Current Research

In 1996 University of Florida researchers started a three-year study on saw palmetto. The research focuses on the biological and economic feasibility of managing wild saw palmettos for fruit harvesting. This study includes research on the following topics-- (1) management techniques for saw palmetto; (2) economics of harvesting saw palmetto fruits; (3) basic biology of saw palmetto and (4) effects of fruit harvesting on wildlife.

Management Techniques for Saw Palmetto
In this portion of the study UF/IFAS researchers are evaluating management practices, such as controlled burning and fertilizing, that landowners may potentially use to encourage saw palmetto fruiting.

Saw Palmetto and Fire- Saw palmetto occurs in areas where fires, both natural and human-caused, have historically been frequent. Landowners commonly burn rangelands to improve forage for cattle and/or to improve accessibility. Periodic burning of rangelands also may be a useful management technique to promote saw palmetto fruiting, since the plants are extremely resilient to fires, and commonly flower soon after a burn. But it is not known whether the most common season and frequency of burning for private landowners (winter, approximately every 2 - 3 years) is best for optimal saw palmetto fruiting. UF/IFAS researchers are "zeroing in" on the optimal frequency and season for burning through the following two studies:

Effects of Time Since Burning on Flowering and Fruiting in Saw Palmetto-
Researchers are measuring flowering and fruiting in sites that burned during the growing season (April - July) in 1996, 1995, 1994, 1993, 1992, and before 1991. They began data collection in 18 sites (three sites burned in each year) during the late summer of 1996, and will continue to quantify fruiting and flowering in the same sites for two more years. In a previous study conducted during the 1960's, saw palmettos produced the most fruit after at least four years without burning. The current research will test the results of that study. In addition, results from the current research will show whether saw palmettos produce consistent amounts of fruit in sequential years. Below are some preliminary results from the first season of data collection:

• Saw palmettos in sites that burned during the 1996 growing season generally did not fruit by late fall 1996.
• Only saw palmettos over 53 cm (21 in) in height fruited.
• Of saw palmettos over 53 cm tall, plants with taller and wider crowns were more likely to fruit.
• High per-plant fruit yields were more likely to occur in sites in which high proportions of saw palmettos fruited.
• Density of saw palmettos at a site did not seem to influence the proportion of plants fruiting.
• Saw palmetto fruit or berry yields varied widely from site to site, from 21 kg/ha (19 lb/acre) to 1600 kg/ha (1500 lb/acre).
  
  Effects of Burning Season and Burning Frequency on Saw Palmetto Flowering and Fruiting -
  A goal of this research is to determine the best time and frequency of burning that land managers may use to promote saw palmetto fruiting. Without fire, saw palmettos flower from December to March, and produce fruit from April to October. Although saw palmettos often flower after fires at any time of the year, no one has determined whether those flowers go on to produce fruit at any time of the year. In this study, to begin during the spring of 1997, researchers will quantify flowering and fruiting in sites burned during the growing season (March - July) and during the winter (November - February). Half of the sites burned in each season will have a history of frequent burns (burned every 2 - 3 years for the past 15 years), and half will have a history of infrequent burns (burned less often than every 5 years for the last 15 years). This study is designed to answer three main questions: 1. Do saw palmettos in winter-burned sites fruit the following summer? 2. Do saw palmettos in growing season-burned sites flower the following spring, and fruit approximately a year after the burn? 3. Is fruiting reduced in frequently-burned sites?
  
  Fertilizing Saw Palmetto-
  Can fertilizing induce greater fruit yields in saw palmetto? Some people think that fires act as natural "fertilizing agents" by increasing the availability of soil nutrients to plants. Saw palmettos might flower after fires in response to this "fertilization effect." If so, landowners might be able to induce flowering and fruiting in saw palmettos without burning by applying fertilizer to the soil. However, very limited studies of effects of fertilization on saw palmettos have demonstrated neither a flowering nor a fruiting "response." In the current study researchers are testing several combinations of soil nutrients at a set concentration, to determine if and when saw palmettos respond by flowering and fruiting. Researchers will compare flowering and fruiting among fertilized palmettos, palmettos with leaves clipped (similar to leaves being burned off by fire), and control (untreated) palmettos. Cost of fertilization also will be taken into account, to determine whether fertilizing saw palmetto is an economically feasible management technique for landowners.

Economics of Harvesting Saw Palmetto Fruits
During the 1996 saw palmetto fruiting season, UF/IFAS researchers began monitoring selling prices for saw palmetto berries on the open market, and contract prices paid by buyers to landowners. The selling price on the open market averaged $.12/lb. Saw palmetto berry buyers paid a "delivered-in" price that was a minimum of $.12 - $.13/lb over the open market price to landowners under contract for harvesting berries.

Basic Biology of Saw Palmetto
In order to understand and predict responses of saw palmettos to management practices such as burning and fertilizing, researchers and land managers must know something about the basic biology of saw palmetto. In particular, they must understand the biology of flowering and fruiting. In addition to directly evaluating the effects of management practices on saw palmettos, UF/IFAS researchers are observing flowering and fruiting for a number of marked plants. The researchers will identify insects that fertilize the flowers, and determine what time of the year most flower fertilization occurs. They also will identify pests and diseases that may reduce fruit yields. Lastly, they hope to understand more about factors within a saw palmetto plant that may "trigger" flowering. Results from previous studies have suggested that flowering occurs when large amounts of stored carbohydrates are present in the stem. UF/IFAS researchers plan to (1) quantify stored carbohydrate levels in flowering and nonflowering plants; and (2) determine if and how management practices influence levels of stored carbohydrates in saw palmettos.

Effects of Fruit Harvesting on Wildlife
Saw palmettos are certainly a conspicuous part of the landscape in some natural communities, and are a significant source of food and shelter for several wildlife species. Indiscriminate harvesting of saw palmetto fruits could adversely affect some wildlife species, especially when market prices for saw palmetto berries are high, wildlife population levels are low, and/or saw palmetto berries are an essential food source for a species. The current research will focus on the potential impact of fruit harvesting on the black bear, a threatened species in Florida. Black bears range over wide areas, and sometimes eat saw palmetto berries almost exclusively during the late summer and fall. Bears have reportedly shifted their home ranges during saw palmetto fruiting season to take advantage of the abundant food available. Researchers will identify extent of fruit harvesting in areas used by black bears, and will determine if areas of light or no harvesting should be recommended.

For more information about current saw palmetto research at the University of Florida contact Dr. Jeff Mullahey at the Southwest Florida Research and Education Center.

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