Plum trees (European Prunus domestica and Japanese Prunus salicina) offer a rewarding harvest. Known for their spring blossoms and flavorful summer fruit, these trees require specific attention to thrive and produce consistently. Success depends on careful preparation, routine maintenance, and timely intervention.
Site Selection and Initial Planting
The optimal planting location requires full sun exposure (at least six to eight hours daily). Consistent light is necessary for vigorous growth and fruit development. Plum trees prefer well-drained, loamy soil and do not tolerate standing water, which causes root rot.
The ideal soil pH ranges from slightly acidic to neutral (6.0 to 7.0). When planting, dig a hole twice as wide as the root ball but no deeper, ensuring the graft union remains two to four inches above the final soil line. Backfill the hole with the original soil, tamping gently to remove air pockets, and water thoroughly to help the roots settle.
Ongoing Watering and Feeding Requirements
Consistent moisture is important for newly planted trees, requiring regular watering during the first two seasons for deep root establishment. Deep watering once a week, rather than shallow sprinklings, promotes a drought-resistant root system. Mature trees tolerate dry conditions but benefit from deep irrigation during prolonged dry spells when fruit is developing.
Fertilization supports tree health and fruit production, though established plums are not heavy feeders. A balanced fertilizer (e.g., 10-10-10) should be applied to mature trees in early spring before new growth begins. Young trees benefit from a nitrogen-rich fertilizer in their first year, but high-nitrogen applications should be reduced later to avoid excessive foliage. Organic mulch (wood chips or straw) helps retain moisture, stabilize temperature, and suppress weeds. Keep mulch several inches away from the trunk to prevent fungal issues.
Mastering Pruning Techniques
Pruning maintains structural integrity, improves air circulation, and maximizes fruit yield. Timing is important, as dormant winter cuts can increase susceptibility to silver leaf, a fungal disease. Major structural pruning is reserved for late winter or early spring just before bud break, or during the mid-summer months.
Dormant Pruning
Dormant pruning, performed in late winter, focuses on shaping the tree, removing dead or damaged wood, and thinning crowded branches to create an open center or central leader structure. This stimulates vigorous new growth, which establishes a strong framework in young trees. Cuts should be made cleanly just above an outward-facing bud to direct new growth away from the canopy center.
Summer Pruning and Thinning
Summer pruning, conducted between mid-June and August, is a lighter process aimed at controlling the tree’s size and vigor. This is the safest time to remove water sprouts and suckers emerging from the base or roots. Summer cuts ensure light penetrates the canopy for fruit ripening and reduce humid conditions that favor fungal diseases. Fruit thinning involves removing small plums to leave four to six inches between remaining fruits. This prevents branches from breaking and increases the size and quality of the final harvest.
Managing Pests and Diseases
Plum trees are susceptible to several pests and diseases requiring proactive management. One destructive fungal infection is brown rot (Monilinia fructicola), which attacks blossoms, twigs, and fruit. Infections are characterized by shriveled, brown flowers and fruit developing soft, expanding spots covered with grayish mold.
Brown rot management relies on sanitation, including removing all fallen and mummified fruit that harbors the fungus over winter. Regular pruning increases air circulation, reducing humidity that promotes fungal growth. For chemical control, organic options like copper-based sprays or sulfur can be applied during the bloom period and repeated during wet weather.
Plum curculio is a common insect pest, a small weevil that damages developing fruit by laying eggs, leaving crescent-shaped scars and causing premature fruit drop. Control involves collecting and destroying fallen fruit to interrupt the insect’s life cycle. Aphids are also frequent visitors, controlled by encouraging natural predators or using targeted applications of insecticidal soap or neem oil early in the season.
Knowing When and How to Harvest
Determining the ideal harvest time depends on the specific variety; Japanese types (Prunus salicina) ripen in mid-to-late summer, while European plums (Prunus domestica) may not be ready until early fall. Reliable indicators of ripeness are a change in color, a slight softening of the flesh, and the ease with which the fruit separates from the branch.
A ripe plum should yield slightly when pressed gently but should not feel mushy. For the best flavor, plums should ripen fully on the tree, coming away with a gentle twist. Harvest carefully to avoid bruising the fruit, ideally picking in the cooler morning hours to preserve freshness. Slightly firm plums can be picked and allowed to finish ripening off the tree, but they will lack the full sugar content of tree-ripened fruit.