Most prunes are freestone cultivars (the pit is easy to remove), whereas most other plums grown for fresh consumption are clingstone (the pit is more difficult to remove).
More than 1,000 plum cultivars are grown for drying. The main cultivar grown in the United States is the Improved French prune. Other varieties include Sutter, Tulare Giant, Moyer, Imperial, Italian, and Greengage. Fresh prunes reach the market earlier than fresh plums and are usually smaller in size.
In 2001, plum growers in the United States were authorised by the government to call prunes "dried plums". Due to the popular U.S. perception of prunes being used only for relief of constipation, and being the subject of related joking, many distributors stopped using the word "prune" on packaging labels in favour of "dried plums".
Prunes contain dietary fiber (about 7% per gram; table) which may provide laxative effects, a conclusion reached in a 2012 review by the European Food Safety Authority demonstrating that prunes effectively contribute to the restoration of normal bowel function in the general population if consumed in quantities of at least 100 grams (3.5 oz) per day.
Prunes are 31% water, 64% carbohydrates, including 7% dietary fiber, 2% protein, and less than 1% fat (table). Prunes are a rich source of vitamin K (57% of the Daily Value, DV) and a moderate source of several B vitamin and dietary minerals (10-16% DV; table).