Itoh peonies began as a hybridizer’s fantasy—which was to cross tree peonies with herbaceous peonies and thus to produce a new kind of plant that offers the best features of both parents.
For many years and in several countries, hybridizers had unsuccessfully pursued this goal. One difficulty was because the bloom times for the two types of peony are several weeks apart, making cross-fertilization difficult.
Also, although tree and herbaceous peonies are both members of the huge genus Paeonia, genetically they are actually not that closely related, contributing to the problem of creating a cross that would produce viable progeny.
Because of these genetic differences between tree and herbaceous peonies, modern taxonomists have actually assigned them to different ‘sections’ within the main Paeonia genus. And for this reason, these modern hybrids are sometimes called ‘Intersectional’ peonies.
A dream came true
Dr. Toichi Itoh, a Japanese botanist, toiling in the aftermath of the horrors of World War II, was the first person to successfully combine the pollen from a tree peony with the ovary of an herbaceous peony.
He was totally consumed with this monumental hybridization challenge and made thousands of attempts. Finally in 1948 his dream came true—a few of his seeds germinated. But it would take over a decade of patient oversight before those seedlings grew to full size and produced flowers. Then in 1956, eight years after his successful crosses, sadly Dr. Itoh passed away.
So it fell to his family to nurture those special plants, finally bringing them to flower in 1964. Eventually an American botanist, Louis Smirnow, got permission from Dr. Itoh’s widow to bring some plants to the USA where he patented four hybrid peonies—which he named Itoh hybrids— featuring huge buttery yellow flowers.