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

Scleranthus annuus — annual knawel, German knotgrass

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Facts

Annual knawel is native to Europe where it is a frequent weed of crops. Flower essences of annual knawel are occasionally used by herbalists to treat indecision or mood swings.

Habitat

Anthropogenic (man-made or disturbed habitats), 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
NA
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 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
  • 10
  • 5
  • 6
  • 7
  • 8
  • 9
Fruit type (general)
the fruit is dry but does not split open when ripe
Fruit length
3.2–5 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)
    Cilia on petals
    NA
    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 appearance
    NA
    Flower description
    the flower has a superior ovary and a hypanthium
    Flower length
    3–4.2 mm
    Flower number
    2–5
    Flower petal color
    NA
    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
    Fringed petal edges
    NA
    Fused stamen clusters
    NA
    Fusion of sepals and petals
    both the petals and sepals are separate and not fused
    Hairs on flower stalk
    NA
    Horns in hoods (Asclepias)
    NA
    Hypanthium
    the flower has a hypanthium
    Hypanthium length
    1.2–2 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
    3–15 mm
    Inner tepals (Rumex)
    NA
    Interior flower disk
    the flower has an interior disc
    Length of flower stalk
    0 mm
    Marks on petals
    • NA
    • there are no noticeable marks on the petals
    Nectar spur
    the flower has no nectar spurs
    Number of branches in umbel
    0
    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 above 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
    green to brown
    Petal appearance
    NA
    Petal base
    NA
    Petal folds or pleats
    NA
    Petal glandular dots or scales
    NA
    Petal hairs (Viola)
    NA
    Petal hairs on inner/upper surface
    NA
    Petal length
    0 mm
    Petal length relative to sepals
    NA
    Petal nectaries
    NA
    Petal number
    0
    Petal shape
    NA
    Petal tip shape
    NA
    Petal tips (Cuscuta)
    NA
    Petal width
    0 mm
    Raceme attachment (Veronica)
    NA
    Reproductive system
    all the flowers have both carpels and stamens (synoecious)
    Scales inside corolla
    NA
    Sepal and petal color
    NA
    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 cilia
    the sepals do not have cilia
    Sepal color
    green to brown
    Sepal length
    1.5–4 mm
    Sepal number
    5
    Sepal orientation
    • the sepals are pressed against the corolla, or jutting stiffly upward
    • the sepals are slightly curved outwards from the corolla
    Sepal relative length
    NA
    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
    • the sepals are thin and dry, paperlike
    Sepal tip shape
    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 separate from one another
    Stamen attachment
    the stamens are not attached to the petals or tepals
    Stamen number
    • 10
    • 5
    • 6
    • 7
    • 8
    • 9
    Stamen position relative to petals
    NA
    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
    0.8–1 mm
    Style petal-like
    the styles are not petal-like
    Surface of ovary
    the ovary surface is textured with tiny points, bumps or wrinkles
    Umbel flower reproductive parts
    NA
    Upper lip of bilabiate corolla
    NA

  • Fruits or seeds

    Achene shape
    • the achenes are another shape in outline
    • the achenes are oval in outline
    Achene surface (Polygonum)
    NA
    Achene type
    the fruit is an achene (dry, indehiscent, and usually one-seeded)
    Berry color
    NA
    Capsule color (Viola)
    NA
    Capsule ribs
    NA
    Capsule splitting
    NA
    Carpel beak length
    0 mm
    Fruit (pyxis) dehiscence
    NA
    Fruit features (Brassicaceae)
    NA
    Fruit length
    3.2–5 mm
    Fruit length relative to sepals
    the fruit is shorter than its associated sepals
    Fruit locules
    one
    Fruit shape
    the fruit is ovoid (egg-shaped)
    Fruit stalk orientation
    NA
    Fruit type (general)
    the fruit is dry but does not split open when ripe
    Fruit type (specific)
    the fruit is an achene (dry, usually one-seeded, does not separate or split open at maturity)
    Fruit width
    1 mm
    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
    Rows of seeds in fruit (Brassicaceae)
    NA
    Schizocarpic fruit compression
    NA
    Schizocarpic fruit segments
    0
    Seed length
    1.4–1.6 mm
    Seed number
    1
    Seed relative length
    the seed is about as long as it is wide
    Seed surface
    the seed is smooth or without clear markings
    Seeds comose
    no hairs
    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 not parasitic
    Plant color
    the leaves or young stems of the plant are green
    Spines on plant
    the plant has no spines
    Underground organs
    • there are only slender roots on the plant
    • 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
    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
    the floral bracts are green, with a leaf-like texture
    Floral bracts
    the flower has one or more bracts associated with it
    Hairs on leaf stalk
    NA
    Hooked hairs on underside of leaf
    no
    Leaf arrangement
    opposite: there are two leaves per node along the stem
    Leaf blade base
    the leaf has no stalk
    Leaf blade bloom
    the underside of the leaf has no noticeable bloom
    Leaf blade edges
    the edge of the leaf blade is entire (has no teeth or lobes)
    Leaf blade length
    3–24 mm
    Leaf blade primary vein pattern
    the secondary veins branch off at intervals from the primary vein
    Leaf blade shape
    • the leaf blade is linear (very narrow with more or less parallel sides)
    • 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 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
    0.5 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 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 no leaf stalks, but attach directly to the stem
    Leaf stalk attachment to leaf
    NA
    Leaf stalk base
    NA
    Leaf stalk length
    0 mm
    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 acute (sharply pointed)
    • the tip of the leaf blade is obtuse (bluntly pointed)
    Leaf type
    the leaves are simple (i.e., lobed or unlobed but not separated into leaflets)
    Leaf types
    • NA
    • 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 are two leaves 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
    New England state
    • Connecticut
    • Maine
    • Massachusetts
    • New Hampshire
    • Rhode Island
    • Vermont
    Specific habitat
    • man-made or disturbed habitats
    • meadows or fields

  • Scent

    Plant odor
    the plant does not have much of a smell

  • Stem, shoot, branch

    Branched tendrils
    NA
    Direction of stem hairs
    the hairs point downwards, or they bend outwards and then downwards
    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
    Hairs between stem nodes
    the hairs on the stem are plain, without glands or branches, and not tangled
    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
    2–25 cm
    Stem bloom
    there is no powdery or waxy film on the stem
    Stem hair distribution
    the hairs on the stem are arranged in lines running down the stem from the edges of the leaf bases
    Stem nodes swollen
    the stem is swollen at the nodes
    Stem orientation
    • the stems are upright or angled outwards
    • the stems trail at the base, but may turn upwards at the tips
    Stem roughness between nodes
    the stem does not feel rough
    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

Usually occurs in non-wetlands, but occasionally in wetlands. (Wetland indicator code: FACU)

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.  Scleranthus annuus L. E

annual knawel. CT, MA, ME, NH, RI, VT. Dry, open, sandy areas such as roadsides, yards, and 
dry fields.

Native to North America?

No

Sometimes confused with

Polycarpon tetraphyllum:
leaves elliptic to ovate or obovate, with stipules, and capsule with many seeds (vs. S. annuus, with leaves linear, without stipules, and fruit a one-seeded utricle).
Scleranthus perennis:
sepals obtuse to rounded at apex, usually introrse in fruit and overlapping, with a broader white-scarious margin 0.3–0.5 mm wide, and floral bracts mostly shorter than flowers (vs. S. annuus, with sepals acute at the apex, spreading to erect in fruit, separate, with a narrow, white-scarious margin up to 0.1 mm wide, and floral bracts equaling or exceeding than flowers).

Family

Caryophyllaceae

Genus

Scleranthus