Terri, the farm you described sounds stunning! I have happened upon wooded areas while hiking that were carpeted with them- truly breathtaking. I started with just 2 plants 7 years ago. Increase was slow at first, but in the 4th year I started finding seedlings and since then increase has been steady but confined. I believe the area I have them growing is dryer than they would prefer.
I've considered harvesting the seed, but have never been able to get more than a few. They hide well and are hard for me to see.
