Abstract
Unreliable flowering is the major constraint to sustained high crop yields in lychee (Litchi chensis Sonn.) trees. Insufficient exposure to cool ambient temperatures is the main environmental factor limiting flowering in mature quiescent trees. In south Florida, the warm subtropical climate is considered marginal to induce lychee flowering. Nonlinear regression analysis was used to test the yield responses of trees in 8 to 12 'Mauritius' lychee orchards to the total number of hours per year that orchards were exposed to ambient temperatures below 70, 65, 60, 55, 50, 45, or 40 F from 1999-2003 in Homestead, Florida. In addition, annual mean ambient temperatures in Homestead in November, December, and January 1999-2003 and the 30-year average temperature were related to annual fruit yields. As the number of hours below 55 or 60 F increased, the average crop yield increased. In years when the annual mean November through January temperatures were at or below the 30 year average, crop yields were greater than in years with above average November through January temperatures.
