Flood-Tolerance Ranking of Red and Freeman Maple Cultivars

"Red maple (Acer rubrum) is often recommended for use in wet soils, yet its extensive native range suggests there may be genetic variation for traits associated with flood tolerance. Likewise, genetic variation for flood tolerance may be captured within red maple cultivars making some more appropriate than others for use in wet or low oxygen soils. Seven red maple cultivars (2-year-old trees)-Autumn Flame®, Bowhall, Karpick, Northwood, October Glory®, Red Sunset®, and Schlesinger- and 4 Freeman maple (A. freemanii) cultivars-Armstrong, Autumn Blaze, Morgan, and Scarlet Sentinel™, were ranked for flood tolerance by flooding the trees and characterizing photosynthesis, lenticel intumescence, and survival. Indicator trees representing the wet extreme of red maples native range were also included for comparison. Net photosynthesis declined for all cultivars; however, Schlesinger, Red Sunset and Bowhall had the highest net photosynthetic rates (ranging from 1.94 to 1.71 µmol/m2s) after 45 days of flooding. In contrast, Karpick, Autumn Flame, and Northwood had net photosynthetic rates near 0. The extent of lenticel intumescence also varied among the cultivars with Schlesinger and Bowhall producing the longest lenticels. All of the Northwood trees died, as did two-thirds of the Autumn Flame trees. The cultivars were separated into 3 overall flood-tolerance rankings: high (Schlesinger, Red Sunset, and Bowhall), intermediate (Armstrong, Morgan, October Glory, Scarlet Sentinel, and Autumn Blaze), and low (Karpick, Autumn Flame, and Northwood)."