in high-pH bedrock regions, ascending to subalpine situations in northern VT.

Native to North America?

Yes

Sometimes confused with

Draba cana:
lowest 1–3 flowers each subtended by a leafy bract and siliques pubescent with stellate hairs (vs. D. arabisans, with none of the flowers subtended by leafy bracts and siliques glabrous or sparsely pubescent with simple or forked hairs).
Draba glabella:
basal leaf blades with stalked stellate hairs and stigmas often bilobed (vs. D. arabisans, with basal leaf blades with sessile stellate hairs and stigmas scarecely lobed).

Synonyms

  • Draba incana L. var. arabisans (Michx.) S. Wats.

Family

Brassicaceae

Genus

Draba