Prunus domestica, the plum tree, offers home gardeners fresh, flavorful fruit. These deciduous trees produce abundant harvests with consistent care. Understanding their specific needs, from planting to annual maintenance and harvesting, leads to a productive and healthy orchard. This guide provides insights into cultivating successful plum trees.
Choosing and Planting Your Plum Tree
Selecting a Variety
Choosing the right plum variety is key for a bountiful harvest. Varieties differ in chilling hour requirements, the cold exposure needed to break dormancy and flower. European plums (e.g., ‘Victoria’, ‘Green Gage’) are hardier and adapt to diverse climates. Many European types are self-fertile, though cross-pollination often enhances yields. Japanese plums (e.g., ‘Santa Rosa’, ‘Satsuma’) thrive in warmer regions, but their early blooms are susceptible to late spring frosts. Japanese varieties typically require cross-pollination, necessitating a compatible second tree nearby.
Site Selection
An ideal planting site is crucial for a plum tree’s long-term health and productivity. Plum trees need full sunlight, at least six to eight hours daily, for robust growth, bud initiation, and better fruit ripening. A sheltered location, protected from strong winds, is also beneficial, as winds can damage blossoms and deter pollinators. Avoid low-lying areas where frost settles, especially for early-flowering varieties, as spring frosts can damage blooms and reduce fruit set.
Plums prefer well-drained, fertile soil, ideally a sandy loam, but tolerate other soil types if drainage is adequate. Good drainage prevents waterlogging. An optimal soil pH for plum trees ranges between 6.0 and 6.8, slightly acidic to neutral, ensuring nutrient availability. Incorporating organic compost can improve soil structure and nutrient content, especially in low-fertility or heavy clay soils.
Planting Process
Planting plum trees is best during the dormant season, typically late winter or early spring, before new growth. This timing minimizes transplant shock, allowing the tree to establish roots. Bare-root trees are available only during dormancy, while containerized trees can be planted year-round, though they establish best from late autumn to spring. Soak bare-root trees in water for one to two hours before planting. Water container-grown trees thoroughly before removal.
Dig a planting hole two to three times wider than the root ball and as deep. Loosen the soil at the bottom and mix in compost to enhance root establishment. Position the tree centrally, ensuring the graft union remains one to two inches above the soil line. Backfill with excavated soil, gently firming it to eliminate air pockets. After planting, water deeply to settle the soil. Young trees, especially bare-root ones, benefit from staking for the first few years for stability.
Ongoing Maintenance for Healthy Growth
Watering
Consistent watering is fundamental for plum trees, particularly during establishment and fruit development. Newly planted trees need regular watering in their first growing season for root development, typically about 5 gallons one to three times a week, depending on soil and weather. Established trees generally need about one inch of water per week from rainfall or irrigation.
During dry spells, especially from early to mid-summer when fruits swell, consistent moisture is important. Insufficient water can lead to premature fruit drop. Check soil moisture by inserting a finger or moisture meter; water when the top eight to ten inches feel dry. Deep, infrequent watering is more effective than shallow, frequent applications, encouraging deeper roots and enhancing drought resistance. Apply water directly to the root zone, avoiding foliage, to prevent fungal diseases.
Fertilizing
Adequate nutrients support vigorous growth and abundant fruit production. A soil test before fertilizing helps determine specific deficiencies. For newly planted trees, fertilization can be delayed if soil was amended, or a light application of balanced fertilizer (e.g., 10-10-10) can be applied in early spring. Nitrogen is important for vegetative growth, especially in younger trees.
Established plum trees generally benefit from fertilization once or twice a year. Apply a balanced fertilizer in early spring as leaves bud out. A second application can occur in mid-summer, a few weeks before fruits ripen. For mature trees, apply fertilizer evenly around the base, extending to the drip line, avoiding direct contact with the trunk. Over-fertilization, particularly with excessive nitrogen, can lead to lush vegetative growth at the expense of fruit production and increase susceptibility to winter damage.
Soil Health
Maintaining healthy soil around plum trees is vital. Mulching offers numerous benefits, including moisture retention, weed suppression, and soil temperature moderation. Apply an organic mulch, such as wood chips or well-rotted compost, four to six inches deep, keeping it a few inches away from the trunk to prevent moisture buildup and rot. Mulch also gradually breaks down, enriching the soil and improving its structure.
Plum trees thrive in soils with a pH between 6.0 and 6.8. If a soil test indicates the pH is outside this range, agricultural lime can raise pH, while sulfur or organic compost can lower it. Maintain a weed and grass-free area of at least four feet around the tree to reduce competition for water and nutrients.
Pruning for Productivity and Shape
Why Prune?
Pruning is essential for healthy, productive plum trees. It serves multiple purposes:
Improves air circulation within the canopy, reducing fungal diseases.
Allows better sunlight penetration, promoting even fruit ripening and enhancing quality.
Encourages stronger branches capable of supporting heavy fruit loads, preventing breakage.
Helps maintain the tree at a manageable size and shape.
When to Prune
Timing is crucial when pruning plum trees due to disease susceptibility. Plums are best pruned in early spring for young trees or mid-summer for established ones. Pruning during these periods helps wounds heal quickly, reducing the risk of silver leaf disease, a fungal pathogen affecting Prunus species. Avoid winter pruning, as damp conditions increase the likelihood of silver leaf disease entering cuts. For young trees, light pruning can begin immediately upon planting to establish shape.
How to Prune
Effective pruning involves understanding the tree’s structure and making precise cuts. A common goal is an open-centered or vase shape for optimal light and air penetration.
Remove dead, diseased, or damaged branches cleanly back to healthy wood.
Eliminate branches that cross or rub against each other, as this creates wounds.
Use thinning cuts (removing an entire branch) to open the canopy and improve air circulation.
Use heading cuts (shortening a branch) to control height or encourage bushier growth.
Always use sharp, sterilized pruning tools for clean wounds and to prevent disease transmission.
Make cuts just above an outward-facing bud, sloping away from it, to direct new growth outward.
Remove suckers from the rootstock or lower trunk to maintain vigor and shape.
Protecting Your Plum Tree from Pests and Diseases
Common Pests
Plum trees can be affected by various pests:
Aphids: Small insects that feed on sap, causing leaves to curl and distort.
Plum curculio: A snout beetle whose larvae damage developing fruit, leading to premature fruit drop or scabbing.
Borers: Tunnel into the wood, disrupting nutrient flow and making the tree susceptible to other issues.
Common Diseases
Several diseases can affect plum trees:
Brown rot: A fungus infecting blossoms, fruit, and small branches, causing blight and fruit decay.
Silver leaf disease: A fungal infection causing a silvery sheen on leaves and internal wood discoloration, often entering through pruning wounds.
Bacterial canker: Causes lesions on branches, stunted leaf development, and sometimes a sour-smelling ooze.
Powdery mildew: Appears as a white, powdery coating on leaves and twigs, leading to distorted growth.
Black knot: A fungal disease characterized by hard, black, gall-like swellings on branches.
Plum pox virus: Causes yellow rings on fruit and leaves, significantly reducing quality and yield, often spread by aphids.
Integrated Pest Management
An integrated pest management (IPM) approach effectively manages plum tree pests and diseases, focusing on prevention and minimal intervention.
Select disease-resistant varieties when available.
Practice good sanitation: regularly clean up fallen leaves and fruit to reduce overwintering sites for pests and disease spores.
Utilize proper pruning techniques to improve air circulation and remove infected material promptly.
Monitor trees regularly for early signs of pests or diseases for timely interventions.
Encourage beneficial insects like ladybugs for aphid control.
Consider organic sprays, such as dormant oil applications or copper-based fungicides, for prevention or early-stage infections. Consult local cooperative extension services for specific recommendations.
Harvesting and Preparing for Winter
When to Harvest
Plums are generally ready for picking between July and September, depending on the variety. Cues for ripeness include:
Visual: A deep, vibrant color uniform across the skin, characteristic of the variety. A powdery coating (bloom) indicates the fruit has not been overhandled.
Tactile: The plum feels soft and yields slightly to gentle pressure but is not mushy. Unripe plums feel firm.
Olfactory: A sweet, fruity aroma, particularly near the stem and blossom ends.
Detachment: Plums detach easily from the branch with a gentle twist or upward push. If significant pulling is required, they need more time.
Since plums on a single tree often ripen at different rates, multiple harvesting passes may be necessary over a two-week period.
How to Harvest
Gentle hand-picking is the preferred method. Grasp the plum gently and twist or push it upwards from the stem attachment point. The goal is to remove the fruit without tearing the skin or pulling the stem out, which can create an open wound. For out-of-reach plums, a pole picker can be used for firmer fruits. For larger quantities, a “shake and catch” method, shaking branches over a tarp, can be employed, as usually only riper fruit will fall.
Winter Preparation
Preparing the plum tree for winter dormancy is essential for its survival and future productivity. Provide a final deep watering before the ground freezes, especially if autumn has been dry, to ensure adequate moisture reserves. Apply a fresh layer of organic mulch around the base of the tree, extending to the drip line, to insulate roots and retain moisture. For young trees, especially in harsh winters or areas with significant pest pressure, protecting the trunk with a tree guard can prevent damage from rodents or deer.