Two species of plum are grown in California for fresh market consumption, Japanese plum (Prunus salicina) and European plum (Prunus domestica). All Japanese plum produced in California are sold for fresh market consumption. Only 2-3% of European plums* are sold as “sugar plums” for fresh markets, and the rest are dried as prunes (Day and Buchner 2012). Japanese plum (Prunus salicina) originated in China and was domesticated in Japan about 400 years ago. United States commercial cultivation began in the 1870’s in California (LaRue 1973). Currently, ninety five percent of domestic fresh plums are grown in California. In 2014, 105,000 tons were produced on 20,000 California acres, a crop valued at $68,475,000. (Note: this does not include 50,000 acres of prunes.) Most plum production occurs in Tulare and Fresno counties within the San Joaquin Valley. Most plum production occurs in Tulare and Fresno counties within the San Joaquin Valley (USDA 2014).
Plum trees thrive in California’s Mediterranean climate with mild winters and hot, dry summers. Trees grow best in deep sandy loam soils with good drainage, but are tolerant of a wide range of soils. Plum flowers are morphologically similar to peach (perigynous anatomy) with white petals and smaller size (Rieger no date). Flowers and fruit are borne laterally on spurs, although a small number of flowers may be produced laterally on long shoots (see Pollination section for more information). These fruiting spurs live longer than almonds but not as long as apple spurs. For the details of flower anatomy, see Flower Anatomy & Pollination (under Orchard Management), in particular, the Summary Chart: Floral Biology & Pollination.
Plum fruit require 140 to 170 days. The earliest varieties are picked in mid May which is only about 75 days from flowering (early March). Later varieties don’t mature until late September or early October which is about 210 days from flowering to maturation (Vossen and Silver no date). Fruit are typically harvested from May to October in California. Mature plums have an epicuticular wax (dusty whitish coating) known as “wax bloom” that can be rubbed off (Stein et al. no date).