The late freeze in April 2007 that spread across much of the central and eastern United States had a big impact on oak mast here in Missouri (and presumably lots of other areas too). The freeze hit when a lot of oaks were flowering and killed the flowers and early leaves. Species with acorns that form in the first year (e.g. Quercus alba) had no production last year, but seemed okay this year. Species with second-year acorns (e.g. Quercus velutina) still produced in 2007 (from 2006's flowers) but didn't have any acorns this year.
I don't know if this could have affected oaks in the DC area. There was a paper in BioScience earlier this year about the late frost event (Gu et al., Bioscience 58(3):253-262) and their map doesn't show the heart of the freeze reaching DC, but the temperature was still below average. Nick Barber University of Missouri-St. Louis St. Louis, MO [EMAIL PROTECTED]
