Saw Palmetto (Serenoa repens) Flowering and Fruiting Response to Time Since Fire

Mary E. Carrington, J. Jeffrey Mullahey

Abstract


Saw palmetto (Serenoa repens [Bartr.] Small) is a shrubby palm common in southeastern US pine flatwoods ecosystems. Demand
recently has increased for fruits for the herbal remedies market. Because only wild saw palmettos are harvested, management
strategies are needed to promote flowering and fruiting. This study investigated effects of time since growing season (April–July)
fires on flowering and fruiting of saw palmetto ramets54 cm in height, in 18 pine flatwoods or dry prairie sites (six sites in
three locations, burned in 1996, 1995, 1994, 1993, 1992, or before 1991) in central and southwest Florida from 1996 to 1999.
We used repeated measures, linear mixed models to test for time since fire effects on proportion of ramets flowering, proportion
of ramets fruiting, and fruit yield. Ranges of means among sites over all years of the study for proportion of ramets flowering,
proportion of ramets fruiting, and fruit yield were 0 to 0.78, 0 to 0.72, and 0 kg ha1 to 2 869 kg ha1, respectively. Time since
fire strongly influenced flowering; highest probability of flowering occurred 1 yr after burning, followed by an abrupt decrease 2
yr after burning, then a gradual increase from 3 to 5 yr after fires (polynomial regression, P,0.0001 for fixed effects).
Probability of fruiting increased with increasing time since fire (quadratic regression, P,0.001 for fixed effects), but fruit yields
showed no pattern in response to time since fire (P¼0.916). The decrease in influence of fire from flowering through fruit
maturity presumably was caused by mortality from factors such as caterpillar predation and fungal infection. To promote
increased flowering and fruit yields, we recommend that growing season burns be conducted approximately every 5 yr. We
suggest, however, that management strategy be modified as necessary to maintain ecosystem diversity and function.

Key Words: ecosystem management, fire, flatwoods, Florida, forest management, plant ecology


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