On a recent trip to am unnamed box store for some spring renovation supplies, we were surprised to see intersectional peonies offered along with the standard spring selection of dahlia tubers and gladiolas bulbs. It was only a few years ago that intersectional peonies, hybrids between tree and herbaceous peonies, were so rare that they could only be found at specialty nurseries such as ourselves. Today, thanks to increased importation of Dutch grown intersectional peonies, they are found more frequently at less specialized nurseries and garden centers. However, as many of you know, not all peonies are equal.
Archive for the ‘Tree Peony Care and Reference’ Category
Among the three types of peonies- tree, herbaceous and intersectional, there are a variety of growth habits. Along with sun requirements, the mature form of a given variety is an important consideration when planning to add a peony to your garden.
Tree peonies, like other woody perennials, are comprised of a thicket of stems which emerge out of the ground from the root system. Tree peony growth habits are categorized according to the angle at which the branches grow relative to the ground.
Upright form tree peonies
Upright form tree peonies tend to be vigorous varieties with comparatively long annual growth. Stems and branches grow upwards, at a narrow angle to the ground. The example shown here ( Sichuan Peach Blossom) is about 6 ft. tall and 6 ft. wide, and has been pruned of lower leaves and small branches to allow an uncluttered, open form of the shrub.
Tree peonies with this growth habit include: most cultivars in the Chinese rockii and Japanese groups, some Central Plains Chinese and hybrid tree peonies. Final mature height will vary between 4.5 to 7 ft., depending on the cultivar. In our plant descriptions, we do include the mature height of our cultivars.
Landscape uses: Tree peonies with upright growth habits make excellent display plants. Do not be intimidated by the height, keep in mind that tree peonies are slow growing plants which take 10-15 years to reach their mature size. Vigorous cultivars can also be kept smaller with yearly pruning. Grow in USDA zones 4-9, with at least 5-6 hours of sunlight.
Spreading form tree peonies
The branches of the spreading form tree peonies expand out diagonally to the ground, so that the plant width is much greater than the height. This type seems slower growing than upright habit tree peonies. At maturity, tree peonies with spreading growth habit measure between 2.5-3 ft. tall and 3-5 ft. wide.
Tree peonies with this growth habit include: Some Central Plains cultivar group of Chinese tree peonies (includes many of the historic Chinese varieties), some hybrid tree peonies.
Landscape placement: Mixed perennial border or foundation planting. Also very attractive planted on a raised terrace which allows for easy viewing of downward facing flowers. Ideal for smaller gardens. Grow in USDA zones 4-9, with at least 5-6 hours of sunlight.
Semi-spreading form tree peonies
The semi-spreading growth habit is characterized as being an intermediate between the upright and the spreading types. Typically dimensions at maturity are between 3-4 ft. tall and 3-5 ft. wide.
Tree peonies with this growth habit include: All cultivar groups of tree peonies have some varieties which can be classified as having a semi-spreading growth habit. The majority of hybrid tree peonies are semi-spreading.
Landscape placement: Very versatile, can be used as either a focal specimen plant or as part of a more diverse garden setting in a mixed shrub and perennial border. Grows in USDA zones 4-9, requires 5-6 hours of sun to bloom well. Tree peonies will grow in full sun, but the flowers fade more quickly. Morning sun, afternoon shade is ideal.
Species Herbaceous Peonies
There are approximately 25 species of herbaceous peonies which can be found in the wild over a wide swath of Eurasia, from the Mediterranean to Japan. They are lower growing plants, between 1 to 2.5 ft. tall. Some species, like P. japonica, remain small plants which will not exceed more than 1.5 ft. wide. Others, like P. macrophylla will become large clumps with time, up to 3 ft. wide.
Landscape use: Some species, like P. japonica are ideal for the shady margin between the deciduous forest and the garden. Other species require full sun. All add delicate color to the early spring garden. Be aware that many species peonies will have their foliage die back in the heat of summer.
Lactiflora type Herbaceous Peonies
Cultivated varieties of P. lactiflora account for the vast majority of herbaceous peonies in commerce. This species, which is native to China, forms a tall, upright bush, generally 3.5 ft. tall and wide. Some are single form flowers, while others are fully double form. Some cultivars are weak stemmed and require support, while others have markedly stronger stems. We have test grown more than 150 herbaceous peony cultivars in 25 years and have discarded many because their stems are too weak. We select out the better peonies to propagate and sell, those with vigor and good stems, fragrance, unique form and color.
Landscape uses: Devoted beds or borders. A widely adaptable garden favorite for generations, used in mixed perennial borders with at least six hours of sunlight, to a full day of sun. Will grow in USDA zones 3-8. Some herbaceous peonies will grow and bloom in zone 9, but must be planted just below the soil surface. Difficult to establish in zone 9 due to dryness and lack of winter dormancy.
Hybrid Herbaceous Peonies
Hybrid herbaceous peonies are the result of crosses between different peony species. Sizes within this broad group are quite variable, between 2.5-4.5’ tall and 2.5-3.5’ wide. Many of these hybrids were first created in America, in the mid-t0-late 20th century.
Landscape uses: The wide range of flowering times and diverse plant habit make these widely adaptable landscape plants. Many of the new hybrids have been selected with an eye for stunning flowers as well as good stem strength. Used in mixed perennial borders with at least six hours of sunlight, to a full day of sun. Will grow in USDA zones 3-8. Some herbaceous peonies will grow and bloom in zone 9, but must be planted just below the soil surface. Difficult to establish in zone 9 due to dryness and lack of winter dormancy.
Intersectional or ‘itoh’ hybrid peonies
These are hybrids between tree and herbaceous peonies. Well formed bushes grow to 3-4 ft. tall and wide.
Landscape uses: Well suited for mixed perennial borders or foundation plantings. The plants require 6 hours or more of sunlight. The foliage is attractive from early spring to the hard frost. The foliage will die back in late autumn and is cut down, to re-emerge in the spring. Clumps get larger over time. For USDA zones 4-9.
Peonies bloom in a wide range of forms, from simple, elegant singles to massive doubles with more than 300 petals. In China, where the peony has been cultivated for over 2000 years, growers have developed a rather complex system for classifying tree and herbaceous peony blossom shapes. Peony culture has a much shorter history in Europe and the United States. The system used by American growers to classify peony flower shapes is less specific than that used in China. At Cricket Hill Garden, we try to use the Chinese system for classification of flower forms. We feel that it is a better tool for recording the nuances between different cultivars. While a shorthand of single, semi-double and double is perfectly adequate for understanding the basic difference in peony flower forms, the Chinese system is for connoisseur gardeners with a well developed appreciation for the subtleties of the nature of the flowers.
Its somewhat akin to drinking tea or wine; while a black Lipton’s teabag is fine, and Mondavi is drinkable, others find joy in the perfect blend of a select plantation tea or discovering a new 90 point expert’s vintage.
Historically in China the preference amongst gardeners seems to have been for extravagant double blossoms. We have had experience growing these over the past 25 years and some of them are very difficult to bloom in the true form. The soil and nutrients have to be in balance, a double form flower will not perform well in less than optimal soil.
Over the last several decades, Chinese peony breeders have made many newer introductions of flowers with lighter, more open forms. The vast majority of Japanese peonies are single or semi-double. American growers have largely adopted the lighter form preference, dismissing large double blossoms as “ungainly.” As a result most hybrid tree peonies selected by America breeders for propagation are single or semi-double form.
American gardeners, however have a continued devotion to large flowered double herbaceous peonies. Despite their weak stems, the big ‘poufy’ peony is still a favorite. What we have tried to do in our trials is select the best growing habits of the hundreds of peonies we have tried. When we recommend a tree or herbaceous peony, it is because we know it performs well, blooms easily and will have more than adequate stem strength. That is why you see a very discriminating ‘edit’ of our peony offerings, we want the best performers as well as the most stunning forms and colors.
The flower forms on the chart and the examples that follow show some of the best cultivars in each category.
Note the definitions of the forms as well as examples of peonies which bloom in the given form.
Single: 1-3 layers of petals that are large, wide and flat. Stamens and pistils are exposed. These flowers are normally fertile.
Lotus (semi-double): Large and close fitting petals in 4-5 slightly overlapping layers forming the shape of a lotus flower. Both stamens and pistils are exposed.
Chrysanthemum (semi-double): Counting 6 layers of petals which gradually decrease in size towards the center. Stamens can be normal, or somewhat petaloid (where the stamens become petals). Pistils are normal.
Rose (semi-double): Counting 6 layers of petals, which are usually larger than the chrysanthemum form. Petals are larger on the outside than on the inside. Stamens and pistils are somewhat or mostly petaloid.
Anemone (double): 2-3 outer layers of wide and straight petals. Stamens are completely petaloid and have become small narrow petals. Pistils are either normal or reduced. Under the American system of classification, this form is known as “Japanese.”
Hundred Proliferate (double): Many- layered double, having the appearance of two merged and overlapping flowers. This is a common form, with many lactiflora type herbaceous peonies falling into this category.
Golden Circle (double): 2-3 outer layers of large petals. Most of the stamens are petaloid, but a ring of normal stamens remains and has the appearance of a golden circle between the narrow interior petals and the wide outer petals.
This is a rather uncommon form, though many of the more complex double flowers will bloom in this form when young or when not adequately fertilized.
Thousand Petal Crown (double): Wide and expansive outer petals. Stamens are completely petaloid and usually have the appearance of becoming larger from the exterior to the interior of the flower. The center of the flower is raised.
Historically, this was by far the most popular flower form in China. Many, though not all, of the cultivars which bloom in this form have flowers which are so large and heavy that they are side-facing, or down-facing. This does not mean they are all hidden flowers, they bloom from the side view rather than on top of the plant.
Hydrangea Globular (double): All stamens are completely petaloid with shapes and sizes similar to those of normal petals. Pistils are petaloid or reduced. These flowers are said to resemble hydrangea blossoms are well as xiuqiu, embroidered silk balls which are a traditional handicraft in parts of China.
This is a rarely encountered form. Cultivars which bloom in this shape require optimal growing conditions to do so because the flowers are so large.
There are some peony shapes which do not fit neatly into the above categories. An example is the “lion’s mane” form of tree peony blossom which was very popular in Japan in the 19th century. These flowers are typically semi-double and ruffled. These shaggy flowers are not as popular today and rarely seen in commerce.
Peonies which do not have access to adequate nutrition will not bloom up to their potential. Flowers on poorly fertilized plants will be smaller and simpler than their true form.
Peonies show alternate shapes and will often not bloom in their mature form when young. This is especially true of the more complex forms of tree peonies. The mature age for a tree peony is usually considered to be about ten years old.
Many of the full flower forms we offer now will bloom well by 5-6 years of age. We have discarded hundreds of peonies as too slow to bloom or too difficult to grow over the past 25 years. What we offer in 2014 is a result of the many years of trial growing here in Connecticut.
As our herbaceous peonies enter their grand finale for 2013, we have already begun to plan our fall peony planting at Cricket Hill Garden. Peonies are very long-lived and relatively carefree provided that they are given a good start. Planting healthy stock is of course vital, but equally important is to amend the peony planting area so that the peony will thrive there. Basically, this entails adjusting the soil’s pH to the proper level and adding adequate organic material to deficient soils so that the peony will be provided with long-term nourishment. A little work now will pay you back with years of beautiful flowers. See our youtube video on this preparing a new peony planting area.
The following is a deluxe method for amending unimproved, poor native soil
if you are creating a new planting area.
We add 2 lbs each of the following soil-building amendments to our planting site sized 3′ x3′:
- Azomite– (long term minerals and trace minerals)
- Hi-Cal (Calcitic) Lime- For calcium, this also raises the pH of the soil, 6.5-7.0 is ideal for peony growing.
- Colloidal Phosphate- For short-term calcium boost and slow-release phosphorus, very important for bloom production.
- Greensand- For improving soil texture and adding potassium.
We add 1 lb. each of the amendments listed below for building high levels of humus:
- Alfalfa meal
- Blood meal
- Bone char
- These amendments can be found through suppliers like Espoma and Dr. Earth which package for the home gardener, sold online or locally at well stocked garden centers.
Rather than rotor-till a new planting area, we like to smother the grass and unwanted plants. By not disturbing the soil, we leave the complex web of beneficial bacteria and fungi intact.
Allow the soil amendments, compost and mulch to sit over the next few months. In the fall, when you are ready to plant, pull back the mulch and compost from the center of the pile and plant your peony there. All of the good compost and mulch will nourish the peony and get it off to a great start.
If your garden area has better soil and has been worked before, a simpler method which will yield good results would be to add 1- 2 lbs Azomite and one wheelbarrow load of compost to the future planting area sized 3′ x 3′. If you know your soil is acidic, add 1-2 lbs. of ground limestone. Allow this to sit and ‘stew’ over the summer and in early fall your soil will be ready for planting.
Spring has arrived in most of the continental United States and peonies throughout the land are starting to put out their new growth for the season. We are often asked how to distinguish between new tree peony shoots and advantageous herbaceous graft root suckers. We hope that the pictures below might help to elucidate the difference. A degree of horticultural eye is required, especially when growth is first emerging, so if you are unsure, wait until the new growth has progressed to a point where you can distinguished between the different leaf types of tree and herbaceous peonies before removing any growth.
At Cricket Hill Garden, about half of our tree peonies are propagated by root division while the other half are propagated by grafting onto herbaceous peony rootstock. Some grafted tree peonies, if not planted to a proper depth, are prone to have their herbaceous under-stock sprout, or in horticultural terms, sucker.
If the new growth around your tree peony looks like that in the above photo, you should remove it. See our past blog post, on how to do this. Before you chop out any new growth, be sure that what you are seeing is not just the tree peony sending up new stems from its own root system, as shown in the picture below.
If you are unsure if the new shoots which you are seeing are tree or herbaceous peony shoots, its best to wait until the first leaves appear. Tree peony leaves will be dissected, while herbaceous peony leaves are more ovate.
If you have any questions, about this or any other peony related topic, please email us at email@example.com.
Early spring is the best time to prune a mature tree peony. The window to do this after the buds have begun to swell, and before new growth has commenced.
We have long known that many of our customers have had success growing peonies in the warmer parts of USDA zone 8 and 9. However due to the extreme and unprecedented conditions seen in some areas of these zones in the last two years, we recently contacted some very experienced growers in these parts of the country for some concrete advice on getting peonies to thrive there.
If you grow any types of peonies in zone 8 or 9 and would like to add to our growing advice, we would love to hear from you!
Growing Peonies in Dallas, TX (USDA zone 8)
Typical bloom time: Late February to early March for tree peonies. Herbaceous peonies begin to flower around April 1st.
Recommend types of peonies to grow: Growers have had success with all types of peonies, tree, herbaceous and intersectional. (Intersectional peonies are also known as itoh hybrids.)
The last two brutal summers have had extreme weather conditions. In the 2011 drought and 2012’s unprecedented heat wave, all plants have suffered.
One gardener reported that over the last two summers, many plants in her well established gardens failed to survive the stress. These include hydrangeas, modern rose hybrids, and some tree peonies. Tree peonies which had thrived for 6-7 years in the ground died due to drought related stress. However, this very experienced gardener reported that her ‘Snow Lotus‘ tree peony has done exceptionally well despite the drought. In fact, she said that it is the only tree peony which she would unequivocally recommend for gardeners in her area. Her specimen is nearing 10 years old, is 4.5’ tall and produced 26 blossoms last year.
It makes sense that ‘Snow Lotus,’ which is a cultivated variety of the wild species Paeonia rockii is more drought and stress tolerant that other types of tree peonies which have been hybridized under more favorable growing conditions. The native range of P. rockii is northwestern China, particularly in Gansu province, a very arid region which averages just 12” of rain a year! This is less than half of the rainfall which Dallas, TX received in the drought of 2011.
Growers in hot, arid parts of the country interested in growing tree peonies are then recommended to consider the rockii or Gansu Chinese tree peonies. Some of our favorites include: Cup of Shining Night, Black Tornado, Blue Jade in Three Colors, Purple Butterfly in the Wind and Pink Lotus.
Herbaceous peonies do not pose any special challenges and are widely grown in this area.
Best planting time: Either November-December, or late January- February.
Site Selection: Its best to plant peonies in warmer climates so that they receive a little protection against very hot summer afternoon sun. As we recommend for all planting zones, morning sun and afternoon shade is ideal. If this is not possible, than plant peonies near a large shrub so that they are afforded a little protection from the very hot sun.
Watering: In spring and summer, at least two deep waterings a week with supplemental drinks in between as necessary. This is doubly important for newly planted peonies.
Pests and Diseases: Nothing significant.
Other tips: Remove any remaining tree peony leaves in the beginning of November. For herbaceous peonies, cut foliage to the ground at this time as well.
When planting herbaceous peonies make sure that the ‘eyes’ or buds are basically at the surface with only a very lite layer of soil or mulch covering them.
Peonies in Northern California (USDA zone 8b to 9)
Typical bloom time: The following detailed bloom sequence was observed over the course of a decade in Sebastopol, CA .
- P. tenuifolia and assocaited hybrids such as ‘Early Scout‘ bloom in late February to early March
- Chinese tree peonies in mid-March
- Japanese tree peonies and P. lutea in early April
- Interesectional peonies peak from May 1st-10th
- P. lactiflora type herbaceous peonies from mid-May to early June.
Recommend types of peonies to grow: Consult a detailed zone map, such as Sunset’s Magazine garden zone guide for more accurately determining your planting zone. This index is much more detailed than the USDA’s zones. For instance, both San Francisco and Sebastopol, CA are both classified as USDA zone 8. However, while tree and interesectional peonies do well in San Francisco without any special attention, herbaceous peonies are a challenge there. Just a little north, and still within the same USDA planting zone in Sebastopol. In addition to tree and intersectional peonies, the majority of herbaceous peonies are proven to grow very well, with the exception of some very late season varieties.
We have heard from a gardener who has good success growing the earlier blooming types of herbaceous peonies in San Francisco. Her trick is to empty a bag of ice on top of her dormant plants once a week in December and early January. This gives the plants the necessary chill time to bloom.
Best planting time: late November to early February.
Site Selection: Planting in a half-sun/half shade location is ideal. In sunnier locations, peony leaves will become scalded in the summer.
In the warmer areas of zone 9, work with micro-climates within your garden to find cooler planting areas. Planting in cold air pockets such as at the base of hills can extend the growing range.
Watering: In zone 8b one or two deep waterings per week in the summer as necessary. Take special care of newly planted peonies.
In the warmer parts of zone 9, late spring, summer and early autumn irrigation is required. This is best accomplished by hand or drip irrigation at approximately one gallon per plant every other day with good drainage. Mulching aids in decreasing evaporation loss.
Pests and Diseases: March rain can cause botrytis outbreaks. Based on the amount of rain, several treatments with either Actionovate or copper-sulfate may be necessary.
Gophers do not eat peony roots, however they will eat nearly every other root in the garden. Their tunnels can damage peony roots.
Other tips: Force dormancy on intersectional and herbaceous peonies by cutting them to the ground in November. Remove any remaining leaves for tree peonies at this time as well, be careful not to cut the woody stems, remove only the leaves and leaf stems. Trimming the leaves off mimics the deciduous leaf drop in colder areas and cycles the plant into producing new flower buds. Peonies must have a rest period without foliage.