Serenoa repens, commonly known as saw palmetto, is the sole species currently classified in the genus Serenoa. It has been known by a number of synonyms, including Sabal serrulatum, under which name it still often appears in alternative medicine. It is a small palm, normally reaching a height of around 2–4 m (3–6 ft). Its trunk is sprawling, and it grows in clumps or dense thickets in sandy coastal lands or as undergrowth in pine woods or hardwood hammocks. Erect stems or trunks are rarely produced but are found in some populations. It is endemic to the southeastern United States, most commonly along the Atlantic and Gulf Coastal plains, but also as far inland as southern Arkansas. It is a hearty plant; extremely slow growing, and long lived, with some plants, especially in Florida where it is known as simply the palmetto, possibly being as old as 500–700 years. Saw palmetto is a fan palm, with the leaves that have a bare petiole terminating in a rounded fan of about 20 leaflets. The petiole is armed with fine, sharp teeth or spines that give the species its common name. The teeth or spines are easily capable of breaking the skin, and protection should be worn when working around a Saw Palmetto. The leaves are light green inland, and silvery-white in coastal regions. The leaves are 1–2 m in length, the leaflets 50–100 cm long. They are similar to the leaves of the palmettos of genus Sabal. The flowers are yellowish-white, about 5 mm across, produced in dense compound panicles up to 60 cm long. The fruit is a large reddish-black drupe and is an important food source for wildlife and historically for humans. The plant is used as a food plant by the larvae of some Lepidoptera species such as Batrachedra decoctor, which feeds exclusively on the plant. This plant is also edible to human beings, but the more green it is the more bitter tasting it would be.
The fruits of the saw palmetto are highly enriched with fatty acids and phytosterols, and extracts of the fruits have been the subject of intensive research for the symptomatic treatment of benign prostatic hyperplasia (BPH). This extract is also commonly used for other medical conditions, such as baldness, polycystic ovarian syndrome, and other hyperandrogen conditions, though research on such uses is preliminary at best. Numerous meta-analyses of clinical trials S. repens extract in the treatment of BPH have found it safe and effective for mild-to-moderate BPH compared to placebo, finasteride, and tamsulosin Two larger trials found the extract no different from placebo. An updated meta-analysis including these trials found that saw palmetto extract "was not more effective than placebo for treatment of urinary symptoms consistent with BPH". However, saw palmetto extract was comparable to tamsulosin and finasteride in this meta-analysis. Longer-term (2 years; most clinical trials have been 1 yr) open studies suggest that saw palmetto reduces the risk of men with BPH ultimately needing to have surgery.