Jam Session is a heavily productive European plum released by Cornell University that transforms September harvests into deeply flavored preserves and sauces. This small freestone plum bears bright blue skin with greenish-yellow flesh and delivers a rich, Damson-style character that's less astringent than its sister variety Blues Jam. Hardy in zones 5 through 9 and reaching 12 feet at maturity, it thrives in full sun and rewards gardeners with thousands of ripe fruit ready for jam-making in mid-September.
Full Sun
Moderate
5-9
144in H x ?in W
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High
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Cornell bred this plum specifically for preserving, and the results shine in every jar. The tree becomes a spectacular sight in September, literally loaded with small blue fruit that beg to be turned into sauce or chutney. Its freestone pit separates cleanly from the flesh, making processing simpler than clingstone varieties. The flavor leans toward that classic Damson intensity without overwhelming bitterness, striking a balance that makes it superior to some of its relatives for serious jam makers.
This plum exists almost entirely in the kitchen. It excels at jam and preserve making, where its rich flavor and lower astringency create complex, deeply satisfying results. Tarts and chutneys benefit equally from its concentrated taste and natural acidity. Fresh eating is secondary; gardeners grow Jam Session knowing their harvest will become pantry staples rather than dessert plates.
No timeline data available yet for this variety.
Plant bare-root trees in early spring before bud break, or container trees in spring or fall. Set the graft union (if present) about two inches above soil level. Space trees 12 to 15 feet apart in full sun. Water thoroughly after planting and maintain consistent moisture through the first season.
Pick Jam Session plums in mid-September when the skin is fully bright blue and the fruit yields slightly to gentle finger pressure but before it becomes soft. The small size means harvesting happens quickly once the tree reaches peak ripeness. For jam making, slightly underripe fruit with good acidity produces superior results; fully ripe fruit is softer and may yield less structured preserves. Harvest frequently as fruit ripens to prevent overripeness and splitting.
Prune in late winter while dormant to establish an open center or vase-shaped framework that allows light into the tree's interior and encourages the heavy fruit production Jam Session is known for. Remove crossing branches, dead wood, and any growth that crowds the canopy. This variety responds well to moderate pruning; don't shy away from cutting back aggressive growth to redirect energy toward fruit rather than wood.
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“Jam Session emerged from Cornell University's breeding program, developed by crossing an open-pollinated parent with Late Muscatel to create a plum optimized for kitchen use rather than fresh eating. Also known as NY 111, this cultivar represents the deliberate work of researchers who recognized that home preservers and small-scale producers needed varieties bred with their specific needs in mind. The emphasis on heavy productivity and consistent fruit quality reflects a shift toward functional fruit breeding, where flavor and processing characteristics drive the work as much as yield.”