The 2012 ASHS Annual Conference

Baldcypress [Taxodium distichum (L.) Rich.] and its varieties, Montezuma cypress (Taxodium distichum var. mexicanum G. Gordon] and pondcypress [Taxodium distichum var. imbricarium (Nutt.) H.B. Croom], constitute an increasingly popular group of trees for challenging built environments and urban forests.  In the nursery trade, these trees are largely seed propagated with minimal attention paid to provenance.  Provenance trials of related seedling populations of T. distichum for growth and tolerance to alkaline soils, drought, soil salinity, and foliar salinity exposure were conducted.  Clonal selections based on results from these experiments and phenotypic appearances were further screened for their propensity to root in sufficient quantities from shoot tip cuttings and to produce root systems of acceptable quality for commercial production.  Replicates of all or some of the 23 advanced clonal selections from this work were sent to ten participating trial sites in an east–west transect in USDA plant hardiness zones 8 to 10 stretching from Balm, FL, Quincy, FL, College Station, TX, to El Paso, TX.  A north–south transect from the USDA zones 8 to 10 Gulf Coastal sites through the central U.S. included Dallas, TX, Lubbock, TX, Fayetteville, AR, Haysville, KS, Columbus, OH, to Ames, IO in USDA zone 5a.  Montezuma cypress tended to grow larger more rapidly than baldcypress or pondcypress on moderate to warm winter sites.  Some Montezuma Cypress survived with minimal winter injury as far north as Kansas (–20 °C), while some species type baldcypress and genotypes from transitional populations between eastern provenances of baldcypress and Montezuma cypress from the Texas Hill Country survived –31 °C.  Studies are needed to confirm longer term cold tolerances.  Some clones of Montezuma cypress and the transitional Texas Hill Country populations had reduced foliar chlorosis compared to the species type baldcypress clones on high pH soils, but results were variable.  Severe to moderate foliar damage from Cercosporidium sequoiae (Ellis and Everth.) W.A. Baker and Partridge infections limited the potential for use of all clones tested at the Florida sites.