Growing Itoh Peonies – Yes, You Can Do It!

Growing Itoh Peonies – Yes, You Can Do It!

Zone 3-8          Full Sun to Part Sun ( In the afternoon)         Herbaceous perennial

Mature sizes vary with cultivar but most are 60- 90 cm tall with a 1.2 m spread. 

In 1948, Dr.Toichi Itoh of Japan was successful in hybridizing the common peony with tree peonies. Just a few of his seeds germinated and it would take another ten years for those seedlings to grow to full size and produce huge, buttery yellow flowers. Unfortunately Dr. Itoh died in 1956 and his family gave an American botanist, Louis Smirnow permission to bring four plants to the U.S.A. where he patented and renamed them. Peony breeders continue to produce new hybrids in white, yellow, pink, coral and red.

Itoh Peonies (Paeonia cvs.) are considered the royal family of the peony world.  And if you ever see a mature Itoh blooming, you will know why. These peonies have everything going for them – huge, long lasting, mildly fragrant blooms (20-23 cm across) and mounding foliage with an interesting texture that can stand on its own in the landscape. Depending on cultivar, they produce single, semi-double or double blooms from early summer into the fall. They must be deadheaded to encourage more blooms. Classified as a herbaceous perennial, they die back to the ground in late fall and regrow in spring from the ground up.

Itoh peonies make beautiful cut flowers. Cut the stems in early morning or evening when the blooms are almost fully open. Remove any foliage on the stems that will be below water. Submerge the ends in the water right away after cutting.

Itohs are slow to mature but can be long lived – some lasting fifty years or more!  There is no need to provide a cage for support as they have strong stems and branches

Location

Peonies do well in full sun, in a sheltered location. They grow best as a perennial border plant in a location that does not compete with shrub and tree roots. If you are planting more than one as a mass planting, do plant them 1.2 m apart (on centre).  It is important to have good air flow between the plants.

Soil: Peonies love a rich, slightly acid to neutral soil, preferably amended with compost. The most important requirement is to provide good drainage.  The soil should not be overly moisture retentive as the tubers will rot in very wet conditions.

Planting

When working with peonies, do clean and sterilize all tools before and after use and wear gloves. This helps to avoid spreading fungal and bacterial diseases. 

Most one gallon pot nursery Itoh peonies found in garden centres are at least two years old. It is important to get the roots established in the first year after planting before expecting flowers. These plants can be slow to mature so you may not get flowers for a couple of years after you plant.

Do plant your Itoh right away after purchase. Space them 1.2 m away (on centre) from other peonies and plants. If the crown of the plant is a good 5 cm below the pots soil line, make sure it is at the same level when planting in the ground. The crown needs to be two inches below the soil line for the plant to bloom properly.

Water the newly planted Itoh with a root stimulant mixed with water. Always water at ground level to avoid fungal or bacterial diseases. Do not fertilize your newly planted peony until the following spring.

Fertilizer

Fertilize in early spring and summer with a balanced 10-10-10 water- soluble flowering plant fertilizer and a lower nitrogen fertilizer in fall – 5-10-10. You do not want to promote new growth going into late fall.

Propagation

Itoh peonies are sterile and do not produce viable seed.  Propagation is by division in early spring before new growth starts. Like the common peony, Itoh peonies do not like to be disturbed. They do not need to be divided and can be left in the ground where planted. If you choose to divide the root system do this when the plant is at least four years after planting.

Itoh peonies have a very strong, large root system. You will need a sharp spade to dig up the entire root ball leaving some soil around the perimeter.   Thoroughly rinse off the root ball so you can see it clearly. You may need a saw to cut through the crown, dividing the root ball into pieces. Each piece should have one strong root and 3-5 pink eyes exposed at the top of the crown.

Plant ASAP in new locations with the “eyes” 2 inches below the soil. Do not store the roots after division. I would mulch the new transplants the first fall when cleaning up for the winter. Compost makes a good mulch but spread no more than an inch around the drip line of the plant.  Never cover the crown. 

General Fall Care

Keep in mind that Itoh peonies that grow in zone 3 need a period of cold to promote blooming the following spring and summer.

Keep all areas clean of fallen leaves during the summer and fall.  This helps prevent fungal and bacterial diseases. 

Make sure the plants are regularly watered in the weeks leading up to a hard frost.

Itoh peony fall leaf colors vary with each variety – most turning reds, purples and oranges. The colors will vary year to year, depending on the fall climate in our area.

Once the foliage has died back in fall, cut the entire plant back to 4-6 inches from soil level.  Do not clip off the crown growth buds.  If the old foliage is diseased, do not compost.

Pests , Diseases and Problems

Itoh peonies are somewhat resistant to various types of peony blight. They can be susceptible to powdery mildew and botrytis.

Insect Pests - Japanese beetles

Ants will be attracted to the buds and flowers. You do not need ants to open the blooms – They are just interested in the sweet nectar. They will not eat the plant.

Failure to bloom – planted too deep. You can gently lift them with a spade but do allow for a good portion of earth around the roots. Slide in some extra soil under the lifted root ball and lightly water with a weak root stimulant solution.   

Leaf splotches and spots – Possibly a fungal infection. If a lot of the leaves are affected it is best to destroy the plant.  Do not compost.

A Few Zone 3 Itoh Peony Cultivars

Bartzella – Large, bright yellow, double blossoms with a slight crimson stain at centre.  (Z2-3)

Hilary – Bicolor -yellow-pink (coral).  Fragrant.  Semi-double flowers. A late spring bloomer. Pink petals that age to cream with a contrasting maroon red eye and yellow stamens.  (Z3)

Callie’s Memory – Huge fragrant flowers in late spring. Semi-Double- 7 inch blooms are yellow cream in color, edged with a deeper russet with maroon flares and a picotee edge.       ( Z2-3)

Enduring Rainbow – An early season Itoh. Flowers show a palette of yellow, peach, pink, cream and rose.  Single to semi-double blooms are borne on 90 cm stems and rarely need staking.  (Z3)

Scarlet Heaven – Single scarlet petals with a multitude of central yellow stamens.   Deer and rabbit resistant.  Highly fragrant.   (Z3-8)

 All of the above attract pollinators!