Hey folks, jumping in here-zone 8a grower with a peony obsession that's cost me more therapy bills than actual blooms some years. Love the eye-count rule from above; it's spot on, though I once ignored it for a "bargain" division with just two puny eyes and ended up with a sad stick that mocked me all summer. Lesson learned.
On the container vs. direct planting debate, I've gone the pot route for marginal stock the last three seasons, using those fabric grow bags to air-prune and keep roots from circling. Planted 'em in a shaded spot with insulation wrap around the pots to mimic cooler soil-aimed for under 25°C root zone. Results? 90% transplant success to the field in fall, with way less shock than direct-burying desiccated roots (which I tried once and lost half to summer drought stress). Root balls were denser too, more fibrous architecture that held up better post-move. Downside: extra watering hassle, but if you're in a warm climate like mine, it's worth the babying to avoid that first-year flop.
For Itohs specifically, they're my go-to for low-chill hellholes-last year, I optimized establishment on a few Sarah Bernhardt hybrids (wait, no, that's herbaceous; think Bartzella and such) by holding them in pots through summer, and they pushed 4-6 stems by week 10 with zero chill faking. Herbaceous types? Still needy; my trials show they need at least 600 hours below 7°C for decent bud set, or you're lucky to get lanky growth and blooms delayed to year three. Tree peonies are another beast-slower to establish anyway, but I've had better luck with direct planting if roots are firm, as containers can overheat their thicker crowns.
Quantitative bit: Tracked soil temps at 5cm and 10cm depths last summer with cheap loggers (under $20 on Amazon). At 5cm, peaks hit 30°C+ by July, correlating to zero second-year buds on shallow-planted ones. Bumping to 8cm depth dropped that to 26°C max, and I got 70% bloom rate on year-two plants vs. 30% shallower. Paired with 450 chill hours here, that's my baseline for deciding if a division's worth the effort-if it's compromised, I trim aggressively (down to healthy tissue only), callus in vermiculite for 10-14 days at 15°C, then dip in a Trichoderma slurry. Saved about 55% of moldy rescues that way; anything with over 50% necrosis? Bin it, no regrets-sunk cost fallacy bites hard in gardening.
Anyone else logging GDD or forcing units for peonies? My setup's rudimentary, but it'd be gold for that decision tree idea. Spill your data!
