Quantifying Potential Fruit Production by Three Common Clonal Shrub Genera in Eastern Hardwood Forests

Cathryn H. Greenberg^1,* and Douglas J. Levey²

¹USDA Forest Service, Southern Research Station, Upland Hardwood Ecology and Management Research Work Unit, Asheville, NC 28806. ²107 Westbury Road, McLean VA 22101. *Corresponding author.

Southeastern Naturalist, Volume 25, Issue 3 (2026): 341–354

First published early online: 12 August 2026

Abstract
Fruit crop-size estimates are little better than indices unless tied to plant abundance. We developed a “standardized fruit crop” (SFC) using 11 years of fruit-density data in replicated transects to estimate long-term average (versus within-year) production by Vaccinium spp. (blueberry), Gaylussacia spp. (huckleberry), and Rubus spp. (blackberry) if applied to shrub-area inventories. We sampled blueberry and huckleberry in mature forest where canopy cover and shrub area were constant, and blackberry—a “pioneer” shrub—in shelterwood harvests where light availability decreased with stand development. Annual average (±SE) blueberry SFC (fruits/m2 shrub area) varied from 1.3 ± 0.9 to 18.8 ± 15.8; long-term (11-yr average) SFC (95% CIs) was 6.8 ± 1.8 (3.2–10.3). Annual average huckleberry SFC varied from 1.8 ± 1.3 to 19.8 ± 10.8; long-term average SFC was 11.6 ± 1.8 (8.0–15.3). In shelterwoods, blackberry shrub area and (disproportionately) SFC increased, peaked 3–6 years post-harvest, then declined with canopy closure. When only peak years were included, average blackberry SFC was 90.3 ± 11.3 (67.7–113.0) and is a more reliable estimate for high-light environments. Our SFCs cannot reliably predict crop sizes within any given year or area but provide a forest planning tool to estimate average (over the long-term) or potential fruit production that can be tailored to specific stands and landscapes by application to shrub-area inventories.

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