I purchased a bulb of Lilium duchartrei and have looked up the hardiness zone info and there are discrepancies. It's one of the species I have wanted to grow for a long time. In zone 5a here, it would be easier to plant in my alkaline soil right into the ground, but also wanted to at least try not to lose it right away. I have read hardiness from zone 4 to zone 6.

Experiences with this species would be much appreciated. Thank you!

I have grown L. duchartrei for 15 years. Back then I was a solid zone 4a (now 4b) and with the soil freezing far deeper than in z4 states to the east. The first 5 years or so, I only had black heavy clay to plant in, with of a pH of 7.5 (guessing). Bulbs (2) were not blooming size and they increases slowly as I only had a full sun area at the time and they died back by mid summer.

First bloom the 3rd and 4th year at about 18 inches. One clone has since perished, and the other now grows in a raised bed of 1:2 sand and compost where it gets part shade and does better, growing 2.5-3ft (pH ~6.8). Is it because of the pH, soil composition or shade? Don't know. At any rate, I am now pretty sure that these Chen Yi clones are of less vigorous stock than what is available on the market now.
Although mine seem happy, they are quite pitiful in comparison to what Rimmer grows.

Thank you for your growing experience and correspondence on this, Rick. I appreciate your knowledge and perspective.