Prunes are made from European plums (Prunus domestica), a species with dense flesh and high sugar content that allows the fruit to dry without fermenting or falling apart. Not every plum can become a prune. The varieties that work share a specific set of traits: firm texture, thick skin, and enough natural sugar to preserve the fruit through dehydration.
European Plums vs. Japanese Plums
The plum world splits into two major groups, and only one is suited to prune-making. European plums are smaller, oval or egg-shaped, and have a firm, dense flesh. Japanese plums (Prunus salicina), the round, juicy ones you typically find in grocery store produce sections, are larger and much more watery. That juiciness is great for eating fresh but terrible for drying. The high moisture and soft flesh of Japanese plums cause them to collapse and spoil rather than dehydrate cleanly.
European plums hold their shape when dried because of their dense flesh and thick skin. Their higher sugar content acts as a natural preservative during the drying process, concentrating flavor instead of allowing the fruit to rot. This combination of structure and sweetness is what separates a prune plum from a fresh-eating plum.
The Varieties That Become Prunes
A handful of specific European plum cultivars dominate commercial prune production. The most important is the French Improved (also called Improved French or d’Agen), which produces the vast majority of prunes sold in the United States. It’s an egg-shaped plum with deep purple-to-black skin and amber-gold flesh. It ripens in late summer, typically August through September, and thrives in zones 5 through 9 with around 800 chill hours. The flavor is intensely sweet, which makes it ideal for drying.
The Stanley plum is another widely grown prune variety, particularly popular among home growers in the eastern U.S. and Great Lakes region. It’s a reliable, self-fertile tree that produces dark purple, freestone plums well-suited for both drying and canning. Other cultivars used for prunes include Bluefire and various regional European selections, though these are far less common in commercial production.
In France, the same d’Agen plum variety has been used for centuries to make “Pruneaux d’Agen,” which earned a Protected Geographical Indication from the European Union in 2002. That designation means only prunes grown and processed in specific French regions under defined standards can carry the name.
Where Prune Plums Grow
California produces nearly all of the commercial prunes in the United States, centered in the Sacramento and San Joaquin Valleys. The hot, dry summers provide ideal conditions for both growing and sun-drying the fruit. The West Coast and Great Lakes regions are the primary growing areas for Prunus domestica in the U.S., with the Great Lakes offering the cold winters these trees need to set fruit properly.
France remains the other major prune-producing region globally, with production concentrated in the southwest around the Lot-et-Garonne department, the historical home of the d’Agen prune.
How Plums Become Prunes
The drying process is straightforward but precise. Commercially, fresh plums are dehydrated at around 85 to 90 degrees Celsius (roughly 185 to 195°F) for about 18 hours. Some producers start at a higher temperature and then drop to around 70°C once the fruit reaches 50% moisture, which helps preserve more of the beneficial plant compounds. The finished prune has lost approximately 80% of its original moisture. A properly dried prune shows no visible moisture, isn’t sticky to the touch, and has a deep, concentrated sweetness.
You can dry prune plums at home using a food dehydrator or a low oven. The key indicators of doneness are the same: the fruit should be pliable but not wet, with no moisture beading on the surface when you squeeze it.
What Changes When a Plum Dries
Drying concentrates everything in the fruit. By weight, prunes are significantly higher in calories, fiber, and carbohydrates than fresh plums. A serving of four to six prunes (about 40 grams) contains around 100 calories and 3 grams of fiber, which is 11% of the daily recommended value. That same weight of fresh plum would have fewer calories and less fiber simply because so much of a fresh plum is water.
Prunes also contain sorbitol, a sugar alcohol with natural laxative effects. This compound, combined with the concentrated fiber, is why prunes have their well-known reputation for supporting digestion. The drying process also increases the concentration of phenolic compounds, a group of antioxidants. Prunes actually contain higher levels of these compounds than most other commonly eaten fruits.
What to Look for If You’re Growing Your Own
If you want to grow plums specifically for making prunes, choose a European variety labeled as a “prune plum” or “freestone” type. The French Improved and Stanley are the most accessible options at most nurseries. Look for fruit that is egg-shaped rather than round, with firm flesh that doesn’t squish easily. When ripe, the plums should detach from the branch without much effort and feel dense in your hand rather than soft and yielding.
Greengage and damson plums are both subspecies of Prunus domestica, but they serve different purposes. Greengages are prized for fresh eating, and damsons are typically used for jams and preserves. Neither is a good candidate for prune-making because they lack the ideal sugar-to-moisture ratio of true prune cultivars. Stick with varieties specifically bred for drying if prunes are your goal.