November 2020 EcoQuest: Broom Bloom

Join the November EcoQuest: Broom Bloom.
Find and map as many desert broom (Baccharis sarothroides) as possible. As a bonus, see if you can also find great purple hairstreak butterflies (Atlides halesus).

It’s that time of year, when desert broom starts to bloom, followed by the fuzzy fluff of seeds in the air. Often met with contempt and considered invasive, desert broom is a native plant with a variety of benefits.

Join the EcoQuest here:
See this plant on SEINet:

This EcoQuest is focused on desert broom (Baccharis sarothroides)
Desert broom often attracts attention for its abundance of fluffy seeds that float through the air around this time of year and coat the ground like a dusting of snow. The masses of floating fluff are often blamed for allergy problems, but the seeds do not actually carry pollen. There is also debate if desert broom pollen triggers allergies at all. Some sources state the pollen is “sticky” and relies on pollinators to transfer pollen. Others say the plant relies on wind pollination, with airborne pollen. This airborne pollen could trigger allergies while the plants are blooming, before the onset of seed fluff.
This plant is also known for its ability to multiply efficiently, thanks to the multitude of those floating seeds and is often labeled a “weed” or invasive. It is these characteristics that also make it beneficial. Desert broom is a pioneer plant, meaning it is one of the first plants to move in after a disturbance to the land. It can help stabilize soil, control erosion and help other plants get started. When established, their deep taproot helps break up hard soils and brings nutrients closer to the surface. It is extremely tolerant to heat, drought and poor soil. This plant can also be a great privacy hedge and wind screen.
Desert broom is a very important plant for pollinators, wildlife and people. The blooming time provides many pollinators with a much-needed nectar source in the fall, to survive into the next season or for migration fuel. A notable nectar seeker is the great purple hairstreak butterfly (Atlides halesus), which there are very few observations of in metro Phoenix. This plant attracts so many different species of insects that entomologists are said to look to desert broom to find what insects may be in the area. It isn’t just entomologists that are attracted to these insects, but birds and predatory insects like praying mantis as well. Birds and small mammals have also been reported to use this plant for nesting materials and eat the seeds. Many Indigenous peoples of the Southwest use desert broom for making infusions, teas, arrows and brooms.
To get the best of this plant without the seed fluff and unwanted volunteers (plants that grow on their own), you can plant male plants. The female plants produce the masses of airborne seeds. To control what plants may pop up in unwanted areas, pull plants (roots and all) while young before the taproot develops.

Fun Fact:
The specific epithet, “sarothoides,” means broom-like, referring to the branching structure that resembles a broom.

Desert broom is a beneficial plant for both people and wildlife. Data for these plants is lacking in metro Phoenix, especially in dense urban areas (Please see maps in the “Where to Observe” section).

Great Purple Hairstreak (Atlides halesus) observed by iNaturalist user @tomhorton.

Observing and mapping desert broom in metro Phoenix can provide information about occurrences, population size and density. This observation data can help explore possible wildlife and pollinator corridors. Bonus if you can find great purple hairstreak butterflies.

Scientific Name: (Baccharis sarothroides)
Common Names: Desert broom, rosin bush, broom baccharis
Spanish: Romerillo, hierba del pasmo, escoba amarga
Seri: Cascol caaco
O’oodham: Ṣu:ṣk Wakck
Family: Asteraceae (Sunflower Family)

Observers are encouraged to note the sex of the individual in the Annotation field, whether male (yellowish flowers without hairs) or female (whitish with abundant hairs). The Annotation field can be found in the right column of your observation on the iNaturalist website.

Duration: Perennial
Nativity: Native
Lifeform: Shrub
General: 3-12 feet tall and up to 6 feet wide, upright rounded broomlike habit, moderate to fast growth, evergreen, winter flowering, narrow, sharply angular, nearly leafless, green stems
Leaves: Alternate, sessile, few, and quickly deciduous; blades linear to linear-lanceolate, up to 2 cm long; larger leaves often minutely toothed, but most leaves are much smaller or reduced to scales
Flowers: Flower heads discoid and solitary on branch tips or arranged in dense panicles; male and female flowers on separate plants; pistillate florets white, and staminate flowers yellowish
Fruits: Achenes 10-ribbed, 2 mm long, with a pappus of bristles, 1 cm long, attached to the top
Ecology: Found in sandy-gravelly washes, watercourses, shallow drainages, flats, low hills, and roadsides, sometimes in saline soil from 1,000-5,500 ft (305-1676 m); flowers September-December
Distribution: s CA, s NV, AZ, s NM, sw TX; south to c MEX
Ethnobotany: Infusions used for coughs and stomach aches; stems were used to make arrows or tied together in bundles to make brooms
Uses: Erosion control, hedge and butterfly, bee and bird gardens

Anywhere within the project boundary, with a preference for dense urban areas where data is lacking. The dots on these maps are existing observations of desert broom. Observations made anywhere there is not currently a group of observations are the most helpful!

California Native Plant Society: Calscape
Southwest Desert Flora,%20Desertbroom.html
Spadefoot Nursery
Cochise County Master Gardeners
North American Butterfly Association
Felger, R. S. and M. B. Moser, 1985, People of the Desert and Sea. University of Arizona Press, Tucson, AZ

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
Let's be social @ecofloraphx

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, 28 de octubre de 2020


Publicado por tomhorton hace 4 meses (Marca)

Phenomenal! Thank you @tomhorton :)

Publicado por jenydavis hace 4 meses (Marca)

Wonderful essay, Jeny! As you note desert broom is a species some love to hate. The City of Scottsdale even lists it as an "invasive" species and encourages its removal. Yet it is a Sonoran desert native. It is adapted to disturbed soils in and along washes. But it also can be found in human-disturbed areas as along roadsides or on freshly-disturbed home sites. The fault, given Scottsdale's attitude towards it, is not in the plant, but in ourselves.

Yet the time spent standing among a population of it observing the myriad of flying insect species within it is time well spent. So many local and migratory pollinators utilize it this time of the year.

Given the sparse rainfall this summer I fear that finding plants in a reproductive state will be few and far between this year. But the thrill is the hunt.

As Jeny notes above, the species is dioecious, so I encourage observers to note under the Annotations column to the right the sex of the individual, whether male (yellowish flowers without hairs or female (whitish with abundant hairs).

Publicado por stevejones hace 4 meses (Marca)

@stevejones Thank you , Steve, wonderful and insightful information as always! I have updated with the annotation request. :) I was also wondering about the lack of rain, but have seen many in bud lately and am hopeful!

Publicado por jenydavis hace 4 meses (Marca)

I was at Seven Springs today (outside the metro area) and saw some in flower and with many honeybees visiting. Some of the females were already shedding seed. Most plants there were not in flower, though.

Publicado por stevejones hace 4 meses (Marca)

Agregar un comentario

Acceder o Crear una cuenta para agregar comentarios.