Comparative winter frost resistance of plant species from southern Africa, Australia, New Zealand, and South America grown in a common environment (Dunedin, New Zealand)

Abstract

The foliar frost resistance of plant species from the Southern Hemisphere is generally less than that of their northern equivalents, but are there differences between species from different southern land masses? Frost damage was determined visually and from measures of chlorophyll fluorescence: the two methods gave similar estimates of frost resistance. Amajority of species had frost resistances that were in accord with frost hardiness ratings derived from USDA climate zones, but species assigned to warmer climate zones were often more frost resistant than expected. USDA climate zones, which are based on continental climates in the Northern Hemisphere, may need re‐evaluation for the oceanic climates in the Southern Hemisphere. The frost resistance of various plant species from New Zealand, Australia, South America, and South Africa was determined in a common environment in the Dunedin Botanic Garden and its environs during the Dunedin winter (June‐July 2005). South American species were the most frost resistant, followed by New Zealand, Australian, and South African species, which were generally the least resistant. Broadleaved trees and shrubs, and conifers, showed a similar pattern of resistance with respect to countries. These patterns were less consistent for families and genera and it was concluded that the climate of origin rather than taxonomic affinity determined the winter frost resistance of species sampled in the Botanic Gardens.