Scentless camomile

Composite or Aster (Asteraceae family):

Tripleurospermum inodorum (L.) Sch. Bip.

EPPO code:

MATIN

Other names:

Scentless mayweed

Species information

Lifecycle:

Short lived perennial but occasionally an annual or biennial.

Propagation:

Reproduces by seed (achene) only.

Emergence:

Peak emergence has typically been October, with significant emergence also in April, May and August.

Range and habitat:

Most commonly found in the Golden horseshoe area of Ontario but has been documented in southern, central and eastern Ontario.

Competitiveness:

Considered highly competitive and significantly reduces crop harvesting efficiency.

Identification clues

Seedling

Cotyledons:

Orbicular to oblong.

Leaves

First leaves:

Green, deeply divided into 4 or 5 segments.

Mature leaves:

Green, finely divided, hairless and odourless. Plants will usually form a rosette.

Mature plant

Stem:

Green, hairless, but can be reddish/green at the base.

Flowers:

Daisy like flower head; yellow centered, tubular with white ray florets. Flowers in the summer months.

Fruit/seeds:

dark brown, 1–2 mm long, 0.5–1 mm wide.

Roots:

A dense fibrous root system that firmly anchors the plant to the ground.

Often mistaken for

I know it's not Stinking mayweed because Scentless chamomile lacks any odour when the leaf tissue is crushed, and the leaves are hairless while stinking mayweed has slightly hairy leaves.

I know it's not Pineappleweed because Scentless chamomile lacks any odour when the leaf tissue is crushed compared with a pineapple like odour of pineappleweed. Scentless chamomile has white florets on its flowering head, pineapple weed does not.

I know it's not Ox-eye daisy because the leaves are dramatically different with scentless chamomiles being finely divided compared to the broadly divided ox-eye daisy.