Improving production schedules for high-value perennial flowers in Utah: Peony

Peony (Paeonia spp.) production is important to early-season cut flower markets (Kamenetsky and Dole, 2012), and particularly as a high-value crop in local, smaller-scale operations. Peonies are well suited to temperate zones, where winter chilling followed by warming is sufficient for flower development (i.e. at least 70 days of chilling at 2-6oC) (Halevy et al., 2002). Much research to improve production has focused on chilling requirements for warm climates outside of the U.S (Fulton et al., 2001; Halevy et al., 2002). In the high-elevation and semi-arid state of Utah, however, growers face long winters that delay the growing season and amplify challenges to meeting early market demands. Therefore, understanding post-chill air and soil warming, as well as the effectiveness of season extenders to advance development, will help Utah growers meet key holiday market demands, such as Mother’s Day, and increase farm profitability.

Purpose

• Evaluated high tunnel and outdoor field production of peonies with yield timing and quality.
• Compare low tunnels, low tunnels with soil heating, and unheated controls within the high tunnels and field with yield timing and quality. 
• Develop flowering prediction models to schedule flower production that meets a specific marketing window and optimized flower yields in peony.
• Disseminate research findings from peony studies to growers, industry partners, and the wider horticultural community through journal articles, fact sheets, and workshops. 

Procedures

The field study is located at the Utah Agricultural Experiment Station – Greenville in North Logan, UT (41’ 77” N, -111’ 8” W) at an elevation of 4,780 ft. In 2011, 60 peonies (Paeonia lactiflora ‘Coral Charm’) were planted in an outdoor field and 60 peonies were planted in an adjacent high tunnel. We subdivided the field and high tunnel into a total of 18 plots (Figure 1). From these 18 plots, we evaluated six heating treatments in triplicate:

1) field (F) plus low tunnel (F: +LT -H)
2) field plus low tunnel and soil heating (F: +LT +H)
3) unheated field control (F: -LT -H)
4) high tunnel (HT) plus low tunnel (HT: +LT -H)
5) high tunnel plus low tunnel and soil heating (HT: +LT +H)
6) unheated high tunnel control (HT: -LT -H)

Preliminary Results and Discussion

Temperature Conditions

The 2019 peony harvest is complete within the high tunnel (HT) and in-progress in the field (F). Therefore, the reported preliminary results reflect only the high tunnel treatments. Because of the intensity of field work during this time, data presented are from only April—May 2019.

Overall, the near-surface soil temperature and canopy air temperature fluctuated less and were warmer in the HT versus F. Within the HT, the use of a LT and soil heating helped maintain nighttime temperature lows above freezing. Air temperature between the field treatments followed a similar pattern to the high tunnel. Soil temperature between the control and unheated LT treatments was more pronounced in the F than in the HT, particularly during the cool April weather.

Yield

The high tunnel advanced peony bloom by nearly one month and made it possible to meet the key Mother’s Day market window. The first peony harvest in the high tunnel began on 26 Apr. 2019, and ended on 17 May 2019. Conversely, the first peony harvest in the field began on 20 May 2019 and is near completion as of 10 Jun. 2019. Therefore, only the HT results are reported here.

Within the HT, peak production lasted from 26 Apr.—04 May 2019 with soil heating, 29 Apr.—06 May with only a LT, and from 02—12 May in the HT control (Figure 2). However, the number of culls increased with use of low tunnels and soil heating. We observed that any contact between the plant and low tunnel material resulted in a culled stem. Soil heating advanced plant maturity into late April, a time when LT are generally needed to avoid night time frosts in northern Utah. Therefore, a new challenge has emerged to create larger low tunnels that still effectively capture heat, while providing sufficient space for the plants. We are excited to trial new LT designs next year to reduce the number of culls, isolate whether the increase in culls resulted from heating effects or low tunnel contact, and begin modeling crop production schedules.

Lastly, we have begun to explore the economic markets in Northern Utah through collaboration with a local flower farmer coop that primarily sells to florists. In 2019, we sold Grade 1 and 2 peonies for $3/stem for purchases of 50 or more, and $5/stem for purchases of <50. All of our peonies sold out at these prices. As we repeat the trials in 2020, we expect to charge $4/stem for 100+ stems, $6/stem for <100 stems, and begin selling culls at a reduced price. Growing peonies is a promising new crop to diversify farms in Northern Utah.

 

References

Fulton, T.A., Hall, A.J., Catley, J.L. 2001. Chilling requirements of Paeonia cultivars. Scientia Hort. 89:237-248.

Halevy, A.H., M. Levi, M. Cohen, and V. Naor. 2002. Evaluation of methods for flowering advancement of herbaceous peonies. HortScience. 37(6): 885–889.

Kamenetsky, R. and Dole, J. 2012. Herbaceous Peony (Peonia): Genetics, Physiology, and Cut Flower Production. Floriculture and Ornamental Biotechnology. 6(1): 62-77.

Melanie Stock

Assistant Professor

Melanie Stock is Assistant Professor, Urban and Small Farms Extension Specialist, at Utah State University. Contact her at [email protected]