Plum Varieties are Complex and Fascinating [Slideshow]

Plums offer a huge array of colors, textures, and flavors, and compared to other tree fruit, can be confusing to growers, marketers, and consumers. Plum variety sizes range from marble to baseball, shapes range from round, oval, heart-shaped, to torpedo, and textures from crunchy to soft. In contrast to peaches which is the single species, Prunus persica, plums consist of four different species Prunus domestica (European), P. americana (American plum), P. cerasifera (cherry plum), and P. salicina (Japanese plum) plus their hybrids.

This diversity of varieties makes plums both interesting and challenging for growers and marketers. European plum varieties are generally restricted to more northern growing areas due to problems with tree mortality in southern areas. Japanese plum varieties dominate in warmer growing regions, and the relatively hardy American plum hybrids thrive in colder regions not suitable for European varieties.

Buying Plums By Appearance
Customers, even avid fans of plums, tend to remember and seek out their favorites by shape, skin, and flesh color rather than by name. It is, for example, the “heart-shaped dark red plum with dark red flesh,” or the “late variety with red skin and amber flesh” they remember, rather than ‘Duarte’ or ‘Alderman.’ Customers of red-skinned varieties are helped by memorable names such as ‘Elephant Heart,’ ‘Redheart,’ ‘Oxheart,’ ‘Ruby Sweet,’ and ‘Ruby Queen,’ but keeping the varieties straight is still a challenge.

A challenge for Eastern U.S. plum growers is the lack of a series of similar appearing plum varieties to stretch across the growing season. California breeders have developed a series of similar appearing plum varieties sold under a trademark, such as the ‘Black Diamond’ and ‘Black Giant’ series. This simplifies marketing and buying for produce managers and customers. Customers can come back to the store and buy a similar looking piece of fruit, even though in actuality it is a different variety. These displays are not marked with the plum variety name.

This is the beauty of marketing under a trademark — simplicity for the produce manager and the customer. Unfortunately, most of the varieties developed in California for the chain store market are not suited for the humidity nor the cool climate of the middle to upper Eastern U.S.

The Blue Line
Probably the closest to a series for Northern plum producers is the blue European prune plum group, including ‘Valerie,’ ‘Vanette,’ ‘Castleton,’ ‘NY9,’ ‘Bluebyrd,’ ‘Stanley,’ ‘Victory,’ and many others, but even this group’s members range from small to large, oval to elongated, and various shades of blue. Even flavor — the varieties ‘DeMonfort,’ ‘Italian,’ ‘Mont Royal,’ and ‘Vision’ in this broad group often get the nod for being the most flavorful for their combination of sweet/tart balance. Work by the plum breeding programs at Cornell University and Harrow/Vineland, Ontario, now discontinued, did much to develop blue prune/plum varieties for the whole season.

A few, like ‘Stanley’ and ‘Italian,’ have wide name recognition, and a few have strong connections with ethnic groups such as the ‘Dunkelburg’ plum, a round, somewhat small, blue prune plum of German origin, and the ‘Damson’ plum that is excellent for jams and famous for plum brandy. ‘Damsons,’ being clingstone and somewhat astringent, are best suited for processing.

There are other unique subgroups of plum varieties such as the partially to wholly yellow skin group including ‘Ohishi Washi,’ ‘Early Golden,’ ‘Yellow Egg,’ ‘Shiro,’ and ‘Luisa.’ This is an attractive group adding color and contrast to a plum display, but cannot be considered a series.

The Crunch Factor
Like the ‘Honeycrisp’ and ‘EverCrisp’ apple varieties, plums can have their own type of crunch factor. The firm texture of a fresh plum with a good sweet/acid balance is a wonderful eating experience. But delivering consistent quality can be a challenge for some varieties. The old European variety ‘Stanley’ is a prime example of a variety with a nice texture and flavor when picked at the optimum time, but goes from firm and ripe to soft and overripe rather quickly.

There is some evidence that preharvest application of the growth regulator ReTain (active ingredient: AVG, Valent USA) to plum will help preserve fruit firmness, much like in other stone fruit and pome fruit, but is not yet an established practice.

Good Things in a Small Package
The ‘Mirabelle,’ ‘Gage,’ and ‘Santa Rosa’ group represents a completely different eating experience —small, very sweet, and some with soft texture and aromatic qualities. The ‘Mirabelle’ group wins fans with their soft, sweet, and aromatic tastes — generally too soft for U-pick, but well suited for direct market gourmet customers. ‘Gages’ are small, very sweet, but unlike the ‘Mirabelle’ group, generally have a crisp eating texture. ‘Santa Rosas’ are juicy with slightly firm flesh and more suited for cooking with a sweet/tart flavor. And for something different, there’s the petite, somewhat odd ‘Toka’ plum with a bubblegum-like flavor and soft texture.

Plums are an odd collection of varieties but offer rewards to growers and customers who take the time to learn about them.

For further information on plum varieties visit the Michigan Plum Growers Advisory Group’s website.

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