Growing
Watering
- Be sure to water the young trees heavily every week during the first growing season to help promote growth. Then, water regularly. It’s best to water the plant deeply at the soil line, then let the soil dry out (though not completely) and water again.
- If rain is lacking, water your tree well into mid-October to give it plenty of moisture through the winter months.
Fertilizing
- Do not fertilize young fruit trees until they have set a crop.
- Once established, fruit production requires regular fertilizing all year long. If there’s good fruit set, fertilize with one pound of calcium nitrate per tree or 1½ pounds of 10-10-10. Cut back the nitrogen in fall and winter to avoid encouraging new growth in those seasons.
How to Prune Plum Trees
When to Prune
- Prune in early spring or mid-summer to avoid infection. The best time for pruning is usually spring for young trees and mid-summer for established ones.
- Do NOT prune in the fall. Winter injury and infection may occur.
Thinning Fruit
“Thinning” is the process of removing developing fruit from a tree in order to increase the overall quality of the produced fruit and to prevent damage to the tree.
- Thinning is usually done about a month after blooming ends in the spring.
- Leave 2–4 inches between each fruit, removing those in between.
- Thinning helps to prevent branches from breaking under the weight of the fruit. If branches do break, prune them back to undamaged wood, ideally cutting back to a natural fork to avoid leaving stubs.
Pruning Japanese Plum Trees
- If you have a Japanese variety, the best pruning method is to create an “open center” shape, where the central trunk is cut short and several large branches radiate outwards from its tip. In the summer of the first year, cut the vigorous shoots that form on the top of the tree by two or three buds. After about a month, check the tree. As soon as you have three wide-angled branches, spaced equally apart, cut back any other branches so that these three are the main branches. In the early summer of the second year, cut back the branches in the middle of the tree to short stubs and prune any shoots developing below the three main branches. After the third year, remove any shoots in the center of the tree to keep its shape.
- Japanese types require heavy pruning to help keep them in shape and to produce better fruit. It is also good to thin out the fruit on these types of trees. You should space the plums about 3 to 4 inches apart on each branch.
Pruning European Plum Trees
- If you have a European variety, the best pruning method is to create a central leader. This shape features a central trunk with branches that spiral out every 5 to 8 inches, making sure that no branch is directly above another. The training for such a system begins in the early summer of the first year, during which time you should remove any shoots that form within 18 inches of the ground. The end result should resemble a Christmas tree.
- European types do not typically require fruit thinning because they do not produce as much fruit as Japanese types. However, the fruit on these types should be spaced about 2 inches apart on each branch.
For more pruning tips, check our spring pruning guide.
Types
There are three major categories of plum trees: European, Japanese, and American hybrids.
European
The hardy European types do well in most regions across the U.S., and are generally self-fertile. If you have space for only one tree, go with a European plum. (However, even self-fertile trees will produce better if cross-pollinated with a second tree.)
For a European type, try the ‘Stanley’. This semi-freestone type works great for the eastern, midwestern, and some of the northwest regions of the U.S. It is self-fertile, meaning no cross-pollination is necessary. It’s harvested in late August, producing medium to large plums with dark blue skin and greenish-yellow flesh and is great for cooking, canning, or eating fresh.
Japanese
The Japanese types flourish where peach trees thrive (warmer regions, generally). The Japanese plums’ early blooms make them more susceptible to spring frosts in colder areas. They need to cross-pollinate with a second variety.
For a Japanese type, try the ‘Satsuma’, which produces large, dark-red plums. This kind is good for eating fresh and canning because of its sweet taste.
American Hybrids
American hybrids are typically the hardiest of the plums, with some varieties surviving as far north as Zone 3. They need to cross-pollinate with a second variety.
American hybrid trees, such as ‘Alderman’, ‘Superior’, and ‘Underwood’, are all popular choices. These trees combine the taste of the Japanese variety with the hardiness of the European variety. These types work well for regional extremes.
Order bare-root, rather than container-grown trees, if possible. Bare-root plants usually establish better. A well-established tree will yield up to 2 bushels of plums from late summer into fall.
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Comments
Hi Melinda,
If the trees are native plums and not grafted, then the suckers (shoots) will grow into identical plum trees and the fruit will be identical to those on the mother tree. If the plum tree was grafted the shoots are coming from the rootstock and will not match the fruit on the mother tree. Best time to dig the suckers is when they are dormant. Dig down far enough to get some roots and then prune the top if it is too tall to keep the roots and top about the same length. You can plant the suckers in big pots or directly in the ground.
Infected twigs should be pruned out and destroyed before buds appear in the spring. It is important to prune at least 2-4 inches below each knot. You can also cut away the diseased tissue down to healthy wood. Burn or bury all the prunings.
Using fungicides will offer significant protection against black knot.
A good guideline is to plant compatible-pollen varieties within 50 feet of one another.
Hello, Ritu: Professor Plum back on the case. Your tree is stressed, and those are sap bubbles that it is exuding. It's possible that you have borers of some type (see if there are little wood specks near the bubble holes), but this is unlikely if the damage is not limited to down near the ground. You also might have a fungal or bacterial infection (well, your tree might have). Or, your tree could just be thirsty and too hot. So... Make sure your tree gets a good watering every 3 days for two weeks. Then every 4 days. Put down some hardwood mulch to help retain the moisture. Get an organic, copper-based fungicide and apply as directed. I am giving you an A+ for caring so much!
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Hi, Martyn: About the only thing we can suggest is to really read carefully and follow the notes about plums (and especially their care and pruning) at the top of this column. One other thing we have found, though, is that people sometimes pick them too soon. You probably have done the following, but if not: Let at least one ripen until it falls off the tree, then test it. This will tell you whether it's a variety/care issue or simply one of timing. Good luck and thanks for asking!