Site Selection and Planting
- Choose a site that is in full sun. Plums and Prunes are tolerant of many soil types, but will perform best on deep, well-drained soil.
- Check pollination requirements. Japanese plums will not pollinate European plums or vice versa as they bloom 2-3 weeks apart. Some plums are partially self-fertile; those will produce more as young trees if planted with a pollinizer. Fully self-fertile plums can be planted alone.
- Because plum and prune trees bloom early, a site that does not get late frosts is best. Frequent frost during and after bloom will mean poor fruit set.
- Keep grass and weeds away from the tree to reduce competition. A very thin mulch can be used to keep weeds down.
- Irrigate thoroughly during the summer months, watering infrequently but deeply. It is especially important to water adequately while the fruit is approaching ripeness.
- Remember the goal in the home orchard is to keep the trees healthy.
- Plums and Prunes benefit from a delayed dormant spray of copper sulfate and oil, applied at stage 3 of bud swell when the bud scales have separated but are not yet showing petal color.
- During the spring and summer months, watch for aphids, and control with horticultural soap or a strong jet of water.
- If you have had Brown Rot (fruit rotting from the blossom end as it approaches ripe), spray copper at leaf fall, and again at stage 3 the following spring. Remove dropped fruit from the orchard and dispose of. A fall spray of copper can also help prevent Bacterial Canker.
- Black Knot (warty black growths on the twigs) can be a problem of plum and prune trees. It is spread by wind from other diseased trees. If possible, remove diseased trees from the surrounding areas. If black knot appears on your trees, spray sulfur at blossom petal fall. Remove any knots that appear by cutting below the growths during dry periods in the spring to remove them– destroy this wood.
- At planting, choose 3-4 evenly spaced branches to form the main trunks, or leaders. It is best to choose branches that are not too upright. Ideally the branch angle should be about 30°-45° (90° is horizontal, 0° is vertical). Remove all other branches, and cut these trunks back to 18″-24″.
- The first summer, after 12″ of new growth, pinch all but two shoots from each branch.
- In the following years, remove broken or crossing branches during the winter season. Thin branches to maintain light penetration and reduce crowding.
- Keep the height of the tree in check by cutting back main branches to a non- fruiting lateral branch, during the dormant season.
- In summer, remove water sprouts and suckers. Cut out any black knot.
Plums and prunes can have alternate years of light crops and heavy crops. During light crop years, it can be beneficial to pinch back or prune sprouts and suckers more vigorously as the tree is not spending as much energy producing fruit. In heavy crop years, it might be necessary to hand thin the fruit after set. Fruit that is crowded and touching is more subject to brown rot. It is also sometimes necessary to support branches that have heavy fruit loads.