While it can be tricky to identify some Malacothamnus due to lots of overlapping morphological characters in the keys, most don't overlap geographically. If you are in an area where only one taxon is known, you can usually be pretty sure of the ID based on that, assuming that it is a wild plant and wasn't introduced in a restoration project. If only two or three taxa grow in that area, that also helps narrow down the possibilities. To address this, I've uploaded rough ranges of Malacothamnus taxa to iNaturalist. These will be updated with improved maps as this project progresses.

The image above is the range map of M. fremontii, which you can view an interactive version of here. The pink is the range I have uploaded, the green are counties where there are iNaturalist observations, and the orange is where someone put it on a list for a county where it may or may not actually occur. Malacothamnus orbiculatus has often been confused with M. fremontii and sometimes lumped into it. Compare its range here or on the map below and you'll see there is only a small area where they overlap and likely intergrade/hybridize (near the "S" in "Sequoia National Forest").

iNaturalist observation maps can get pretty messy for rare plants as iNaturalist obscures the coordinates. This is a very good thing for some species that really need that protection but a one-size-fits-all approach to the 1000+ rare plant species in California is more of an impediment to conservation for most (see views on that debate here). A rough range map doesn't give exact locations but does give you a better idea of where something may occur. See the range map of M. palmeri here and below. Once again, the two larger pink polygons is the known range. All the smaller circles of a similar color are obscured iNaturalist observations. Not a single one is in the known range of the species and most would have you believe this shrub is an ocean dwelling organism.

Many people have shared their coordinates with this project, which has been useful in making these rough range maps. This data will be used in creating better maps for the new treatment of the full genus I'm working on as well as for conservation assessments. There are many people out there that have observations with obscured coordinates that have not shared them with this project. I will tag all these people below. If you are one of them and would like to contribute plant locations to this project, see the instructions here to share your coordinates with the project. Thanks to all who have and will contribute!

Update Feb. 2023 - I have removed tags to people that had obscured coordinates as I'm mostly done with this research and many of the Malacothamnus taxa that were originally obscured on iNaturalist are no longer. Thanks to all who have helped with this project!