Weed Seed: Tripleurospermum inodorum (Scentless chamomile)

Family

Asteraceae

Common Name

Scentless chamomile

Regulation

Secondary Noxious, Class 3 and Noxious, Class 5 in the Canadian Weed Seeds Order, 2016 under the Seeds Act.

Distribution

Canadian: Occurs in throughout Canada except in NU (Brouillet et al. 2016Footnote 1).

Worldwide: Native to Europe and temperate Asia and introduced in North and South America, the Azores, Poland, Russian Federation (Primorye), and New Zealand (USDA-ARS 2016Footnote 2). In the United States, widespread in the north but absent from much of the south (USDA-NRCS 2016Footnote 3).

Duration of Life Cycle

Annual to short-lived perennial

Seed or Fruit Type

Achene

Identification Features

Size

  • Achene length: 1.7 - 3.1 mm
  • Achene width: 0.7 - 1.6 mm

Shape

  • Rectangular-shaped achene

Surface Texture

  • Three ribs are on one side, and no ribs on other side of achene
  • Surface is transversely wrinkled between ribs

Colour

  • Ribs are light to medium brown, dark brown between ribs, resin glands are reddish

Other Features

  • Achene has 2 ends: top has a small style peg surrounded by a jagged rim, while bottom has a small ring
  • Two resin glands are at top of achene on side without ribs
  • Resin glands usually round and reddish
  • Resin glands can also be seen looking down from top of achene

Habitat and Crop Association

Cultivated fields, old fields, pastures, hay fields, farm yards, fencelines, gardens, lawns, ditches, roadsides, railway lines and disturbed areas (Woo et al. 1991Footnote 4, Darbyshire 2003Footnote 5).

General Information

Scentless chamomile was recorded in Canada in the late 1800s and is believed to have arrived in ship ballast, as a garden plant, and as a seed contaminant from Europe (Woo et al. 1991Footnote 4).

Dense stands of scentless chamomile have approximately 3200 flower heads and may produce up to 1.8 million achenes per square meter (Woo et al. 1991Footnote 4). These achenes can remain viable in the soil for up to about 10 years (Woo et al. 1991Footnote 4).

Similar Species

False mayweed (Tripleurospermum maritimum)

  • False mayweed achenes are a similar size, brown colour, and rectangular shape as scentless chamomile. The rib arrangement and the resin glands are also similar to scentless chamomile.
  • False mayweed achenes usually have less space between the ribs, the resin glands cannot be seen from the top of the achene, and the resin glands are often brown and oval rather than round and reddish compared to scentless chamomile.

Photos

Scentless chamomile (Tripleurospermum inodorum) achenes
Scentless chamomile (Tripleurospermum inodorum) achene, side with ribs
Scentless chamomile (Tripleurospermum inodorum) achene, side without ribs
Scentless chamomile (Tripleurospermum inodorum) achene, side view
Scentless chamomile (Tripleurospermum inodorum) achene, top-down view

Similar species

Similar species: False mayweed (Tripleurospermum maritimum) achenes
Similar species: False mayweed (Tripleurospermum maritimum) achene, side with ribs
Similar species: False mayweed (Tripleurospermum maritimum) achene, side without ribs
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