The plum season varies depending on the country and climate in which they are grown, but can encompass a span anywhere from mid-May to early October. There are over 2,000 different varieties of plum trees, with 100 of these commonly grown in the United States and 50 of those in northern California. Plums are also grown commercially in the UK, Australia, Guyana, and elsewhere. The main plum season for the most widely sold varieties is summer, with August being the peak period for them in the UK, and autumn, in general, in Australia.
Categories of plum trees are usually narrowed down to six varieties: Japanese, American, Damson, Ornamental, Wild, and European or garden plums. The Japanese plum season runs from May to August, while the European varieties mature in the latter half of the year. Since there are so many varieties of plums and so many places where they are grown, they are usually available throughout the entire spring to fall growing season in one form or another.
European plums originated in the region of Europe near the Caspian sea, and over 300 varieties were already being cultivated by the time of the Roman empire over 1,500 years ago. Pilgrims carried these varieties to the US in the early 17th century, where 90% of plums were grown in California. The cooler climates of New England, the Midwest, and also Canada produce varieties with a early plum season as compared to California.
Japanese plums originated in China, but were more intensively cultivated in Japan. These varieties were also introduced to US growers in the 19th century. A Japanese plum has a dark red to purple color when mature and will often have a dusty white-blue coating on the surface of the skin that is referred to as wax bloom. They are considered a spring fruit, and are one of the most widely sold varieties at the start of the plum season.
Seasonal plums can be further broken down by individual strains. The earliest varieties are Beauts, such as Red Beaut and Black Beaut, which mature in mid- to late May. Mid-season plums include the Queen Rosa and El Dorado, as well as the Laroda and Simka strains, and the Santa Rose and Black Amber strains, which mature from the middle of June to the middle of July. Friar plums also mature in July and are available throughout the fall. The strains that mature the latest in the plum season are Kelsey, Casselman, and Angeleno. Angelenos mature later than any other variety, and are shipped to markets throughout late November.
Cooking with plums in the UK often involves the Merryweather Damson variety, which is suitable for making plum jam or gin. The Warwickshire Drooper is also considered a good plum for cooking purposes or making jam and jelly preserves. Green Gage varieties of plums are widely used in both the US and UK for making jam when they mature in August. Some common varieties such as the Santa Rosa also have French and Italian strains that are largely targeted towards the making of prunes throughout the season.
Plums can range in color from purple to yellow and green, and, since some are picked unripe, a plum season can vary considerably based on how far the fruit is allowed to mature. The Persian Green is an example that is grown in the US and the mountains of Iran, and is a small, pale-green variety that is picked early when it is unripe and eaten with salt. Some plums such as the Elephant Heart, which is a large heart-shaped plum with dark purple skin and red markings, are allowed to mature fully. The Elephant Heart is considered so delicious that it has been compared to the taste of red wine.