Pruning Plum Trees: When, How, and What to Cut for Better Fruit

Plum trees are forgiving. They’ll produce fruit even if you never prune them. But an unpruned plum becomes a tangled mess of crossing branches, produces smaller fruit, and is far more susceptible to brown rot and bacterial canker. Proper pruning keeps the tree open, productive, and healthy for 20+ years.

The key difference with plums compared to apples and pears is timing. Plums should be pruned in summer, not winter. This single fact prevents most plum tree diseases.

Why summer pruning matters for plums

Most fruit trees get pruned in late winter while dormant. Plums are the exception. The two worst plum diseases, silver leaf (Chondrostereum purpureum) and bacterial canker (Pseudomonas syringae), enter through pruning wounds. Both pathogens are most active in cool, wet weather from November through March.

Summer pruning, done from mid-June through August, allows wounds to heal quickly in warm, dry conditions when disease pressure is lowest. The tree is actively growing and can seal cuts with callus tissue fast.

The rule: Prune plum trees in summer. Only remove dead or broken branches in winter. Everything else waits for summer.

Japanese vs European plums: different growth habits

Understanding which type you have determines how you prune.

Japanese plums (Prunus salicina) include ‘Santa Rosa’, ‘Satsuma’, ‘Methley’, and ‘Shiro’. They grow vigorously, produce fruit on one-year-old wood (last year’s growth) and short spurs. Japanese plums tend toward wide, spreading growth and need more aggressive thinning to prevent overcrowding. Zones 5-9.

European plums (Prunus domestica) include ‘Stanley’, ‘Italian’, ‘Green Gage’, and all prune plums (prunes are just dried European plums). They grow more upright and compact than Japanese varieties. Fruit forms on 2-year-old spurs and older wood. Less vigorous, needing less pruning overall. Zones 4-9.

If you’re not sure which type you have: Japanese plums are generally rounder and juicier with red, purple, or yellow skin. European plums are oval, denser-fleshed, and often blue-purple. Japanese plums ripen earlier (June-July), European plums ripen later (August-September).

The open center (vase) shape

Plum trees perform best when trained to an open center form, also called a vase shape. This means no central leader. Instead, 3-4 main scaffold branches grow outward from the trunk at 45-degree angles, creating a bowl-shaped canopy that lets sunlight reach the interior.

Why open center works for plums:

• Sunlight penetration: Plum fruit needs direct sun to develop sugars and color. An open center lets light into the interior where most fruit hangs.
• Air circulation: Reduces humidity inside the canopy, which discourages brown rot (the #1 plum disease).
• Manageable height: An open center tree stays 12-15 feet tall, making it easy to spray, thin, and harvest without a tall ladder.
• Stronger branch angles: Wide scaffold angles resist splitting under heavy fruit loads.

How to prune a young plum tree (years 1-3)

At planting (year 1)

If you planted a bare-root whip with no branches, cut it back to 24-30 inches above the soil. This forces side branches to develop. Choose 3-4 well-spaced branches growing in different directions as your future scaffold limbs.

If the tree has existing branches, select 3-4 scaffolds that are evenly spaced around the trunk at 18-36 inches above ground. Remove all other branches flush with the trunk. Head back the selected scaffolds by one-third to encourage branching.

Years 2-3

Continue shaping the open center. Remove:

• Any branch growing straight up through the center (these shade the interior)
• Branches growing inward toward the trunk
• Branches that cross or rub other branches
• Suckers from the base and water sprouts from the trunk

Head back scaffold branches by one-quarter to one-third each summer to encourage secondary branching. You’re building the framework that will support decades of fruit production.

How to prune a mature plum tree

Once the tree is 4+ years old and fruiting, annual maintenance pruning keeps it productive and manageable. Do this in July or early August.

Step 1: Remove the obvious problems

Start with dead, diseased, or broken branches. Cut these back to healthy wood or remove them entirely. These cuts can be made any time of year.

Step 2: Open the center

Remove any vigorous upright shoots (water sprouts) growing through the center of the tree. These shade the interior, don’t produce fruit, and waste the tree’s energy. Cut them flush with the branch they’re growing from.

Step 3: Thin for light and air

Stand back and look at the tree from several angles. Anywhere two branches cross, remove the weaker one. Anywhere a section looks dense and crowded, remove 1-2 branches to open it up.

The goal: you should be able to see sky through the canopy from directly below the tree. If you can’t, thin more.

Step 4: Reduce height

If the tree is getting too tall to manage, reduce the height by cutting back tall branches to a lower outward-facing side branch. Don’t just top the tree by cutting branches straight across. Topping causes a flush of water sprouts that make the problem worse.

Step 5: Manage the canopy spread

Japanese plums especially tend to spread too wide. Branches that droop low from fruit weight can be shortened back to an upward-facing side branch. Keep the canopy within a manageable reach for picking and spraying.

Thinning fruit: the overlooked pruning step

Plum trees (especially Japanese varieties) set far more fruit than they can ripen to full size. An unloaded Santa Rosa plum produces medium-sized fruit. A tree with every fruitlet still attached produces small, flavorless plums and breaks branches.

Thin fruit in late May or June, after the natural “June drop” where the tree self-thins some fruitlets. Remove enough so remaining plums are spaced 4-6 inches apart on each branch. Yes, you’re throwing away a lot of tiny plums. The ones that remain will be twice the size and far better quality.

Thinning also prevents biennial bearing, where trees alternate between a heavy crop year and a year with almost no fruit.

Pruning cuts: thinning vs heading

Thinning cuts remove an entire branch back to its point of origin (back to the trunk or to a larger branch). Thinning opens the tree and doesn’t stimulate much new growth. This is your primary pruning cut for mature plum trees.

Heading cuts shorten a branch by cutting it back to a bud or side branch. Heading stimulates new growth below the cut. Use heading cuts on young trees to encourage branching, but use them sparingly on mature trees because they promote the dense, bushy growth you’re trying to avoid.

Most plum pruning on mature trees should be thinning cuts, not heading cuts.

Common plum pruning mistakes

Pruning in winter. The biggest mistake. Winter pruning invites silver leaf and bacterial canker, which can kill entire scaffold branches or the whole tree. Wait for summer.

Removing too much at once. Never remove more than 25-30% of the canopy in a single year. Heavy pruning shocks the tree and triggers a forest of water sprouts. If your tree is severely overgrown, spread the renovation over 2-3 years.

Leaving stubs. Cut branches flush with the branch collar (the raised ring at the base of the branch). Stubs don’t heal and become entry points for decay.

Ignoring the interior. It’s easy to shape the outside of the tree and forget about the middle. But the interior is where disease starts because trapped humidity breeds brown rot. Open it up every year.

Not sanitizing tools. Brown rot and bacterial canker spread on pruning tools. Dip blades in a 10% bleach solution or 70% isopropyl alcohol between cuts, especially when removing diseased wood. Keep your pruning tools sharp for clean cuts that heal fast.

Brown rot prevention through pruning

Brown rot (Monilinia fructicola) is the most common plum disease and it thrives in humid, stagnant air inside dense canopies. Proper pruning is your first line of defense.

Remove any mummified fruit (shriveled, dried fruit left on the tree from last season). These harbor brown rot spores that will reinfect this year’s crop. Pick them off the tree and rake up fallen mummies from the ground.

Prune for airflow. A well-thinned canopy dries quickly after rain, giving brown rot spores less time to germinate. Combine good pruning with a copper or sulfur fungicide spray at bloom time in wet climates.

Tools you’ll need

• Bypass hand pruners: For branches up to 3/4 inch. Bypass cuts are cleaner than anvil cuts.
• Loppers: For branches 3/4 to 1.5 inches. Get bypass loppers with at least 24-inch handles.
• Pruning saw: For branches over 1.5 inches. A folding saw is easy to store and handle.
• Rubbing alcohol or bleach solution: For sanitizing between cuts.

A decent set of all three tools costs $50-100 and will last years with basic maintenance. For guidance on choosing and maintaining pruning equipment, see our fruit tree pruning guide.

Plum tree pruning calendar

Month	What to do
January-March	Remove only dead, broken, or crossing branches. NO live wood cuts.
April-May	Leave the tree alone. It’s flowering and setting fruit.
Late May-June	Thin fruit to 4-6 inch spacing after June drop.
July-August	Main pruning window. Shape, thin, and reduce height.
September	Stop pruning. Let cuts heal before cold weather.
October-December	Remove mummified fruit. No other pruning.

When to renovate an old, neglected plum tree

If you inherited a plum tree that hasn’t been pruned in years, don’t try to fix it all at once. Spread the renovation over three summers:

Year 1: Remove all dead, diseased, and broken wood. Remove obvious water sprouts and any branches growing straight down. That’s it.

Year 2: Open the center by removing 2-3 of the most problematic interior branches. Reduce height by 15-20% by cutting back to outward-facing side branches.

Year 3: Fine-tune the shape. Thin remaining crowded areas. Establish the final open-center form.

By year 4, you should have a productive, manageable tree again. Plum trees respond well to renovation pruning because they grow vigorously and produce fruit on both old and new wood. For more on managing your fruit trees, check mklibrary.com’s seasonal yard guide.