Growing Peonies in USDA Zones 8 and 9

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 five 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.)

In the 2011 drought and 2012’s unprecedented heat wave, all plants have suffered.

One gardener reported that over the summers of '11 and '12, 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 reliable grower in Texas during 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.

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.

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 herbaceous peonies receive enough winter chill to bloom reliably. The exception to this, are some of some very late season varieties which tend to quickly wither in the heat of early June.

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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