Question
Some years the oak trees in southeast Oklahoma produce huge yields of acorns.  Other years there are very few acorns, particularly on the oak trees in the higher elevations of the Kiamichi Mountian.  Is this based on precipitation or is there something else going on?  Is there a way to improve the acorn production of an oak tree?

Answer
Acorn crops can vary greatly from year to year. During 揾eavy?years, acorns can rain down from the trees, almost covering the ground beneath them. In 搒parse?years, one can travel from tree to tree and have difficulty locating more than a handful. The factors determining acorn production patterns are not well understood, but Koenig and Knops (1995) have demonstrated that weather at the time of flowering is likely an important contributing factor. Since oaks are wind-pollinated species, conditions during the pollination period that promote good pollen dispersal are believed to enhance acorn production. But there may also be other factors at work also. There are probably internal rhythms present within trees that also influence how many acorns are produced. In this instance, the almost total absence of white oak acorns last year may have contributed to good crops this year since trees were able to conserve resources that they are currently using to produce this abundant crop. Koenig et al. (1994) found a strong negative autocorrelation between crops from one year to the next which ?especially for blue oak - supporting the notion that crops one year (or the lack thereof) can influence crops the subsequent year.

Another interesting thing about acorn production is that there are species that take one season from flowering till acorns mature, and there are species that require two seasons. In general, species in the white oak sub-genera take a single year, while species in the red or black oak sub-genera, take two years.

Fertilization of individual oak trees may help increase acorn production. A complete fertilizer (such as 8-12-12) broadcast underneath mature oaks evenly away from the trunk and out to the dripline at the rate of 2 lbs per inch of diameter, at breast height (dbh) in the month of March (South) or April (North) may increase acorn production. Extra zinc (used by pecan growers at 3-5 lbs per mature tree and documented by research to improve nut production) may also be needed by oaks for improved acorn production.

Remember that fertilizer will impact the current year抯 white oak acorn crop and next year抯 red oak acorn crop, because these take an additional year to mature. Individual oaks located around lawns, pastures, croplands, and other fertilized areas have long been noted for heavier, more consistent acorn production, although other factors (such as insects or air circulation around crowns) may be involved.