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Paeonia Culture
on this page: Herbaceous| Intersectional  | Woody

also see:  About Herbaceous Peonies
| About Woody Peonies | About Intersectional Peonies | About Peonies
Herbaceous Catalog  | Intersectional Catalog  |  Woody Catalog


Herbaceous Peony Culture

Herbaceous Peonies are one of the most easily grown hardy perennials available today.  Long lived and durable, a peony can live easily as long as 100+ years.  Most peonies in this group are of the 'lactiflora' species, in other words they are selectively bred plants originating from the species P. lactiflora, which originates in China.  Other species have been used with lactifloras to create hybrid herbaceous peonies.  The hybrids are often more upright plants with larger, more vibrantly colored flowers.  Both lactifloras and the hybrids are grown in the same way, have similar plant habits and needs.

Site selection is the most important factor in successfully growing any peony.   Pick a place to plant the peony in which it will not need to be disturbed for a number of years and receives at least 6 hours of light and preferably full sun.  Planting the peony too close to trees and large shrubs should be avoided since their roots will compete for water and nutrients.  Herbaceous Peonies, like all peonies,  prefer good garden soil that is well drained and has good amounts of organic matter.  They can be grown in clay soils, and do quite well,  provided it drains well.  

Peonies do best when planted in the fall (for Wisconsin late August through October).  This is important, as peony plants grow almost all of their root system in late fall.  Roots planted in spring depend on their reserves, since no new roots will likely be grown until fall.   Avoid planting in the spring! 

The roots, which will have next year's eyes located on the crown in late summer, should be placed in a hole that will easily accommodate them.  Squeezing the roots in to the hole could cause the peony to heave if surrounding soil is hard.    It is best to plant herbaceous peonies with the eyes no deeper than 2" below the soil surface.  If planted too deeply the plant may not grow and flower properly.  Most peonies are sold as bare roots in the fall and will have the stems cut off or removed.  When planting we advise spreading the roots evenly throughout the hole and filling it two-thirds full of soil, then water to help the soil settle.  Fill the remainder of the hole with soil and water again.  In another week or two come back, make a slight mound over the plant, the mound will settle over the winter and your peony hole will not become a depression for collection of water over the winter and spring.  During the first winter it is also recommended that the peony be mulched so that frost does not heave it out of the ground in the spring.  During the following years it is not necessary to mulch the plant for protection.

Many a gardener has been tempted to purchase the largest clump of peony they can find in hopes that the plant will flower the next spring.  While the clump does usually bloom the next spring, it may not the following year and then go slowly into decline.  The reason for this is that the plant needs room to grow new roots and this space is taken by large older roots that are storage vessels.  There also appears to be a need to reset itself when being transplanted, thus the standard 3 to 5 eye peony is the best choice for long-term performance.  In recent years we've encountered gardeners and a couple of commercial growers who indicate that they have had good experiences with the transplant of large clumps, unfortunately our experience has been completely opposite of this.  Again, our long-term plantings have always done best with divisions that do not have extensive root systems when planted.  This is likely true since divided plants will readily grow a new root system that will not have older roots around them that may transfer disease or compete for space.

Special attention should be given in the fall to cutting down herbaceous peonies and removing the stems and foliage from the area of the planting.  Peonies can get a fungal disease called botrytis, which shows up as black areas on stems and leaves during damp or wet weather.  To avoid incubating this disease, through old foliage, it is wise to remove foliage in the fall.

During the summer months peonies do not make much growth above ground, having done the majority of this work earlier in the spring.  Old flowers can be removed, but allow the foliage to stay on the plant as long as possible.  Peonies may look like they are doing very little during the hot days of summer, but they are busy storing food for the next year.  The plants in our gardens remain handsome throughout the summer and make a nice green shrub.  In autumn many of them produce leaves of gold, orange and red--adding to their value as a three season plant.

Fertilizing peonies can be done in the fall, but a soil test should be done if chemical fertilizers are to be used.  High nitrogen fertilizer should be avoided as it will cause excessive plant growth without flowering.  In most instances peonies need little fertilizing if the soil is good.  Avoid planting peonies in places that have had peonies growing in them previously.   Peonies utilize micronutrients in the soil that are depleted over time and planting them in this soil will produce poor plants.   Diseases may also be contained in soil that previously grew peonies and this can infect new plantings. 

Many of the hybrid peonies have strong stems and do not require staking or the placement of rings to keep them from flopping.  The older lactifloras may need some assistance with support, but are well worth the effort.  If you do not want to deal with plants that need support, ask or look at descriptions to avoid them.

The coral or salmon-colored hybrids are often very fragrant, some might even say stinky.  In any event they are excellent cut flowers and will certainly bring enjoyment to those gardeners interested in fragrance.  

In summation, herbaceous Peonies are outstanding, long lived plants that will likely remain long after we are gone, if some basic care is provided.  We have plants on our farm that were hybridized in the 1800's and some that were grown by my Grandfather in Brandon, Wisconsin.  We enjoy them as much today as he did 50+ years ago.

 

Intersectional (Itoh) Peony Culture

Planting is the same as for herbaceous Peonies, but they may be planted somewhat deeper.  A deeper planting tends to encourage new stems and a wider spreading plant over time.  A 4 inch planting from the top of the plant to the soil surface is usually a productive depth.  The crown and root systems on these plants can be quite variable in structure and size and are often difficult to fit into regular shaped planting holes.   Laying the plant on a 45° angle often makes planting easier and plants grow very nicely after this treatment.

Foliage should be cut to the ground at the end of the growing season and removed from the garden to avoid disease problems in subsequent years.  When removing stems in the fall one may notice buds along the stems, much like their woody peony parents have.  If one has the ambition, the largest and lowest buds on the stems may be grafted (as you would a woody peony) to produce more of the cultivar. We know from trials that buds that come from ground level or near that point are most likely to produce successful grafts.   Grafting these plants has not produced a high percentage pf 'takes' for us, but we have experienced enough positive results to know that it is a viable practice.  More work needs to be done grafting these plants to perfect a productive technique.

Intersectionals seldom, if ever, produce seed, even though their large carpels (seed pods) look as though they are full of them.  Gardeners that are not interested in seed production may simply cut these seed heads off after flowering to produce a neat looking shrub for the remainder of the summer months.  If by chance an Intersectional produces seed, one should carefully plant the seed and attempt to grow it to blooming size.  Many Intersectional hybridizers believe that the few plants produced from this seed will lead to more fertile generations of plants which will allow further development of this wonderful hybrid. 

Some of the best varieties available are 'Bartzella'--yellow, 'First Arrival'--pink, and 'Viking Full Moon'--luminescent cream-yellow-pink blend.  All are very hardy and as easily grown as herbaceous peonies in our cold Wisconsin climate.  

One negative aspect of this group is the propensity for genetic mutation.  Quite simply some plants change characteristics in floral form.  This often manifests itself as flowers with narrower petals, or few petals at all.  Once this process begins, aberrant flowers appear in greater numbers on the clump over the years, resulting in an inferior display.  Some cultivars are more prone to this than others, while some, like 'Bartzella' have never shown this affliction.  Notable plants that have shown mutation are:  'Lafayette Escadrille', 'Yellow Emperor', 'White Emperor', 'Rose Fantasy', 'Rosey Prospectus', 'Raggedy Ann' and 'Watermelon Wine'.

 

Woody (Tree or Shrub) Peony Culture
 

Tree Peonies....suffruticosa, rockii and hybrids and lutea hybrids

Tree Peonies have been grown for centuries in China and Japan.  These plants are mainly of the diverse species suffruticosa (with some rockii genetics).  In Japan they are referred to as 'Moutan' (Bouton)  and in China 'Mudan'.   They are among the most cherished plants in these nations and should receive much greater attention in American gardens.  Many cultivars available are historic hybrids that may be hundreds of years old, giving testimony to their durability.  The Japanese and Chinese suffruticosa selections are less tolerant of wet conditions and are often damaged during rainy seasons, especially in heavy soils. Plants originating from China have typically been the most available at low prices.  Unfortunately the plants were genetically selected to grow best in semi-arid conditions--making them a poor choice for most American gardens.  The Chinese suffruticosas are certainly beautiful, but have also caused many an American gardener to regard woody peonies as difficult to grow.  

The rockii hybrids are gaining popularity for their gorgeous flowers that exhibit dark basal flares.  Flowers are often carried on stout woody stems that grow somewhat taller than other woody peonies in northern climates.  Plants are quite cold hardy and typically establish more slowly than other woody peonies.  This group of woody peonies grows quite well in Wisconsin and other northern tier gardens.  A little time and patience will reward the gardener with a tremendous display of flowers each spring.

The lutea hybrids have the widest range of color, ranging from deep red, pink, lavender, yellow to coral and orange blends. Flower forms are as diverse as their colors, exhibiting single, double and semi-double with a variety of petal forms.  
Relatively new, the lutea hybrids are somewhat less cold tolerant than the Japanese and rockii varieties, but can be successfully grown in Wisconsin in most locations (USDA Zone 4, perhaps lower).   During very cold winters, above ground stems are often lost, but are replaced the following spring with growth from below ground level.  The new growth often produces good bloom and plants show no overall affect from the prior bad winter conditions.  The species delavayii and lutea are tender in Wisconsin and are not easily grown without special considerations.  The hybrid plants themselves tend to be shorter growing than the other woody peonies and often produce more stems from below the ground (a good thing).  Leaf structure varies widely from cultivar to cultivar and is often quite ornamental.

Shrubby woody plants, tree peonies don't actually fit the name commonly given to them.  Most range in height from 2' to 4' and some can go to 8' or more.  Many woody persistent stems typically make up a plant that usually spreads as much as its height, or greater.  Woody peonies are generally very hardy plants that can be grown successfully in zones 3 to 7,  but do best in zones 4 through 6.   

Plant growth is relatively slow and it may take certain cultivars 3 or more years to mature into flowering plants.  Young tree peonies often do not bloom true to form and will only show fully developed and colored flowers on mature/established plants.  Once plants are established they may grow in one place in excess of 50 years. 

Tree peonies are typically propagated by grafting a scion (stem and bud) on to a peony root (usually a herbaceous peony root).  Grafted plants that are 3 years or older usually begin to bloom reliably and are developing their own root systems.  When purchasing grafted plants gardeners should watch for plants that have herbaceous leaves arising from their bases. Plants that have been imported from Japan or China are most likely to have this 'adventitious' root stock and should be avoided.   If this very different leaf type is detected, the eyes of this portion should be cut away below ground so that it does not overtake the woody peony.

Some woody peonies are grafted on to their own roots, which is desirable, but unlikely due to available root material.  Division of tree peony roots is not typically an option since plants tend to grow off a centralized root system, but certain varieties are better subjects for this type of propagation.  Marketers of woody peonies often tout 'own root' plants as being better than grafted plants.  In truth, the grafted plants tend to establish more quickly and are able to withstand adverse soil conditions more easily.  Own root plants have an upside though, the gardener would never have to  remove an old herbaceous nurse root if it were to impede growth. 

Most plants available commercially are 1 to 5 years in age.  Larger, older plants are problematic due to their size and inability to establish as quickly and easily as their younger counterparts.  Older plants can be successfully transplanted if most of their woody stem structure is cut away.  Starting with younger plants tends to be most rewarding. One should not base a purchase on the number of stems a plant has.  Again a harsh cutback of woody stems is highly beneficial at the time of transplant.  Cutting away the woody stem structure may or may not destroy buds that would bloom the following year, but will also ensure that the plant survives and produces proportional stem to root structure after transplant.

Growing & Planting Tree Peonies...

Site Selection:  A site that drains well and is not in competition with large tree roots in a must.  The placement should get at least one half day of sun (preferably morning sun vs. afternoon sun) or bright filtered light.  The plant would prefer full sun all day, but the flowers last longer with some shade.  The soil should be loose and not compacted if possible.  Soils with high organic material are most preferred, but clay works well if it drains.  Gravel and sandy soils generally drain well, but are often missing nutrients important for tree peony growth.  Soils rich in lime seem to be best and Eastern Wisconsin is well known for this (underlying limestone).  Overly wet soils are probably a tree peony's worst enemy; in fact, a fairly dry location will suit the plant very well.  Since tree peonies do not generally like to be disturbed, select a planting place that will accommodate the plant for many years without movement.  Remember to allow plenty of space around the plant since in several years it could be large plant. 

Planting:  Start by digging a hole that will easily accommodate all of the peony's roots.  Do not squeeze the plant into the hole, as the roots may begin to grow and push the plant out of the ground.  Grafted plants should have the graft buried from 4" to 6" below the ground (or more), so that it is well protected from environmental changes.  Tree peonies are best planted much deeper than their herbaceous relatives--this often promotes growth from below ground and creates a fuller looking plant.  We've found that burying the root system to 6" or more (this means some of the stems are buried as well) will allow the stems to root quickly and branch below the ground.  Many of our plants will have only an inch or less of stem above the ground after planting them!   It is not unusual for tree peonies to arrive in the mail with most of the stems cut off or completely cut off, leaving only roots and some eyes.  This is very beneficial to the plant, as it will grow new stems the following growing season that are appropriate in size for the plant's root system to get a good start.  Typically, plants that arrive with many branches will loose these older stems over first or second winter or will not prosper.  Fill the hole approximately 3/4 full of earth around the plant and water the soil thoroughly so that all air pockets are removed.  Proceed to fill in the remainder of the hole with soil and add water as you fill.  Lightly press down the soil around the plant with your hands once you have finished.  Give the plant a couple of inches of mulching the first year to keep a more even temperature and moisture level around the plant.

Care: Generally tree peonies do not require much care after their first season.  During the first winter it is wise to mulch the plant so that it is not moved around by spring freeze thaw cycles.   We mound soil on top of our first year plantings in the field.  This has proven successful in getting the plants through their first winter.  Watering during very dry periods during the following summer may be needed until the plant's root system establishes itself.  Once the plant is established very little care and watering will be needed.  If watering is necessary during extreme drought, water the base of the plant not the foliage.   

Tree peonies, like all peonies, can get botrytis, a fungal disease which appears as black spots on the foliage or stems.    Wet conditions can cause this fungus to be problematic and the best treatment is prevention. Keep the plants on the dry side and well ventilated.   If fungus becomes a problem, cut away all diseased parts and throw them in the trash.  Commercial fungicides may also be used and a local garden center should be consulted (copper sprays tend to be most effective).   Fall cleanup of the peony leaves is also a good method of avoiding this problem.  

Fertilizing may be necessary at some point.  Avoid high nitrogen fertilizers as this will cause excessive foliage to be made at the expense  of flowering.  It appears that tree peonies like limey soil with a PH from 6.5 to 7.5.  A bit of agricultural lime sprinkled around the base of the plant has been said to produce better growth the next year.   A soil test is a good idea if you suspect that your plant is missing something nutritionally.  A dressing of composted manure in a wide swath around the plant will do no harm and enrich the texture of the soil.

No winter protection on established plants should be necessary.  A tall plant may lose stems from time to time during very cold temperatures, but new growth will arise from the base of the plant, if planted deeply enough.  From time to time dead wood will need to be cut from the plant to keep it looking good.   Do not cut down tree peonies in the fall like you would a herbaceous or intersectional peony, since the woody stems carry some of the next year's flowering buds.  One exception to this would be if you would like more stems to arise from the ground.  In this case, cutting the woody stems to the ground encourages dormant buds below the ground to grow into stems the following season and sometimes these will bloom their first season, but more likely the next season.  We've used this tactic on plants that are in decline or have been slow to spread to the desired width.

The best transplanting time for woody peonies is fall, once next year's dormant buds have been made.  Roots on the plant are developing in late fall and continue long after the plants have lost their foliage.  Generally spring planting of peonies is not successful due to the lack of root growth during this period.  Plants that do not outright die from spring planting, will often show extreme wilting during summer and a lack of growth.  If they make it to fall alive, it is likely they will establish and grow the next year.    

The lutea hybrids are somewhat less cold tolerant than the Japanese  varieties, but can be successfully grown in Wisconsin in most locations.  The Japanese and Chinese suffruticosa selections are less tolerant of wet conditions and are often damaged during rainy seasons, especially in heavy soils.   The species delavayii and lutea are tender in Wisconsin and are not easily grown.

In summation, tree peonies are a wonderful long-term addition to a garden.  Some patience will be required while the plants mature, but in the long run they will be extremely rewarding and will likely become one of the 'favorite' plants in the garden.  Try them, you won't be disappointed.

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