Mature female Maidenhair trees (Ginkgo biloba L.)have been observed to produce seed dispersal units in some years and none in other years. A temperature and/or photoperiod flowering threshold is suggested. Daily temperatures and daylengths at five Ginkgo sites in continental U.S. for January-April 1964-1974 were evaluated. A computer program was designed to estimate daily photothermal equivalent (PTE = temperature and photoperiod), and the magnitude and duration of the PTE in relation to a series of photothermal constants. Use of the data from production and nonproduction years provided a mathematical model for prediction of dispersal unit production. The model was tested with environmental data for additional sites recorded in the botanical literature.
Johnson, Michael I.
"Model for Estimating the Probability of Crop Production for Ginkgo biloba L.,"
Journal of the Arkansas Academy of Science: Vol. 29
, Article 16.
Available at: http://scholarworks.uark.edu/jaas/vol29/iss1/16