Scentless Chamomile

Scentless Chamomile (Tripleurospermum inodorum)

Report

Management Category

ID Characteristics

General: Scentless chamomile is an odourless, daisy-like flowering plant in the Asteraceae (sunflower) family that can act as an annual, biennial, or short-lived perennial.

Flowers: The flowers resemble daisies, with white petals and a yellow center. They are approximately 2-3 cm in diameter, and there is a single flower at the end of each branched stem.

Stem: The stems of mature plants range from 15 cm -1 m tall, and are smooth and branched. Scentless chamomile plants tend to be bushy when not subjected to competition, or after having been mowed.

Leaves: The leaves are finely divided into short, thread-like segments, resembling carrot tops. The “fern-like” appearance of the leaves distinguishes Scentless chamomile from oxeye daisy, a similar invasive species.

Seeds: Are rectangular, 2 mm long, dark brown, with three light brown ridges.

Similar Species

Invasive

Oxeye daisy (Leucanthemum vulgare): The leaves of oxeye daisy are broad and coarsely-toothed.

Oxeye daisy leaves

Pineapple weed (Matricaria discoidea): The leaves have a strong odour when crushed, differentiating it from scentless chamomile which has scentless foliage and flowers.

Pineapple weed (Brian Klinkenberg. E-Flora)

Exotic

True/German chamomile (Matricaria recutita): Has fragrant flowers and foliage.

German chamomile (Photo credit: Eleftherios Katsillis, iNaturalist)

Stinking mayweed (Anthemis cotula): All parts of the plant, when crushed, release a urine-smelling odour. It also has fine hair on the stem, below the flowers.

Stinking mayweed (photo credit: Anna Nikolenko, iNaturalist)

Corn chamomile (Anthemis arvenis): Its stems are hairy below the flower heads.

Corn chamomile (Photo credit: lassedumke, iNaturalist)

Habitat and Origin

Native to Europe, scentless chamomile was introduced to Canada in the 1930’s as both a garden ornamental and a seed contaminant.

This plant is commonly found at low to mid-elevation sites, along transportation corridors, fence lines, and other disturbed sites. Preferring high moisture content in soils, scentless chamomile can often be spotted near ponds, streams, and other areas prone to seasonal flooding.

How it Spreads

Scentless chamomile propagates by seed, of which a single plant can produce up to 1 million that can remain viable in the soil for up to 15 years. The seeds germinate under periodic flooding conditions and can even float in a water body for as long as twelve hours! Therefore, they are easily dispersed by water, as well as wind, crop seed, and animal feed.

Large infestations of scentless chamomile along transportation corridors can be primarily attributed to wind dispersal, and can serve as a major source of spread to adjacent agricultural areas and aquatic systems.

Impacts

Ecological:

Scentless chamomile crowds and competes with native vegetation, and forms monocultures near water bodies or riparian areas, on sites with heavy soils and high soil moisture, or in soils that are subjected to periodic flooding. Its versatility as an annual, biennial, or short-lived perennial causes it to be an extremely difficult invasive plant to control.

Economic:

Scentless chamomile forms dense stands and can negatively impact pastures, cultivated crops, and grain, seed, and hay fields by reducing crop yield.

Prevent the Spread

Scentless chamomile is found in the Sea to Sky region and its distribution is beyond landscape-level control. When scentless chamomile is present at high-priority locations and negatively impacting them, their control is considered a high priority.

Otherwise, the goal is to prevent it from spreading to new (uninfested) areas, and to control it where possible to limit its impact on biodiversity.

Learn to identify scentless chamomile: use the images presented in this profile page.

What to do if you spot it: You can report any scentless chamomile sighting by clicking here.

Play, Clean, Go. Remove plant material from any equipment, vehicles, or clothing used in areas with infestations. Wash equipment and vehicles at designated cleaning sites before leaving infested areas.

DO:

Regularly monitor properties for weed infestations.
Ensure soil and gravel is uncontaminated before transport
Frequent, shallow tilling in the late fall and early spring can destroy germinating seeds. Re-vegetate exposed soil with native species as soon as possible
Ensure plants (particularly flowering heads or root fragments) are bagged or covered to prevent spread during transport to designated disposal sites (e.g. landfill).

DO NOT:

Plant scentless chamomile in a garden, no matter how well-contained its enclosure may seem.
Move soil or gravel that has been contaminated with scentless chamomile.
Compost any plant material.
Unload, park, or store equipment or vehicles in infested areas.

Control

Mechanical

Mechanical control options, such as hand-pulling, are effective for small infestations of Scentless Chamomile.
In addition, mowing can reduce seed production. However, it should be done early and then again before the plant has flowered, with each successive mowing treatment lower than the previous one.
Burning infestations that have finished blooming, before they go to seed, can prevent them from spreading.

Chemical

Herbicide applications are most effective early in the season before flowering, but can be done throughout the season as long as plants are green and growing.
Effective herbicides include aminopyralid, metsulfuron methyl, dicamba, 2,4-D and picloram; however, picloram is not suitable for wet, coastal soils.
We recommend that any herbicide application is carried out by a person holding a valid BC Pesticide Application Certificate. Before selecting and applying herbicides, you must review and follow herbicide labels and application rates; municipal, regional, provincial and federal laws and regulations; species-specific treatment recommendations; and site-specific goals and objectives.

Biological

A seedhead weevil (Omaphalapion hookeri), stem-boring weevil (Microplantus endentulus) and adult gall midge (Rhopalomya tripleurospermi) have been released in northeastern BC.