Older Bulletins from the American Peony Society (APS) can be read here. Except for a few missing issues all are available up through 2005. For current APS Bulletins and other benefits please consider membership in the APS.
Paeonia was an international newsletter for peony hybridizers and can be read here. It was published quarterly from April 1970 to spring 2002.
Interesting stuff, Koen!
I’m looking into these kind of things more and more also. Although not so much doing the scientific approach as you are.
Right before last planting (about 6 weeks ago), I dipped all our planters in two products of SoilTech: Root&Shoot (nutrient solution and humid and fulvic acid) and Optima Soil Humi B (humic acid with high Boron). I have followed advice on this from quite spectacular results in other cultures. When planting as late as we usually do on our rather stiff clay soil, the planters sure can use a little extra help settling. I hope to notice some results in spring.