There are lots of state laws in the US concerning wild flowers and restrictions against picking them along the public highways. For instance, in Texas where I grew up, you can get arrested picking blue bonnets (state flower) along a country road, and I'm sure that applies to Indian paint brush and all the rest. But, I don't know if that applies to private property - knowing Texas, where property rights are king, I kind of doubt it. I have no idea about New york, where I live now.