Effect of frosts on the mortality of common and cornwall forms of Oxalis latifolia Kunth

Abstract

Oxalis latifolia Kunth is not reported as a weed in those regions where the first centimetres of the soil get frozen in winter. The objective of this study is to evaluate the incidence of freezing temperatures on the mortality of common and cornwall form bulbs of O.latifolia in field conditions. 30 bulbs, 15 of each form, were planted 1 cm depth in two pots in April 2001 and they were placed outdoors in Azkoitia (northern Spain). Bulbs grew normally throughout the growing season and were harvested in January 2002. The lowest temperature reported in this period was -10ºC in December 2001. At the harvest all the found apical bulbs, whether they were common or cornwall, were dead. Among the lateral bulbs, 82% and 94% of common and cornwall form died because of frosts. The difference of mortality between the forms is explained by their morphology: common form bulbils grow over stolons some of which can bury the bulbils deeper in the soil and protect them from frosts; meanwhile, cornwall form bulbils are sessile and they have no choice of being buried and protected.