私有地でないところで花を摘むのは違法ではないですが、大量の花を摘むのは避けたほうが良いと思います。これは法律の問題というよりはマナーの問題ですね。少量であれば、許容の範囲内でと思います！
Although it is not illegal to pick flowers from non-private properties, I think it would be best to avoid picking up a large amount of flowers. This has nothing to do with legal problems but rather, is about issues of etiquette. If you pick a small amount of flowers, then I think it is within permissible boundaries!
