January 2021 EcoQuest: Seize the Cheese

Kickin' off the New Year with a new EcoQuest!

Join the January EcoQuest: Seize the Cheese.
Find and map as many cheeseweed plants (Malva parviflora) as possible.

An ambiguous leafy green plant, cheeseweed can be found all over metro Phoenix. Green and growing in January, this naturalized “weed” has both its uses and drawbacks.

Join the EcoQuest here: Seize the Cheese
See it on SEINet

Cheeseweed (Malva parviflora) is a somewhat low-growing forb that can form large, overtaking clumps, sometimes the size of small shrubs. It was documented in metro Phoenix in the early 1900s. The voucher below was created in 1940, in the Salt River Pima-Maricopa (Onk Akimel O’Odham and Xalychidom Piipaash) area. It is assumed to be introduced to North America from Europe in the early 1800s, possibly intended as an edible green.

The common name “cheeseweed” comes from the fruits resembling a tiny wheel of cheese (Garden Betty has some wonderful images here). No, they do not smell or taste like cheese, but these fruits are edible, along with the leaves. This plant has been eaten raw or cooked for ages in the Mediterranean Basin, often being used in ways similar to spinach. Medicinal uses have also been reported for cheeseweed. Pliny the Elder even wrote that “a spoonful of mallow would rid one of all diseases.” Caution needs to be taken, however, when harvesting and eating this plant, especially in urban areas. When growing in nitrogen rich soils, the leaves can accumulate high levels of nitrates, leading to nitrate poisoning. Always seek advice from a professional before using a plant for food or medicine.

Image of flowers by Leslie Landrum. Cheeseweed fruit image credit: Ohio State Weed Lab, The Ohio State University, Bugwood.org.

Ironically, cheeseweed can harm other crops. It can outcompete desirable crops and cause a decrease in yields. In addition, they can interfere with machines that are used for harvesting and can vector various viruses, including tomato spotted wilt, alfalfa mosaic, yellow leaf curl, and cotton leaf crumple. Once established, they are very difficult to remove due to their long taproot and seeds that can last for years in the soil. Since cheeseweed tends to grow close to farmland and pastures, it can be a considerable problem for farmers in the area.
In addition, cheeseweed can crowd out native plants and is considered invasive in certain regions. In our area, it has become naturalized (meaning it is a non-native that has been able to reproduce and maintain itself over time without human help). While not as tenacious as invasive grasses, it can be found in abundance in wilderness areas. Cheeseweed grows well in sites with disturbed soils, like vacant lots, alleys, and roadsides, which has landed it on ADOT’s list for maintaining right of ways. Near urban parks, playgrounds and sports fields, it can even be a trip hazard. Surprisingly, this plant has not been observed in abundance on iNaturalist.

Cheeseweed growing in the Superstition Wilderness area.

Fun Fact: Cheeseweed is in the mallow family (Malvaceae) and is related to the plant that marshmallow confections were originally made from (Althaea officinalis).

Cheeseweed is considered both an edible and medicinal plant, as well as a problematic weed. Data for these plants is lacking in metro Phoenix, with only a little over 100 observations.Observing and mapping cheeseweed in metro Phoenix can provide information about occurrences, population size and density, which has yet to be estimated. Using the observation map, we can possibly see areas where it could be beneficial to remove this plant. We can possibly see how it could be crowding out native species in certain areas, such as local parks. This observation data could also help farmers to prevent its spread and control disease.

Scientific Name: Malva parviflora
Common Names: Cheeseweed, common mallow
Spanish: Hierba de queso; malva de flor pequena
Pima: Tashmahak
Family: Malvaceae (Mallow Family)

Duration: Annual or biennial, sometimes stated as perennial
Nativity: Non-Native
Lifeform: Forb/Herb
General: Introduced annual trailing or ascending herb, slightly pubescent to glabrate
Leaves: Orbicular or reniform, 2-7 cm long, crenate, undulate, or 5-7 lobed
Flowers: Usually May- October, 1-4 in leaf axils, short-pedicellate, calyx 3-4 mm long, accrescent to 7-8 mm in fruit, petals lavender or white, 4-5 mm long
Fruits: Nearly glabrous, mericarps around 10, rugose or wrinkled dorsally and winged at the angle between the dorsal and lateral walls
Ecology: Found on roadsides and in fields, disturbed ground and urban habitats from 1,000-7,000 ft (305-2134 m); flowers most of the year
Distribution: Native to the Mediterranean region, widespread as a weed in North America, but only reported once from the Chicago Region in a railroad yard. Can be found all over metro Phoenix, including natural areas
Ethnobotany: Decoction of leaves or roots used as a rinse for dandruff & to soften the hair after the hair wash. Infusion of leaves, soft stems and flowers used as poultice on swellings. Also used as a tea.
Notes: Malva parviflora is most similar to M. rotundifolia, but in that species the mericarps are not winged, its flower and fruit stalks are longer (at least 1 cm), and it tends to be a more low spreading plant. Also very similar is M. neglecta, but its flowers and fruit have much longer stalks, the mericarps are not wrinkled or pitted but are densely covered with short soft hairs, and the petals are obviously longer than the sepals.

Anywhere within the project boundary. Can be found largely in sites with disturbed soils, vacant lots, roadsides, alleys, urban parks, pastures and fields. Observations made anywhere there is not currently a group of observations are the most helpful!

SEINet: https://swbiodiversity.org/seinet/taxa/index.php?taxon=malva+parviflora&formsubmit=Search+Terms
Voucher: https://swbiodiversity.org/imglib/h_seinet/seinet/DES/DES00031/DES00031723.jpg
Native American Ethnobotany Database
Northern Arizona Invasive Plants
University of California Agriculture & Natural Resources
Plants for a Future
University of Arizona: Arizona Agriculture

EcoQuests are month-long challenges that are part of the larger Metro Phoenix EcoFlora project.
You can learn more and join the Metro Phoenix EcoFlora here:

Sign up for the newsletter at ecofloraphx@dbg.org.
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PLEASE observe COVID-19 guidelines/recommendations.
This a great opportunity to get outdoors close to home as we all navigate the complications of COVID-19. However, it is imperative that you follow the guidelines/recommendations of your local governments and institutions (wear a mask, practice physical distancing and wash your hands). Do what’s best for you and your community.

Arizona Office of Tourism: Responsible Recreation in AZ

Please do not observe indoor houseplants or pets.
For your own safety and the protection of plants and wildlife, do not trespass when making observations. Please follow all posted rules and guidelines in parks/preserves and do not enter private property.
Do not remove or move natural materials (plants, animals, rocks).
Respect wildlife (do not touch, feed, or disturb animals and keep a safe distance).

Publicado por jenydavis jenydavis, 31 de diciembre de 2020


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