Rorippa palustris — common yellow-cress

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 attachment

  the anther is attached by its base to the filament

  Anther color

  the anthers show no hint of a pink, reddish or purplish tint

  Anther length

  0.3–0.5 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

  Anther tube length

  0 mm

  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

  Corona lobe length

  0 mm

  Epicalyx

  the flower does not have an epicalyx

  Epicalyx number of parts

  0

  Filament length

  1–2.5 mm

  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 diameter

  2 mm

  Flower number

  20–30

  Flower orientation

  the flower points upwards or is angled outwards

  Flower petal color

  yellow

  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 knob-like at the tip, and unbranched

  Fringed petal edges

  the petals are not fringed

  Fused stamen clusters

  NA

  Fusion of sepals and petals

  both the petals and sepals are separate and not fused

  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

  Hypanthium length

  0 mm

  Inflorescence length

  Up to 200 mm

  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

  the flower does not have an interior disc

  Length of flower stalk

  2.5–14 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

  0

  Number of carpels

  2

  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

  Perianth shape

  the perianth is rotate (platter-shaped, the corolla flattened, circular, with nearly horizontally spreading lobes)

  Petal and sepal arrangement

  the flower includes two cycles of petal- or sepal-like structures

  Petal and sepal colors

  yellow

  Petal appearance

  the petals are thin and delicate, and pigmented (colored other than green or brown)

  Petal base

  the petal narrows abruptly 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

  1.5–3 mm

  Petal length relative to sepals

  the petals are about equal in length to the sepals

  Petal nectaries

  the petals do not have nectaries

  Petal number

  4

  Petal shape

  the petal outline is spatulate (spoon-shaped; narrow near the base, then suddenly widening to a rounded tip)

  Petal tip shape

  the petal tip is obtuse (bluntly pointed)

  Petal tips (Cuscuta)

  NA

  Petal width

  0.5–2 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
  • the sepals resemble petals in color and 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
  • yellow

  Sepal features

  the sepals do not have any of the mentioned special features

  Sepal length

  1.5–2.6 mm

  Sepal number

  4

  Sepal orientation

  the sepals are pressed against the corolla, or jutting stiffly upward

  Sepal relative length

  NA

  Sepal shape

  the sepal outline is oblong (rectangular, but with rounded ends)

  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 obtuse (is bluntly pointed)

  Sepal uniformity

  all the sepals are about the same size

  Sepals fused only to sepals

  the sepals are separate from one another

  Spur length

  0 mm

  Spur number

  NA

  Stamen appendages

  stamen appendages are absent

  Stamen attachment

  the stamens are not attached to the petals or tepals

  Stamen length

  1.3–2.8 mm

  Stamen lengths differ

  the stamens are tetradynamous (four long stamens and two short ones)

  Stamen morphology

  the stamens within a cycle differ in length or width

  Stamen number

  6

  Stamen position relative to petals

  NA

  Stamen relative length

  anything

  Stamens fused

  the stamens are not attached to one another

  Staminodes

  there are no staminodes on the flower

  Stigma position

  the stigmas are positioned at the tip of the style

  Style length

  0.2–1.2 mm

  Style petal-like

  the styles are not petal-like

  Style relative length

  NA

  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

  Carpel beak length

  0 mm

  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

  2.5–10 mm

  Fruit length relative to sepals

  NA

  Fruit length to width ratio

  1.7–2.9

  Fruit locules

  two

  Fruit shape

  • the fruit is ellipsoid (widest in the middle and tapering to each end)
  • the fruit is obloid (longer than wide and with rounded ends)
  • the fruit is ovoid (egg-shaped)

  Fruit stalk orientation

  • the fruits curve or droop downwards
  • 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 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)

  Fruit width

  1.5–3.5 mm

  Hair type on fruit

  NA

  Hairs on fruit

  the fruits are not hairy

  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

  Ovary stipe length

  0 mm

  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

  Relative fruit length

  0

  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

  Seed length

  0.5–0.9 mm

  Seed number

  44–60

  Seed relative length

  • the seed is about as long as it is wide
  • the seed is longer than it is wide

  Seed surface

  • the seed is covered with short, round or cylindrical projections (papillae)
  • the seed is hairless

  Seeds comose

  no hairs

  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

  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
  • 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 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

  Floral bract texture

  NA

  Floral bracts

  the flower does not have bracts

  Flower bract length

  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

  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)
  • the leaf has no stalk

  Leaf blade base shape

  • the base of the leaf blade is cordate (heart-shaped, has rounded lobes at the base)
  • the base of the leaf blade is cuneate (wedge-shaped, tapers to the base with relatively straight, converging edges), or narrow
  • the base of the leaf blade is sagittate (arrow-shaped, with pointed lobes directed backwards)

  Leaf blade base symmetry

  the leaf blade base is asymmetrical

  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
  • the edge of the leaf blade is entire (has no teeth or lobes)

  Leaf blade flatness

  the leaf is flat (planar) at the edges

  Leaf blade hairs

  the leaf blade has simple hairs with no glands, and not tangled or wooly

  Leaf blade length

  15–300 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 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 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 blade width

  5–80 mm

  Leaf duration

  • the leaves drop off in winter (or they whither but persist on the plant)
  • the leaves remain green all winter

  Leaf form

  the leaves are green, with an expanded blade and a leaf-like texture

  Leaf hair orientation

  the hairs are standing up straight or curved in different directions

  Leaf sheath length

  0 mm

  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 leaf stalks
  • the leaves have no leaf stalks, but attach directly to the stem

  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
  • 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)
  • the leaf blade margin has forward-pointing teeth
  • the leaf blade margin has outward-pointing teeth
  • the leaf blade margin has rounded teeth
  • the leaf blade margin is wavy, but does not have teeth
  • the leaf has a row of two or more lobes on each side of the central axis

  Leaf tip

  • the tip of the leaf blade is acute (sharply pointed)
  • the tip of the leaf blade is obtuse (bluntly pointed)

  Leaf tufts in axils

  there are no clusters of smaller leaves growing out of axils

  Leaf type

  • the leaves are compound (made up of two or more discrete leaflets
  • 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

  0–15

  Leaflet petiolules

  the leaflets of the compound leaf lack petiolules

  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
  • the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)

  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

  • aquatic
  • terrestrial
  • wetlands

  New England state

  • Connecticut
  • Maine
  • Massachusetts
  • New Hampshire
  • Rhode Island
  • Vermont

  Specific habitat

  • brackish or salt marshes and flats
  • edges of wetlands
  • fresh tidal marshes or flats
  • in rivers or streams
  • man-made or disturbed habitats
  • marshes
  • shores of rivers or lakes
  • swamps

• Stem, shoot, branch

  Branched tendrils

  NA

  Direction of stem hairs

  the hairs point mostly upwards to outwards

  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 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

  5–140 cm

  Stem bloom

  there is no powdery or waxy film on the stem

  Stem hair distribution

  the hairs on the stem are distributed more of less uniformly

  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 wetlands. (Wetland indicator code: OBL)

In New England

From Flora Novae Angliae dichotomous key