2017 ASHS Annual Conference

A commonly planted oak in the landscape, pin oak (Quercus palustris), is known to develop iron deficiency-induced foliar chlorosis when grown in alkaline soils. In contrast, species and provenances endemic to alkaline soils do not always display this chlorosis. More environmentally tolerant and aesthetically pleasing taxa could be used if they are first screened to determine their adaptability to high pH soils. Over a seventeen-week period, this study evaluated Texas red oak (Q. buckleyi), durand oak (Q. sinuata var. sinuata), and two collections of pin oak [Wichita, KS (W) and Manhattan, KS (M)] to determine the extent of foliar chlorosis when grown in an elevated pH substrate. Acorns of each species were planted in one gallon containers in a substrate amended with either standard (2.4 kgŸm^-3; control) or high (11.9 kgŸm^-3) rates of dolomitic lime. Twice-weekly flowable lime drenches (26.7 mL of liquid calcium carbonateŸ L^-1 of water) were used to maintain substrate pH in the high lime treatment. In elevated substrate pH (7.0), pin oak had low SPAD values (19.1 Wichita and 16.3 Manhattan) and leaf chlorophyll concentrations (14.6, W and 11.8 μgŸcm^-2, M). In the control substrate, pH=5.3, pin oak maintained greater SPAD values (36.4, W and 36.9, M), and greater leaf chlorophyll concentrations (38.9, W and 39.9 μgŸcm^-2, M). Also, foliar iron content in both collections of control pin oak (1.1, W and 1.2 molŸL^-1, M) were greater than plants in the high substrate pH (0.8 molŸL^-1, W and M). Conversely, for Texas red oak, no differences in SPAD readings (31.7, control and high), chlorophyll concentration (35.8, control and 34.5 μgŸcm^-2, high), and foliar iron content (3.3, control and 1.7 molŸL^-1, high) were found between control and high substrate pH groups. Durand oak performed very similarly; no differences in average SPAD readings (37.0, control and 33.4, high), chlorophyll concentration (35.7, control and 29.0 μgŸcm^-2, high) and foliar iron content (2.4, control and 1.6 molŸL^-1, high) were found between control and high substrate pH groups. This study suggests that Texas red oak and durand oak are more capable of sequestering substrate iron than pin oak in a high pH substrate. These species should be evaluated further in field studies for their potential as more suitable species for use in landscapes with high pH soils.