Also known as Intersectional Hybrid Peonies, these wonders are a cross between herbaceous garden peonies and tree peonies and feature the best of both.
Giant 6-9" blossoms (like the ones on tree peonies) open right after the garden peonies have faded. The growth habit is similar to garden peonies with attractive mounded foliage that dies back in the winter.
But do not cut Itoh peonies down the ground in the fall—next year’s buds need room to develop on the lower stems. Leave at least 6" of hardwood stems above the ground.
Named for Toichi Itoh, the Japanese hybridizer who supposedly made thousands of attempts to cross garden and tree peonies. He finally succeeded in 1948 but did not live to see his seedlings bloom. In the 1970s Toichi’s widow gave an American breeder permission to introduce Itoh peonies to the West, where hybridizers took up the intersectional torch.
Herbaceous Perennial Plants
When you receive your order, open the bags and check the stock. Roots and crowns should be firm and pliable. If they are slightly dry, add a little water or, if they are going to be potted up soon, wet the roots. Generally, a little surface mold is harmless and will not affect the plant’s future performance. If you cannot pot them up immediately, store them in a cool (35–40°) location for a short time.
Do not plant bare-root perennial plant crowns directly outdoors.
Pot up the rootstock using well-drained potting mix in a deep 6" pot or a 1-gallon container. Avoid coiling the roots in under-sized containers.
Grow newly potted perennials for a few weeks in a protected location in indirect light at 50–60°. Wet and/or cold conditions for an extended period may cause rotting.
Transplant outside once they show some top growth and the danger of frost has passed.
For more info:
About planting bare-root perennials.