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Archive for the ‘Herbaceous Peony Care’ Category

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.

The rockii tree peony 'Snow Lotus' has proven to be a very reiable grower in Texas over the last few drought striken years.

The rockii tree peony ‘Snow Lotus‘ has proven to be a very reliable grower in Texas over the last few drought stricken years.

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.

This picture was taken in May in the countryside outside Lanzhou city in China's northwestern Gansu province. This is the native habitat of the tree peony species P. rockii.

This picture was taken in May in the countryside outside Lanzhou city in China’s northwestern Gansu province. This is the native habitat of the tree peony species P. rockii.

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Tree peonies being irrigated in the spring in Gansu province, China.

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
  • 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.

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The time for digging and dividing herbaceous peonies has arrived and can be done anytime through early November. Do you have a large, old herbaceous peony clump that you would like to propagate? The best way to do this is through dividing the root system. This is a form of asexual reproduction, and yields a duplicate of the mother plant. Many plants are propagated this way such as hosta, iris and daylilies. Planting the seeds from a favorite peony variety is sexual reproduction and this will yield new plants which may not share the same attributes as the mother plant.

Dividing herbaceous peonies is fairly straight forward process with an end result that will gladden any gardener; more beautiful peonies to spread around the garden or share with friends.

Digging up a herbaceous peony

By this time of year, herbaceous peonies are not looking their best.

First cut the stems down, but leave 8” of stem to aid in pulling the roots out of the ground.

Dig around the ‘drip line’ of the peony. For a large clump, this is at least 15” away from the center of the plant. We like to use a heavy duty fork, but a shovel will also do just fine.

Get your digging tool under the root system and gently pry. Do not be impatient to get it out of the ground. Take the time to dig around the clump a few times to loosen the soil and the roots.

Use the stems to ease the roots out of the ground.

Rather than pulling straight up, work it from the sides. Freshly dug peony roots are very brittle.

Dispose of old peony leaves outside of your garden. If you leave them to compost in the garden, any harmful fungi on the leaves will colonize in the compost and only spread further in the garden next year. Old peony leaves can also be burned.

Thoroughly wash off the root system. Cover with a damp towel or tarp and allow to sit overnight. This will soften up the roots and make the task of dividing much easier.

Dividing a herbaceous peony

Peony dividing tools and supplies.

Supplies:

  • Isopropyl alcohol and paper towels for sterilizing dividing tools
  • Garden clippers
  • Assortment of old knifes of various sizes; a paring knife and large cutting knife do well
  • Linoleum knife
  • Rubber Mallet

After letting your roots soften overnight, begin by cleaning up the remaining stems so you can see the eyes and how the roots intertwine. The ‘eyes’ are the bullet shaped pink buds which grow from the crown of the plant. Each ‘eye’ represents a stem and potentially flowers for next year. 

In order to grow well, a new division needs ample roots. Too many eyes with just a little root will be unbalanced and struggle to thrive.

Use the large knife with the aid of the mallet to make your first big cuts.

Make further cuts as necessary with a smaller knife.

After making your cuts, gently pry the pieces apart, carefully untangling the roots.

Cut off any roots with black spots.

Use the linoleum knife to further clean any lesions on the divisions.

Four new peonies out of one. These could be further divided, but we like to have at least 4 eyes per division, suggested minimum is two. New divisions may or may not flower the following spring, depending on the amount of root present. If there are flowers, most likely they will be significantly smaller than a the plant will produce after 2-3 years of undisturbed growth.

If all this seems a bit to much for you, there is the more primitive, but also effective method I like to call the “old farmer technique” of dividing herbaceous peonies.

Dig up clump.

Take good aim with a sharp shovel….

The results are not as precise but the process certainly more expeditious.

Now its time to plant your new divisions. Remember that the ‘eyes’ should be no more than 2” beneath the soil (shallower in warmer climates). Check back next week for a post on planting herbaceous and tree peonies.

‘Itoh’ or intersectional peonies are also propagated by division. Since the crowns of these hybrids are very dense and woody, its best to let them dry out for at least a day before attempting to divide.

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We generally leave a few inches of stem in the fall so its easy to find our herbaceous peonies in the spring even when they are covered with mulch and the eyes are just beginning to peak through.

Uncovered, and coming up nicely.

A blend fertilizers and soil amendments for successful peony growing.

At Cricket Hill Garden we use these three soil amendments in combination around all of our peonies in the spring. We use the lime to raise the pH of the soil. Our natural pH is around 5.5, but with regular application of lime we have succeeded in raising it to around 6.5, the minimum threshold for good peony growth. We like to use calcitic lime because it contains a much higher percentage of calcium than regular garden lime. Calcium is a vital mineral to have in the soil; it helps the plants to form strong cell walls which are naturally more resistant to stress and disease. Calcitic lime also contains very little magnesium. Too much magnesium in the soil can render certain nutrients present in the soil unavailable to plants. Azomite, a crushed volcanic rock powder, contains 70 different minerals and trace elements. These micro-nutrients help facilitate healthy plant growth. We have found to be an excellent supplement for our peonies, other perennials as well as in the vegetable garden. Finally, we add a handful of low nitrogen fertilizer to the drip line of the peonies. We like to use North Country Organics Prostart. It is blend of greensand, bone char, sulfate of potash, non-Chilean nitrate, vegetable protein meal and animal protein meal such as feather meal. Again, this fertilizer is also very good for giving seedling transplants in the vegetable garden an extra boost of energy. Another good organic fertilizer to use would be Espona Bulb-tone (3-5-3).

Mixture of lime, azomite and fertilizer is spread around the the drip line of the plant.

The soil amendments are lightly worked into the ground.

This final step of ‘scratching’ the soil amendments and fertilizer into the ground is very important. If simply left on the surface, they will cake and not break down into the soil as quickly.

In a week or so we will begin fertilizing the peonies with Neptune’s Harvest and also begin spraying with the organic fungicide Actinovate, so check back soon for a post on that.

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