Weed Seed: False mayweed (Tripleurospermum maritimum subsp. maritimum)

Family

Asteraceae

Synonyms

Matricaria maritima

Distribution in Canada

Found in ON, QC, NB, NS, NL

Duration of life cycle

Perennial (occasionally biennial)

Seed/Fruit type

Achene - a one-seeded, dry fruit

Seed identification features

Size

  • length: 2.0–3.5 mm
  • width: 1.0–1.5 mm

Shape

  • in outline: rectangular
  • in cross-section: square
  • three ribs evident on one side (no ribs on the other side)

Surface texture

  • smooth on ribs, bumpy between ribs
  • ribs tend to be close together
  • overall sheen

Colour

  • ribs are medium brown (occasionally light)
  • dark brown between ribs

Other structures

  • achene has 2 ends
    • top has a small peg surrounded by a jagged rim
    • bottom has a small ring
  • 2 depressions occasionally appear at the top of the achene on the non-rib side (dark brown or red, usually oval-shaped)

Similar species

Scentless chamomile (Tripleurospermum maritimum subsp. inodorum)

  • found across Canada and the northern United States
  • similar to false mayweed in size (scentless chamomile tends to be ~0.5 mm smaller), rectangular shape, colour, markings and the presence of ribs (it is difficult to distinguish from false mayweed with accuracy)
  • tends to have wider spaces between ribs
  • 2 dots on the non-rib side are round

Photos

Photo - False mayweed (Tripleurospermum maritimum subspecies Maritimum) seed (showing 3 ribs)
False mayweed (Tripleurospermum maritimum subsp. maritimum) seed (showing 3 ribs)
Photo - False mayweed (Tripleurospermum maritimum subspecies Maritimum) (opposite side of seed with no ribs—note oval resin dots)
False mayweed (Tripleurospermum maritimum subsp. maritimum) (opposite side of seed with no ribs—note oval resin dots)
Photo - False mayweed (Tripleurospermum maritimum subspecies Maritimum) seeds
False mayweed (Tripleurospermum maritimum subsp. maritimum) seeds

Similar species

Photo - Similar species: Scentless chamomile (Tripleurospermum maritimum subspecies inodorum) seed (showing 3 ribs)
Similar species: Scentless chamomile (Tripleurospermum maritimum subsp. inodorum) seed (showing 3 ribs)
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