It grows wild all over the SE US and can withstand multi-year drought or regular floods though it does best in a situation where it gets regular rainfall. You may have some in your own yard used as a hedge plant. I have several large trees on my place. It spreads underground by suckers and will take over an area if you do nothing to contain it. It is very strong once it forms a thicket. I have driven across a yaupon thicket in a seismic buggy and been in a situation where none of the tires were touching the ground as I drove because I was crossing a thick tangle of yaupon that supported the vehicle.
Caffeine levels are lower than coffee beans (40-60 mg versus >150 mg I think). Yaupon does also have theobromines, vasodilators, that are supposed to help it prevent the caffeine crash.
I have some leaves dried and drink it make a tea occasionally when I want a boost but not a cup of coffee level boost. It tastes great and is easy to prepare at home.
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There are other sources of information about yaupon holly. It is proposed that the British naturalist who discovered Native Americans using it in their own ceremonies and drinking it casually decided to name it ilex vomitoria not because it was dangerous or poisonous to consume but because since it grew wild in the colonies, it could be a serious competitor to English tea so he used the name to make it less attractive.