Posted by: HortAlaska | November 22, 2017

Irrigation and Peonies

Kopp, K/, R. Kjelgren, P., Urzagaste and X. Dai. 2017. Physiological and quality responses of turf grass and ornamental plants to weather-based irrigation control. International Turfgrass Society Research Journal. 13:537-546.

This article published out of Utah State and U of Florida was an interesting article testing weather-based irrigation controllers and plant growth. The researchers used three unrelated plants that have very different rooting habits: Kentucky bluegrass (Poa pretenses), an ornamental Euonymus (Euonymus alatus ‘Compactus’, and herbaceous peony, (Paeonia lactiflora). The purpose of the project was to learn if there was any water savings with the use of irrigation controllers that are programmed to take cues from Mother Nature on when to irrigate and how much. The experiment took place in North Logan, Utah where water certainly is at a premium. By using controllers that are programmed to fit the local weather patterns such as sunshine, rainfall events, evaporation rates, etc.  with plant water demand, they hope to make the entire use of irrigation water more efficient.

The weather controllers they compared were Hunter PC-300 controller with Solar Sync Sensor; Rainbird ESP-LX controller with Evapotranspiration Manager and Weathermatic SL-1600 controller.

The two year study did not provide quick answers for irrigation control in peonies. Plants suffered significant water stress under the regime programmed into the controllers. Although it is a great idea, this is more a cautionary tale. Water use in plants is very complex, and obviously the researchers need to do more studies to find the right combination of weather factors that might be used to predict water uptake in peonies. For now, growers cannot rely on pre-programmed irrigation systems to determine irrigation needs. For peony growers it’s back to the old eyeball test. Plant leaves do not show a color difference with lack of water. They droop every so slightly in midday. Severe water shortage is shown by significant leaf edge curling (upward) along the long axis. Stem length is also stunted by as much as 20-30 cm over the season. The first 5 years I grew peonies in Fairbanks, I did not irrigate and saw no symptoms of moisture stress. That does not mean irrigation was not necessary. They might have grown better with irrigation, but stress to the point of degradation did not occur. After 5 years, however, plants that had become established with very large root systems showed water stress every season beginning in mid June about 2 weeks before flowering.


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