stinknet
Oncosiphon piluliferum
About 4
Stinknet (Oncosiphon piluliferum) is a relatively recent and problematic arrival to Arizona. This plant is spreading rapidly in both urban and wild areas and can quickly dominate a landscape. This little winter annual (6-24 inches) has only recently been recognized as a prolific invasive weed in the Phoenix Metropolitan area and elsewhere in Arizona.
Stinknet, also called Globe Chamomile, is native to South Africa and was classed as an Arizona noxious weed in January 2020. The weed has spread from severe initial infestations in Northwest and North Phoenix into metropolitan Phoenix and now has a foothold in Tucson and Ajo.
Emergence starts in late November and plants can continue to germinate and emerge through the month of May in wet years. Leaves appear “carrot-like”, dark green and twice dissected and have a strong odor. Flowering starts in February and can continue through May. Flowers are bright yellow and ball shaped.
Plants grow in dense clusters and easily displace native vegetation. During growth the plants can cause severe allergic reactions, both dermal and respiratory. Infestations spread rapidly along roadways and open fields in residential areas. Dried dense patches are highly flammable.
Source: The Arizona Native Plant Society. (2020). Invasive plants. Retrieved from https://aznps.com/invasive-plants/
Description 5
Globe chamomile is a straggly, branching annual plant with a strong smell, growing up to 2 ft (60 cm) tall. The bipinnate or tripinnate leaves have a fleshy midrib which widens at the base. The globular flowers are borne in paniculate flower heads. There are no ray florets and the disc florets are yellow.
Ecology 5
Globe chamomile is native to South Africa and Lesotho. It is also found in the Australian states of Victoria and Western Australia.
In North America, globe chamomile grows from seed in November to January when it begins flowering and setting new seeds. With sufficient moisture, three generations can grow by April. Wind-borne seed transportation spreads the plant which takes root in sunny, disturbed soil in natural and cultivated areas. Plants can cause skin irritation or allergic reaction through contact with the plant or inhalation of its pollen.
A single plant can contain up to 4000 flower balls, each ball being made up of hundreds of flowers.
Invasiveness in the United States 5
Globe chamomile is considered invasive in the United States in California and Arizona. First seen in Los Angeles and San Diego in the early 1980s, it heavily infests the counties between those cities. It expanded its range to the Phoenix area in the first decade of the 2000s and can be found in Maricopa, Pinal, and Pima counties. Rapid spread in Maricopa County occurred due to above-average fall and winter precipitation in 2016, and 2018–2020. Heavy infestations occurred in northern parts of Phoenix and Scottsdale as well as to the south along the I-10 corridor towards Casa Grande. The first recorded growth in Tucson was in 2015.
The plant can be removed physically or killed with triclopyr; it is resistant to glyphosate-based herbicides.
The Arizona department of Agriculture considers it a "high priority pest for quarantine, control or mitigation if a significant threat to a crop, commodity, or habitat is known to exist." Other problems are its density which displaces native vegetation, high flammability of dried-out patches, and caustic smoke when burned.
Other names 5
Synonyms include Matricaria globifera because it was previously in the Matricaria genus, and Pentzia globifera, named for 18th century Swedish botanist Carolus Johannes Pentz.
The common name "stinknet" reflects the plant's strong odor.
Sources and Credits
- (c) 2003 Dean Wm. Taylor, some rights reserved (CC BY-NC-SA), http://calphotos.berkeley.edu/cgi/img_query?seq_num=125563&one=T
- (c) Felix Riegel, some rights reserved (CC BY-NC), uploaded by Felix Riegel
- (c) Nicola van Berkel, some rights reserved (CC BY-SA), uploaded by Nicola van Berkel
- (c) Jeny Davis, some rights reserved (CC BY-SA)
- (c) Wikipedia, some rights reserved (CC BY-SA), https://en.wikipedia.org/wiki/Oncosiphon_pilulifer
More Info
- iNat taxon page
- African Plants - a photo guide
- Atlas of Living Australia
- Biodiversity Heritage Library
- BOLD Systems BIN search
- Calflora
- CalPhotos
- eFloras.org
- Flora of North America (beta)
- Global Biodiversity Information Facility (GBIF)
- HOSTS - a Database of the World's Lepidopteran Hostplants
- IPNI (with links to POWO, WFO, and BHL)
- Jepson eFlora
- NatureServe Explorer 2.0
- SEINet Symbiota portals
- Tropicos
- USDA PLANTS database
- World Flora Online
