Plum care guide: when & how to prune, fertilize and spray
Prunus domestica / P. salicina · USDA zones 4–9
Productive and fairly easy. Prune in the growing season to avoid silver leaf disease, and cut out black knot in winter.
☀️ Sun
Full sun.
💧 Water
Moderate.
🪱 Soil
pH 6.0–7.0. Well-drained loam. Compost.
How and when to prune plum
Remove black knot galls
When: 3–8 weeks before the last spring frost.
- zones 3–5: about Mar 15 – Apr 19
- zones 6–7: about Feb 18 – Mar 25
- zones 8–10: about Dec 31 – Feb 4
Galls are easy to spot on bare winter branches, and removing them before spring stops spores spreading.
- Cut each infected twig 4 in (10 cm) below the black swelling.
- Burn, bag or bury the galls. Don't leave them on the ground.
Main prune in early summer
When: 6–10 weeks after the last spring frost.
- zones 3–5: about Jun 21 – Jul 19
- zones 6–7: about May 27 – Jun 24
- zones 8–10: about Apr 8 – May 6
Plums are prone to silver leaf fungus, which infects through winter pruning cuts. Pruning in active growth is much safer.
- Remove crossing, crowded and upward-growing shoots.
- Japanese plums: keep an open vase and cut back vigorous new shoots by a third.
- European plums: keep a central leader and do lighter thinning.
Thin young fruit
When: 5–8 weeks after the last spring frost.
- zones 3–5: about Jun 14 – Jul 5
- zones 6–7: about May 20 – Jun 10
- zones 8–10: about Apr 1–22
Trees set far more fruit than they can size up. Thinning gives bigger, better-tasting fruit, prevents broken branches and stops the tree alternating between heavy and empty years.
- Wait until after the natural 'June drop', when fruit is about marble to walnut size.
- Twist or snip off fruit so the survivors are spaced 3–4 in (8–10 cm) for Japanese types apart along the branch.
- Remove the smallest, damaged or misshapen fruit first.
- It feels wasteful, but you'll harvest about the same weight of much better fruit.
Spraying & disease prevention for plum
Curculio protection
When: 3–5 weeks after the last spring frost, then every 1 weeks (3 times a season).
- zones 3–5: about May 31 – Jun 14
- zones 6–7: about May 6–20
- zones 8–10: about Mar 18 – Apr 1
Plum curculio lays eggs in young fruit right after petal fall.
- Coat young fruit with kaolin clay at petal fall and renew it after rain for 3–4 weeks.
What to use: 🌿 Kaolin clay (e.g. Surround WP)
Common plum problems and how to fix them
Black knot
Signs: Hard, black, tar-like swellings on twigs.
What to do: Cut out 4 in (10 cm) below each knot in winter and destroy. Lime sulfur at bud break.
Plum curculio
Signs: Crescent-shaped scars on young fruit; fruit drops early.
What to do: Kaolin clay from petal fall; collect dropped fruit.
Plum care FAQ
When should I prune plum?
Remove black knot galls: 3–8 weeks before the last spring frost (around Feb 18 – Mar 25 in zones 6–7). Main prune in early summer: 6–10 weeks after the last spring frost (around May 27 – Jun 24 in zones 6–7). Thin young fruit: 5–8 weeks after the last spring frost (around May 20 – Jun 10 in zones 6–7). Productive and fairly easy. Prune in the growing season to avoid silver leaf disease, and cut out black knot in winter.
What should I spray on plum?
Curculio protection (3–5 weeks after the last spring frost). Products: Kaolin clay (e.g. Surround WP). Always follow the label.
What soil does plum need?
Well-drained loam. Preferred pH 6.0–7.0. Compost.
How much sun and water does plum need?
Sun: Full sun. Water: Moderate.
What are common plum problems?
Black knot: Hard, black, tar-like swellings on twigs. Cut out 4 in (10 cm) below each knot in winter and destroy. Lime sulfur at bud break. Plum curculio: Crescent-shaped scars on young fruit; fruit drops early. Kaolin clay from petal fall; collect dropped fruit.
More fruit care guides
Timings are given relative to your average frost dates, with examples for typical US climates. Always read and follow product labels.