Tripleurospermum inodorum (Scentless False Mayweed)

Plant Info
Also known as: Scentless Chamomile, False Chamomile
Genus:Tripleurospermum
Family:Asteraceae (Aster)
Life cycle:annual, short-lived perennial
Origin:Europe
Status:
  • Weedy
Habitat:sun; disturbed soil; roadsides, fields, dry shorelines, lawns, waste places
Bloom season:May - September
Plant height:8 to 32 inches
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 7+petals Cluster type: panicle

[photo of flowers] Daisy-type flowers, single at the tips of branching stems. Flowers are 1 to 2 inches across with 10 to 25 white petals (ray flowers) and a golden yellow center disk that expands from button-shaped to dome-shaped to nearly round as it matures. The rays droop as the disk expands, bent straight down at maturity before wilting away. The disk is solid at the core.

[photo of bracts] The bracts surrounding the base of the flower are narrowly lance-oblong, darker green to brownish down the center with a narrow band of pale membranous edging but darker brown at the tip. Bracts and flower stalks are hairless, sometimes sparsely hairy when young.

Leaves and stems: Leaf attachment: alternate Leaf type: compound Leaf type: lobed

[photo of leaves] Leaves are ¾ to 3 inches long, feathery with a few to numerous thread-like branching lobes. Stems are single, erect, branched in the upper plant, weakly ridged or lined, hairless though sparsely hairy when young.

Fruit: Fruit type: seed without plume

The center disk becomes a round head of dry, brown seed that lack tufts of hair. Seeds are triangular in cross-section, have 3 to 5 ribs, and a minutely textured surface between the ribs (magnification required).

Notes:

Scentless False Mayweed, also known by synonyms Matricaria perforata and Tripleurospermum maritimum subsp. inodorum, is similar to the also-weedy Dog Fennel (Anthemis cotula) and Matricaria species. Dog Fennel has leaves that are pinnately lobed (divisions on opposite sides of a common stalk), have broader and flatter lobes, and a distinct, unpleasant odor when crushed. While the Maticaria species have very similar feathery and thread-like leaves, the seeds are not triangular in cross-section and are smooth between the 5 ribs. Also, Pineapple-weed (M. discoidea) lacks ray flowers, and German Chamomile (M. chamomilla a.k.a. M. recutita) has a flower disk with a hollow core and typically has multiple stems. Feel free to rip the disks open and see whether they're hollow or solid. These are all weeds, after all.

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More photos

Photos by K. Chayka taken in Lake and St. Louis counties. Photos courtesy Peter M. Dziuk taken in Lake and St. Louis counties and in North Dakoka.

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