They shouldn't be in your climate (I'm assuming you are in western, not eastern Oregon). Roscoea likes cool summers, a rarity in most of the country but quite common in the northwest. In theory they can last forever if properly cared for.

Two possibilites come to mind about that advice. First, maybe he doesn't realize they go dormant in the winter and thinks they have died (unlikely but possible). Or the ground may be too wet during the dormancy period causing the rhizomes to rot (much more likely).

For a test you could try lifting some of the rhizomes in the winter and store them in a cool dry place (garage or shed). Then replant them in the spring and compare the survival rate to the ones that stayed in the ground.

I should say that although I am very familiar with the Oregon climate (my parent's live there), I have never tried to grow Roscoea there. So hopefully some NW gardeners can add to (or reject!) my advice.

-Kyle

We have Roscoea purpurea in the ground here on Vancouver Island. It is hardy and I would assume it would be hardy there too as it is further south where you live. Our neighbours have had theirs in the ground for many years and it has become a good sized patch. I have also had success storing them as Kyle suggests. I put mine in a shoe box which contains perlite.

Cheers,
MG

I have grown several species for many years and have never found them to be short lived they just keep getting bigger and better. They are quite late in emerging though, and every year I almost forget they are there.

My climate rarely gets above 30 in the summer and frosts are rare, but the climate is uniformly damp.