Using high tunnels to provide peony with a longer growing season to increase productivity in northern latitudes and cold soils

Using high tunnels to provide peony with a longer growing season to increase productivity in northern latitudes and cold soils

Summary

The purpose of this experiment is to evaluate growth and productivity of herbaceous peonies growing with and without late-season high tunnels. The peonies are growing on cold permafrost soils on a north-facing slope. We anticipate that high tunnels will warm soil and air temperatures, promote soil drying and provide an environment that will maximize plant growth and productivity on marginal sites. By extending the growing season, we expect there to be more carbohydrate storage in the roots and a more vigorous plant the following year.

The high tunnel experiment consists of six plots with three replicates under high tunnels and three replicates not covered. Each plot of (at least 30 plants) ‘Sarah Bernhardt’ peonies are planted in raised beds with double rows, 18 inches between plants and between rows. Each replicate consists of two double rows, 28 feet long, separated by a two foot aisle. There is at least a 10 foot buffer between treatments to minimize effects of high tunnels on adjacent plots. Rows are irrigated using thin wall trickle tape irrigation. Fertilizer consists of 20-20-20 broadcast in the spring and 8-32-16 broadcast in the fall at a rate of 50 pounds per 3,000 ft2. Plots are hand-weeded as needed. Roundup is used in areas with no peony plants.

The high tunnels are installed but not covered until after blooms have been harvested. The tunnels remain covered until a frost kills the vegetation or the ground freezes, then the cover is removed to put on straw mulch, as well as to allow adequate snow cover. Tunnels will be re-covered each year after blooming.

Data on soil and air temperature, soil moisture, relative humidity, PAR and rainfall will be collected using Hobo weather station (Onset Computer) recorded hourly throughout the year. Data on plant growth will consist of non-destructive analysis: flowering phenology, number of cut stems per plant, stem length, number of vegetative shoots per plant, and a analysis of cut flower quality (to be defined). Biomass samples will be collected from five plants per plot at the time high tunnel covers are removed for the winter. Observations will also be made on disease and insect pests inside and outside of high tunnels.

Objectives/Performance Targets

We expect to see differences in the production of the peony plants inside the high tunnels as early as next summer, with more stems to harvest and a more robust plant.

Accomplishments/Milestones

During the 2011 growing season, we grew the plants we had moved into the plot areas no different than our other peonies. We lost some plants in the plot areas, but only two were plants that are used for collecting data. I did not harvest any stems from the plants used for collecting data. The sides were dropped on the high tunnels on July 24, 2011. On bright sunny days, I rolled up the sides and opened the ends, but we closed them up by 10 pm when it was starting to cool off for the day.

We did not collect flowering data on these plants this year. We had a serious outbreak of botrytis that infected all the flower buds. We cut off those affected areas as they were noticed and did not have any blooms in the plot areas to harvest. Next growing season, a preemptive spraying of fungicides will be implemented in the whole field to control botrytis.

The plants inside the high tunnels did not develop botrytis faster or more severely once the sides were dropped in July. In fact, the plants appeared greener and healthier than those outside the tunnels. We expected the plants to stay green longer into the fall, and visually, they seemed to do that.

We downloaded data collected by the Hobo dataloggers on September 28. Also on September 28, we cut the tops off the peony plants. We collected our sample plants and took them to the university to be dried and have the plant dry weight from those plants for two growing seasons. As per instructions from Dr. Holloway, we rolled the plastic up and bungie tied it to the top support pipe on September 28. This will allow the plots to be covered with snow. We applied eight inches of straw mulch over the plots on October 2.

We hosted a farm tour for other potential peony growers on July 21, 2011. During this tour we showed our high tunnels and explained our project. We do not have any results to share yet, but we did explain what we had learned about building the high tunnels.

We hope to see a difference in the plants inside the high tunnels compared with those outside as early as next growing season. We will collect more data next summer on the number of stems and dates of bud development and harvest times in the plot areas.

Impacts and Contributions/Outcomes

So far we cannot demonstrate any benefits for producers, however, we are convinced the tunnels will make a difference in growing peony in marginal climates in Alaska. We are still unable to produce enough peony stems to meet the demand. We hope to show growers in the Fairbanks area that they can produce a vigorous plant and harvest as many stems as growers in warmer areas by putting the plants under high tunnels and increasing the length of the growing season.

• Tunnels as we started putting on the plastic.
• Farm tour day, showing one tunnel with plastic on and the sides rolled up and ends open.
• Tunnel all closed up.
• Moose made holes in the high tunnel before we removed the plastic from the tunnels.

Collaborators: