My guess is stinging nettle as well. When I was a boy scout in California, it was all over the place. We would make cordage with it at camps, and even boil it to eat it. Tastes like boiled spinach. It looks just like mint. Once my dad saw it and said "I wonder if that is mint?......never mind" as he screams. You can touch the leaf and not get stung also. I have seen it in Texas, and even here in Utah, but not to the extent I saw it in California.
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