VEGETATIVE AND REPRODUCTIVE PHENOLOGY OF AFRICAN RUE (PEGANUM HARMALA) IN THE NORTHERN CHIHUAHUAN DESERT

摘要

African rue (Peganwn harmala) is an herbaceous perennial plant native to arid and semiarid regions of northern Africa and Asian deserts that has spread to parts of the southwestern United States and northern Mexico. Despite its occurrence in many geographic regions, little is known about the biology and ecology of this invasive species. We conducted field studies on 2 populations of African rue in the northern Chihuahuan Desert to describe its vegetative and reproductive phenology. Overwintering, dormant plants in both populations commenced growth in mid March, grew through May and June, and initially senesced during June and July. Shoot development was synchronous between the 2 populations, but was not related to ambient or soil temperatures or precipitation. Onset of senescence was not related to calendar date or accumulated temperature. Flower production commenced at both sites in mid April, and fruit maturation occurred in June and July. Fruit maturation was related to calendar date and ambienttemperature. In one population, senescent plants initiated new shoots in August and produced a second cohort of flowers. This renewed growth was not related to temperature, but likely triggered by midsummer precipitation. Therefore, African rue exhibitscharacteristic "drought evader" growth and reproduction strategies. This fundamental description of African rue phenology provides knowledge needed to manage this invasive species.