Japanese Plum
Mariposa plum is a heirloom cultivar selected by Jennie Benedict Thompson in 1923 from a chance seedling discovered in Pasadena, California. This low-chill plum thrives in zones 6-10 and reaches 12 to 16 feet at maturity, producing large heart-shaped fruit with glossy green skin mottled deep maroon and vibrant red flesh surrounding a small, nearly freestone pit. The sweet, aromatic flavor carries a pleasantly tart skin, making it excellent for both fresh eating and cooking. Its low chill requirement makes it especially valuable for gardeners in milder climates where traditional plums struggle.
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6-10
192in H x ?in W
Perennial
High
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Mariposa plums are large, juicy fruits with a distinctive heart shape and mottled maroon-over-green skin that deepens as they ripen. The nearly freestone pit, small compared to the plum's size, makes eating fresh effortless, while the firm flesh holds up beautifully when cooked into sauces or preserves. Because it needs very few chill hours to set fruit, Mariposa performs where other plums fail, opening possibilities for gardeners in warm and mild-winter regions who assumed plums were off-limits.
Mariposa plums excel at the table as fresh fruit, their juicy sweetness and manageable freestone pit making them a pleasure to eat out of hand. The firm flesh and balanced sugar-acid profile also make them outstanding for cooking, breaking down beautifully into jams, sauces, and preserves while holding their color and flavor complexity. They can be trained as espaliers on warm, south-facing walls, combining ornamental value with productivity in small-space gardens.
Plant bare-root or container-grown Mariposa plum trees in late winter to early spring, or in fall in mild-winter regions. Space trees 12 to 16 feet apart to accommodate mature size. Choose a location with full sun exposure and well-drained soil. Dig a hole slightly wider than the root ball and at the same depth as it was growing in the nursery pot or field. Backfill with native soil and water deeply to settle the soil.
Mariposa plums mature in late summer, typically reaching harvest readiness from late July through early September depending on your zone and spring warmth. Pick fruit when the skin has developed its full deep maroon color and the plum yields slightly to gentle pressure, signaling peak ripeness and juiciness. The small pit detaches cleanly from the flesh at full maturity, making harvest straightforward. Plums can ripen slightly after picking if harvested at the firm-ripe stage, though they develop maximum flavor when left on the tree until fully soft.
Prune Mariposa plum lightly to maintain an open, spreading canopy that encourages even ripening and good air circulation. Remove any crossing or inward-growing branches, and thin the canopy in late winter before bloom begins. If training as an espalier, begin shaping young trees early, establishing the horizontal framework and tying branches to supports as they grow. Avoid heavy pruning, which can reduce fruit production in subsequent seasons.
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“Mariposa plum emerged by chance in 1923 when Jennie Benedict Thompson discovered a seedling growing in her Pasadena, California garden. Rather than letting this exceptional tree fade into obscurity, Thompson selected and propagated it, preserving what would become a cornerstone variety for low-chill plum cultivation in California and beyond. The variety's alternative name, Improved Satsuma, reflects its lineage and refinement over time. This human-driven selection transformed a single fortunate discovery into a heirloom now available to home gardeners, carrying forward Thompson's legacy of careful observation and horticultural intuition.”