Yerba Santa is actually several closely related annual plant species native to California and Oregon. In my personal experience, Yerba Santa can frequently be found along roadsides and in disturbed soils in the Sierra Nevadas, but CalScape suggests that they're mainly found in the mountains around SoCal and along the Pacific side of the Diablo range. The leaves are tough and leathery with a rich, dark green coloration on top and a fuzzy underside that looks much paler. The plant can be a little unpleasant to handle due to the sticky resin it secretes. The leaves are long and toothed, and grow off of stems that don't branch. I've never seen a single yerba Santa plant by itself, it almost always grows in small, dense clusters like you see in the picture. Yerba Santa also puts off clusters of trumpet-like purple-white flowers from the top that are used by native butterflies, but I haven't seen this in person.
Multiple sources report the medicinal use of Yerba Santa by both First Nations peoples (Miwuks and Yokuts to name a few) as well as Spanish settlers to treat a variety of remedies. As bitter as the plant is (also, tar is another foraging red flag for me; where there's tar, I usually expect that there's some pretty bioactive compounds like Nicotine, and that's a recipe for a bad time), I can't help but imagine that there's probably some compounds in it that might not be great to put in your body all the time, so I highly recommend doing your own research here. Also, a lot of the information about the supposed medicinal qualities seems really apocryphal and like it's just something that people repeat but never verify; I'd want to follow up with some people who have real experience with this plant before just going and chewing on it. For animals, Yerba Santa provides food for butterflies, native bees, and birds in the form of nectar and seeds, and has been documented as a forage of last resort by native blacktail deer when most other plants have already died or gone dormant. Additionally, Yerba Santa has been documented as being useful for stabilizing disturbed or scorched soils. There's a few weeds that could conceivably appear similar to Yerba Santa due to their habit of growing as a cluster of dense, non-branching stalks, but the tell I would suggest is the leaves. Most weeds that have similar growth habits won't have the same thick, robust, tar-covered leaves that Yerba Santa has, and won't have the trumpet-like flowers. The most serious lookalike, imo, is Oleander. Oleander is a woody shrub that gets much larger than Yerba Santa, but has similar-looking, rich dark-green, tarry leaves with trumpet-like flowers. OLEANDER IS VERY POISONOUS AND WILL KILL YOU IF CONSUMED. Oleander is not native, and is widely used as an ornamental throughout California. As a rule of thumb, if it's woody OR big OR looks like it's supposed to be there, it's Oleander.
Yerba Santa varies in hardiness. Like many California natives, it is wholly unafraid of summer sun; though most natives do fine with at least a little shade in the day, Yerba Santa is beyond such weakness. Some species of Yerba Santa can grow quite aggressively in disturbed soils, while others in the Santa Barbara region are seriously endangered. If you want to get your hands on this plant, I'd advise against harvesting Yerba Santa from the wilderness for several reasons:
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you could be harvesting an abandoned Oleander plant, and Oleander will kill you if consumed.
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you might accidentally be harvesting one of the endangered members of the species, which is not only unethical but likely illegal.
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Yerba Santa ain't no slouch, that plant is doing work where it is, holding the disturbed soil together and providing forage for wild animals through parts of the year when forage is scarce. You're hurting a lot of things that depend on that plant by taking it out of the ecology.
Instead, I'd strongly recommend getting some seeds from a reputable source and trying to grow some from seed.