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Arctotheca calendula

Arctotheca calendula is a plant in the sunflower family commonly known as capeweed, and it originates from South Africa.

Arctotheca calendula is naturalized in California, Spain, Portugal, Italy, Australia, and New Zealand, and considered a noxious weed in some of those places.

Arctotheca calendula is an annual rosette herb, which grows in rosettes and has sprawling stems that can spread across the ground quickly. They have a self-supporting growth form which allows them to achieve this vertical growth using their own supportive tissues. They have simple leaves and daisy-like flowers with small yellow petals. The plant can reproduce via seed dispersal.

Arctotheca calendula’s flora category is a vascular plant that is an Exotic.

Capeweed has the capacity to infest pasture and turf and can cause competition in economically important crops. It can also cause allergies and dermatitis in individuals who are sensitive and negatively affect stock production.

Description
Arctotheca calendula is a widespread annual herb. Capeweed is a short-lived, low-growing plant that has semi-upright flowering stems of up to 30cm tall. It's leaves are 5-25 cm long and have a width of 2-6 cm wide. Their seeds are 2-2.5 mm long and are densely covered in a fluffy pinkish or brownish colour wool.

Capeweed is an annual rosette herb, which grows in rosettes and has sprawling stems that spread across the ground quickly. They can spread up to 30cm long. The leaves are covered with woolly hairs. Capeweed leaves are lobed or deeply toothed. They can grow up to 25 centimetres tall. Capeweed has daisy-like flowers with small yellow petals. The flower heads are solitary and around 3.5 centimetres across, with small black disc and yellow rays. The plant reproduces via seed dispersal by people, wind and sand movement. Capeweed is a noxious weed and has invasive potential.

Distribution
Arctotheca calendula originated in South Africa. Arctotheca calendula is naturalized in California, Spain, Portugal, Italy, Australia, and New Zealand, and considered a noxious weed in some of those places. Arctotheca calendula prefers bank, clay, slope, track, cliff, dry gravel, margin, hill, open, pasture, paddocks, ridge, roadside, rock outcrop, sand, wasteland, shaded, and shrubland habitats. Capeweed prefers a good amount of sun and well-drained sandy soils. It is often the dominant plant in over-cultivated or overgrazed lands, bareground and along roadsides especially in poorer soil areas.

Life cycle
Capeweed has a medium seed bank life span and has up to 4330 seeds per plant at seeding time. Arctotheca calendula is an annual rosette herb. It produces abundant amounts of seed which are dispersed by wind, water, people and sand movement. The woolly seed which is usually spread by wind or water, germinates during the cooler months. The large rosettes of low-spreading levels develop. The plants then die off when the hot dry conditions take over. Capeweed generally flowers from August to October and December to April (spring to early summer). It fruits anytime from October to April.

Interactions
Capeweed is eaten by a number of predators including butterfly species such as Junonia villida (meadow argus), birds species such as Psephotus haematonotus (the red-rumped parrot), Chenonetta jubata (the maned duck or Australian wood duck), Cacatuidae (cockatoo), and insect species such as Nysius vinitor (Rutherglen bug). Capeweed is a higher fertility weed species as they thrive where soils are fertile and soil nitrogen is high. Under certain conditions capeweed can cause nitrite poisoning in livestock. This is most likely to occur in areas where capeweed is growing in high fertile soils. Capeweed is predominantly pollinated by butterflies.

Further information
Capeweed is a dicot (dicotyledon). This means that it has features such as a tap root and leave veins with net venation.

Capeweed is a noxious weed. Its robust flat growth allows it to choke out other plants species around it. In situations with grazing stock where capeweed has choked out other pasture plants and little alternative pasture is available this plant can cause nitrate poisoning. This weed can be controlled through the use of herbicides and other Integrated Pest Management (IPM) methods (chemical, physical, biological and cultural).

Chemical resistance
Glyphosate is a herbicide used to control capeweed in many countries. Glyphosate was first used in 1970 for agriculture and rural uses under the trade name Roundup. Glyphosate has become an essential weed controlling tool in conservation agriculture systems, replacing other weed control practices. However, there is recent confirmation of glyphosate resistance evolution in capeweed population globally. There is already resistance from the species with photosystem-I inhibiting herbicides (contact herbicides known as membrane disruptors). This shows the importance of integrated pest management practices. Capeweed is an annual herbaceous global weed that infests annual crops and pastures. Capeweed is economically damaging due to its aggressive competitive nature to compete with other plants for resources and can act as a host for numerous pests and diseases. Capeweed can be difficult to control as it has protracted germination (prolong seed germination) across a wide range of environmental conditions and is quick to establish at very high densities.

Use
Capeweed however can be a useful pasture species in certain dryer places such as Western Australia. This is due its success and capacity to set seed quickly and in large numbers even in moisture stress environments and its efficient seed dormancy mechanisms which is in balance with the environment of medium and low rainfall areas. It is largely a temperature controlled mechanism as capeweed dies during the summer, leaving seeds to regenerate after the dormancy period of cooler months.

Human health impacts
Capeweed has been connected with cases of compositae dermatitis. This is an allergic skin reaction and is usually caused through contact with the plant or pollen.