Bush-mallow Challenge 3 - Arizona bush-mallows

If you are in Arizona or just south of the Arizona border, there are two possible bush-mallows to look for out there, maybe more. One of these is only known from collections taken in 1852 and the other is a more recent discovery with few known locations. As with all bush-mallows, relatively recent burn areas are the best place to look. Follow this link for an interactive fire map. See also my post here on what to focus on if you want to be able to ID a bush-mallow from photos.

The type specimens of Malvastrum thurberi which is currently a synonym of Malacothamnus fasciculatus are labelled as coming from Santa Cruz Valley, Sonora, Mexico and were collected in July 1852. Based on what I can find so far, this may mean the location was anywhere between Tuscon, Arizona and Santa Cruz, Mexico. All of the Arizona portion of this area was part of Mexico until the year following the collection.

Below is a scan of a type specimen (larger version here).


The second bush-mallow was collected at Spur Cross Ranch Conservation Area in Maricopa County in 2010 and called Malacothamnus fasciculatus. Based on the photos I've seen, these plants look most like southern populations of what is called Malacothamnus orbiculatus from Los Angeles and San Bernadino Counties in California. Gene Sturla has found additional plants in Tonto National Forest near Sycamore Creek which is also in Maricopa County. These were flowering in September. Below are photos of these plants taken by Gene.

(Update 4/1/19) I found one population. These are growing in a burned juniper woodland. This area burned 7 years ago and ~75% of the population is dead, so new populations are probably unlikely to be found in burn areas much over 10 years old. I would expect them potentially in any burned shrubland or woodland, but they do seem to be pretty rare in AZ. Lower elevation plants have been found flowering in late March and early April. These will likely flower in May. Go find more!
Observation here

Posted on August 13, 2017 05:38 PM by keirmorse keirmorse

Comments

Nice work Keir! We'll certainly keep an eye out for these. @stevejones

Posted by jaykeller over 6 years ago

I've seen one of these plants, but have yet to catch it in flower. It's on a DFLT property near Spur Cross Ranch in an area that floods regularly.

Posted by stevejones over 6 years ago

Will be on the lookout.

Posted by silversea_starsong over 6 years ago
Posted by keirmorse almost 5 years ago

I updated some of the info above based on the new observation. Go find more!

Posted by keirmorse almost 5 years ago

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