The Effectiveness of Selected Mulching Techniques And
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Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1980 The effectiveness of selected mulching techniques and antitranspirants in the prevention of cold injury for five species of container-grown evergreen nursery stock Frank David Gibbons III Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Agriculture Commons, and the Plant Sciences Commons Recommended Citation Gibbons, Frank David III, "The effectiveness of selected mulching techniques and antitranspirants in the prevention of cold injury for five species of container-grown evergreen nursery stock " (1980). Retrospective Theses and Dissertations. 7328. https://lib.dr.iastate.edu/rtd/7328 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. 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Requests can be made to our Dissertations Customer Services Department. 5. Some pages in any document may have indistinct print. In all cases we have filmed the best available copy. UniversiW Microllms International 300 N. ZEEB ROAD. ANN ARBOR, Ml 48106 18 BEDFORD ROW, LONDON WC1R 4EJ, ENGLAND 8012961 GIBBONS, FRANK DAVID, III THE EFFECTIVENESS OF SELECTED MULCHING TECHNIQUES AND ANTITRANSPIRANTS IN THE PREVENTION OF COLD INJURY FOR FIVE SPECIES OF CONTAINER-GROWN EVERGREEN NURSERY STOCK Iowa State University PH.D. 1980 University Microfilms Internâti On &l 300 N. Zeeb Road, Ann Arbor, MI 48106 18 Bedford Row, London WCIR 4EJ. England PLEASE NOTE: In all cases this material has been filmed in the best possible way from the available copy. Problems encountered with this document have been identified here with a check mark . 1. Glossy photographs ^ 2. Colored illustrations ^ 3. Photographs with dark background '4. 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Other Iniversi^ Microfilms Ttemational The effectiveness of selected mulching techniques and antitranspirants in the prevention of cold injury for five species of container-grown evergreen nursery stock by Frank David Gibbons III A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Major: Horticulture Approved; Members of the Committee Signature was redacted for privacy. Signature was redacted for privacy. n "Charge of Major Work Signature was redacted for privacy. Signature was redacted for privacy. Ftjf the Major Department Signature was redacted for privacy. Signature was redacted for privacy. hor the ur lova state University Ames, Iowa 1980 11 TABLE OF CONTENTS Page GENERAL INTRODUCTION 1 GENERAL LITERATURE REVIEW 2 EXPERIMENTAL DESIGN 26 PART I. THE EFFECTS OF SELECTED MULCHING TECHNIQUES ON THE MODIFICATION OF ROOT ZONE TEMPERATURES AND SURVIVAL OF FIVE SPECIES OF CONTAINER-GROWN EVERGREENS 33 INTRODUCTION 34 MATERIALS AND METHODS 43 RESULTS AND DISCUSSION 51 PART II. THE EFFECTS OF ANTITRANSPIRANTS ON THE PRE VENTION OF WINTER DESICCATION OF CONTAINER- GROWN EVERGREENS AND A SCANNING ELECTRON MICROSCOPIC EVALUATION OF THEIR PERFORMANCE 74 INTRODUCTION 75 MATERIALS AND METHODS 83 RESULTS AND DISCUSSION 86 GENERAL SUMMARY AND CONCLUSIONS 123 LITERATURE CITED 130 ACKNOWLEDGMENTS 142 APPENDIX 145 1 GENERAL INTRODUCTION The practice of starting trees and shrubs in containers has several advantages over other nursery production methods. It allows for a longer selling season, a smaller growing and holding area, and the possibility of carrying unsold plants over for another growing and sales season. Less transplanting shock is also reported for container-grown plants (Pirone, 1972). Disadvantages are: (1) size of plants is limited; (2) plants may become potbound; and (3) inability of some plants to successfully over winter in northern climes. My research was initiated in 1977 at Iowa State University to in vestigate the overwintering problem which Mehlquist (1969) considered one of the most difficult phases of nursery production. This study, using evergreen plants, was designed to investigate two questions: (1) Is it possible to successfully overwinter container-grown plants in a field environment by the application of selected mulches? (2) Are antitranspirants effective in reducing winter burn? It was the objective of this investigation to identify mulching techniques and antitranspirants which could be used alone or in combina tion to reduce the winter injury of container-grown evergreens in Iowa. 2 GENERAL LITERATURE REVIEW Plant Hardiness A comprehensive review of the plant hardiness literature will not be undertaken since several excellent reviews have already been published on the subject (Levitt, 1941; Scarth, 1944; Chandler, 1954, Mazur, 1969; Weiser, 1970; Li, 1978). This review includes the most recent work, in addition to investigations pertaining to evergreens and container-grown stock. Cold resistance Cold hardiness, cold acclimation, frost resistance, and cold resis tance are terms referring to the degree of resistance to winter damage that plants can develop. Flower bud injury, bark splitting, root injury, desiccation, and foliage injury were types of winter damage noted by Davis (Seidel, 1976) In relation to overwintering container-grown nursery stock. The degree of cold resistance depends on several factors although heradity is one of the most Important. Many plants simply lack the in herent capability to acclimate to temperate environments. Environmental stresses, particularly drought and low temperatures, control the distri bution and productivity of plants on earth (Weiser, 1978). Some plants sustain what Lyons (1973) refers to as "chilling injury" when exposed to temperatures below 10°C. Many woody plants are able to withstand tem peratures to at least -40°C (Rajashekar and Burke, 1978). Hardened woody plant twigs have survived immersion in liquid helium, -269°C (Sakai , 1962). 3 The acclimation process Hardiness Is also influenced by the amount of cold acclimation that has occurred. Li (1978) defines cold hardiness as "the seasonal transi tion from a tender to a hardy condition," Since hardiness is a seasonal phenomenon, It probably occurs in response to certain environmental cues. In alfalfa, Tysdal (1933) found a correlation between the natural condi tion occurring in the fall, i.e., decreasing day length and alternating temperatures, and the effects of similar factors on the hardening process under controlled laboratory conditions, McCreary et al. (1978) found that artificially shortening the daylight periods substantially increased the level of hardiness, but relatively low levels of light leakage greatly reduced this hardiness. These results Indicate that a controlled photo- period can be an effective tool for raising Douglas-fir seedlings in green houses In the Pacific Northwest when off-season planting or multiple crop ping is desired. Irving and Lanphear (1967) concluded that acclimation was photoperiodically controlled in Acer and Viburnum. They found that plants exposed to low temperatures during the dark period with long days would reach a degree of hardiness