Horticultural Applications of a Newly Revised USDA Plant Hardiness Zone Map Mark P
Total Page：16
File Type：pdf, Size：1020Kb
NCRPIS Publications and Papers North Central Regional Plant Introduction Station 2-2012 Horticultural Applications of a Newly Revised USDA Plant Hardiness Zone Map Mark P. Widrlechner United States Department of Agriculture, [email protected] Christopher Daly Oregon State University Markus Keller Washington State University Kim Kaplan United States Department of Agriculture Follow this and additional works at: http://lib.dr.iastate.edu/ncrpis_pubs Part of the Agricultural Science Commons, Agriculture Commons, Agronomy and Crop Sciences Commons, and the Horticulture Commons The ompc lete bibliographic information for this item can be found at http://lib.dr.iastate.edu/ ncrpis_pubs/5. For information on how to cite this item, please visit http://lib.dr.iastate.edu/ howtocite.html. This Article is brought to you for free and open access by the North Central Regional Plant Introduction Station at Iowa State University Digital Repository. It has been accepted for inclusion in NCRPIS Publications and Papers by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Horticultural Applications of a Newly Revised USDA Plant Hardiness Zone Map Abstract The ca curate prediction of winter injury caused by low-temperature events is a key component of the effective cultivation of woody and herbaceous perennial plants. A common method employed to visualize geographic patterns in the severity of low-temperature events is to map a climatological variable that closely correlates with plant survival. The .SU . Department of Agriculture Plant Hardiness Zone Map (PHZM) is constructed for that purpose. We present a short history of PHZM development, culminating in the recent production of a new, high-resolution version of the PHZM, and discuss how such maps relate to winterhardiness per se and to other climatic factors that affect hardiness. The new PHZM is based on extreme minimum-temperature data logged annually from 1976 to 2005 at 7983 weather stations in the United States, Puerto Rico, and adjacent regions in Canada and Mexico. The PHZM is accessible via an interactive website, which facilitates a wide range of horticultural applications. For example, we highlight how the PHZM can be used as a tool for site evaluation for vineyards in the Pacific northwestern United States and as a data layer in conjunction with moisture-balance data to predict the survival of Yugoslavian woody plants in South Dakota. In addition, the new map includes a zip code finder, and we describe how it may be used by governmental agencies for risk management and development of recommended plant lists, by horticultural firms to schedule plant shipments, and by other commercial interests that market products seasonally. Keywords winter injury, zip code, GIS, minimum temperature, Vitis, climate Disciplines Agricultural Science | Agriculture | Agronomy and Crop Sciences | Horticulture Comments This article is from HortTechnology 22, no. 1 (February 2012): 6–19. Rights Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The onc tent of this document is not copyrighted. This article is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/ncrpis_pubs/5 when plant tissues optimally achieve a maximal degree of cold acclimation, extreme low-temperature events may still overwhelm adaptive survival mech- anisms. 3) And finally, during the late winter and early spring, plants may deharden when exposed to tempera- tures above freezing, having satisfied physiological rest requirements (Litzow Feature and Pellett, 1980), and can then suf- fer damage from subsequent low- temperature events. Studies that thoroughly document the seasonal progression of acclimation and provide graphical representations of the timing of actual or potential injury Horticultural Applications of a Newly Revised from low-temperature events at all three stages in the annual cycle include those USDA Plant Hardiness Zone Map by McNamara et al. (2002), McNamara and Pellett (1993), Mills et al. (2006), 1,5 2 3 Scheiber et al. (2002), Schrader and Mark P. Widrlechner , Christopher Daly , Markus Keller , Graves (2003), Szalay et al. (2010), and Kim Kaplan4 and Va¨ino¨la¨ et al. (1997). Hardiness-zone basics ADDITIONAL INDEX WORDS. winter injury, zip code, GIS, minimum temperature, Of the three stages when injury Vitis, climate often occurs, the frequency and se- SUMMARY. The accurate prediction of winter injury caused by low-temperature verity of midwinter, low-temperature events is a key component of the effective cultivation of woody and herbaceous events have historically received con- perennial plants. A common method employed to visualize geographic patterns in siderable attention by plant scientists. the severity of low-temperature events is to map a climatological variable that closely Specific weather events causing plant correlates with plant survival. The U.S. Department of Agriculture Plant Hardiness injury on a case-by-case basis may yield Zone Map (PHZM) is constructed for that purpose. We present a short history of insights on factors influencing adap- PHZM development, culminating in the recent production of a new, high- tation [see Bachtell and Green (1985) resolution version of the PHZM, and discuss how such maps relate to winter- for an example from the Chicago hardiness per se and to other climatic factors that affect hardiness. The new PHZM region and Gu et al. (2008) for a de- is based on extreme minimum-temperature data logged annually from 1976 to 2005 at 7983 weather stations in the United States, Puerto Rico, and adjacent tailed discussion of the Spring 2007 regions in Canada and Mexico. The PHZM is accessible via an interactive website, freeze in the eastern and central United which facilitates a wide range of horticultural applications. For example, we States], but such weather events are highlight how the PHZM can be used as a tool for site evaluation for vineyards in not repeatable and do not lend them- the Pacific northwestern United States and as a data layer in conjunction with selves to experimentation and hypoth- moisture-balance data to predict the survival of Yugoslavian woody plants in South esis testing. However, further insights Dakota. In addition, the new map includes a zip code finder, and we describe how it can be gained by shifting emphasis may be used by governmental agencies for risk management and development of away from individual weather events recommended plant lists, by horticultural firms to schedule plant shipments, and by (or even seasons) to longer time frames other commercial interests that market products seasonally. that document multiple, extreme events on a climatic scale. Heinze and Schreiber orticulturists have long recog- plants,’’ so the ability to forecast the (1984) presented a comprehensive re- nized that the accurate pre- risks associated with such factors is ex- view of this topic, detailing the history Hdiction of winter injury is a tremely valuable. and application of long-term climato- key component of the effective culti- Freeze injury to various plant tis- logical data to relate patterns of woody- vation of long-lived woody and herba- sues and organs typically occurs at three plant adaptation to low-temperature ceous perennial plants in many climates. stages in the annual cycle (Larcher, injury. Winter injury can limit long-term plant 2005; Raulston and Tripp, 1994): 1) A BRIEF HISTORY OF HARDINESS survival and vigor and can reduce During the autumn, when plants cease ZONES AND ZONE MAPS. A relatively production of valuable horticultural growth (Kalcsits et al., 2009) and begin simple method used to visualize geo- products, including flowers, foliage, to harden or acclimate to winter con- graphic patterns of the biological se- fruit, and seeds. As noted by Skinner ditions (often signaled by decreasing verity of low-temperature events is to (1962), ‘‘frost dates, length of the grow- photoperiod and temperature), early, map a climatological variable that closely ing season, and minimum winter tem- low-temperature events can exceed a correlates with patterns of plant sur- peratures are among the least readily plant’s (or a specific tissue’s) ability to vival. Rehder (1927) developed the controlled of the major factors gov- withstand the event. 2) During the first such map for the United States, erning the geographic adaptability of lowest temperatures of midwinter, with a mapped zonation system that 6 • February 2012 22(1) related winter minimum temperatures subsequent updates using more recent to represent areas with PH > 4.4 °C to the survival of specific woody plants. meteorological data appeared in var- (40 °F) that are essentially frost-free. He roughly divided the temperate ious publications in 1951, 1967, and Even in parts of the world that do not portion of the conterminous United 1971 (Wyman and Flint, 1985). normally experience freeze events or States and southern Canada into eight This lack of uniformity in zone a well-defined winter season, plants can zones based on the mean temperature intervals prompted the USDA Agri- experience chilling injury at tempera- of the coldest month, each zone span- cultural Research Service (ARS) to tures below about 10 °C (50 °F) ning 2.8 °C(5°F). develop its own ‘‘Plant Hardiness (Levitt, 1980). Thus, knowledge about Shortly thereafter, Kincer (1928) Zone Map’’ with zones defined uni- geographic patterns of ‘‘warmer’’ low- produced a similar map, but based in- formly by differences in the PH sta- temperature extremes is also horticul- stead on ‘‘the mean annual extreme tistic of 5.6 °C (10 °F) (USDA, 1960, turally valuable in frost-free regions minimum temperature’’ [the lowest 1965). Discrepancies between the zone and can provide guidance in colder temperaturerecordedin1year—herein designations of Wyman’s and USDA’s regions on how best to manage the referred to as the plant hardiness (PH) maps caused some confusion (Skinner, outdoor cultivation of tender plants statistic], scaled by 5.6 °C (10 °F) in- 1962), but the USDA’s consistent zone that experience chilling injury.