ISHS Acta Horticulturae 630: XXVI International Horticultural Congress: Nursery Crops; Development, Evaluation, Production and Use
ECOPHYSIOLOGY, PHENOLOGY, AND DEPTH OF COLD ACCLIMATION IN THE THREE SUBSPECIES OF ALNUS MARITIMA |
| Authors: | J.A. Schrader, W.R. Graves |
| Keywords: | seaside alder, subspp. oklahomensis and georgiensis, cold hardiness, tissue discoloration, woody landscape plant |
| Abstract:
Alnus maritima (seaside alder) is a woody plant with strong potential for use in managed landscapes. Because the natural distribution of the three subspecies of A. maritima is limited to areas with mild winter temperatures (USDA hardiness zones 7a and 7b), knowledge of cold acclimation and cold hardiness of these taxa is vital. Lab assessments of cold hardiness were performed seven times from 25 Sept. 2000 to 23 April 2001, by subjecting samples to cold-temperature ramping, and measuring the lowest survival temperature (LST) according to the tissue discoloration method. Samples were collected from indigenous plants of the three subspecies and from plants growing in a common garden near the border of USDA zones 4 and 5 in Ames, Iowa. Results indicate that some plants of all three subspecies can survive mid-winter extremes as low as -80 °C, that plants grown in Ames maintained a greater depth of cold hardiness and were more uniform in cold hardiness than plants growing in warmer native sites, and that the three subspecies did not differ in cold hardiness. Results of field trials with plots of 150 plants installed in each of three northern hardiness zones (USDA zones 5a, 4a, and 3a) supported these conclusions, showing survival of all 450 plants. By rating the percentage of tissue survival for each plant, we resolved differences between subspecies. Subspecies maritima, from the northernmost provenance (the Delmarva Peninsula), showed the least tissue death across all three plots (4% tissue death), followed by subsp. georgiensis from northwestern Georgia (10% tissue death), and then subsp. oklahomensis from southern Oklahoma (13% tissue death). Our results suggest that cold temperature stress should not limit the use of A. maritima in areas as harsh as USDA zone 3a. Selections based on cold hardiness may allow the use of A. maritima in areas with even colder winters. | |
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