General
Plums are hardy, productive stone fruit trees suited to much of Sweden. European plum (Prunus domestica) dominates in home gardens with cultivars like 'Opal' and 'Victoria'; Japanese plum (P. salicina) needs warmer sites and reliable pollinators. Choose a sunny, sheltered position with good air movement to reduce spring frost damage and disease. Rootstocks determine tree size and hardiness: vigorous seedling or St. Julien A for larger, hardy trees; Pixy for smaller, earlier-bearing trees on sheltered sites. Most cultivars thrive in zones 1–4; the hardiest selections manage zone 5, and a few local varieties may stretch to mild parts of zone 6 in protected sites. Expect bloom in spring and harvest from August to late September depending on cultivar and site.
Light
Full sun (at least 6–8 hours of direct light daily).
Soil type
Deep, well-drained loam enriched with organic matter; avoid waterlogging and high water tables.
Water requirement
Moderate. Keep evenly moist during establishment and fruit swell; deep water in dry spells.
Nutrient requirement
Moderate. Annual compost plus light, balanced organic feed in spring; avoid heavy nitrogen once fruit set.
Precultivation
Plums are almost always planted as grafted trees, not from seed. If raising seedlings for rootstocks or breeding, sow cleaned stones outdoors in autumn (natural cold stratification) or stratify indoors 3–4 months at 1–5°C before spring sowing. Seedlings vary and will not come true to type.
Planting
Plant dormant, bare-root trees in early spring when soil is workable and air temperatures consistently above about 8°C; container trees can be planted from spring to early autumn if watered well. Dig a wide hole, loosen sides, and mix in mature compost but avoid strong fertilizers in the hole. Set the graft union 10–15 cm above soil level. Water in thoroughly and mulch (wood chips, leaves, or compost) keeping mulch a few cm away from the trunk. Stake young trees in windy sites for the first 2–3 years. Maintain a weed-free circle (60–100 cm radius).
Pruning
Prune mainly during the JAS period (July–September) to reduce silver leaf and canker risk. In the first 3 years, form an open-centered or modified central-leader canopy with 3–5 well-spaced scaffold branches. In summer, remove crossing, shaded, dead, or diseased wood; thin crowded fruiting spurs to improve light and fruit size. Limit large cuts; if needed, do them in mid–late summer and make clean cuts just outside the branch collar. Light green pruning in June can redirect vigor. Avoid heavy winter pruning of plums.
Maintenance
Irrigate deeply but infrequently; aim for 20–30 L per week in dry spells for young trees. Renew 5–8 cm of organic mulch annually. Feed in early spring with compost plus a light organic NPK (e.g., 3-3-3) or pelletized manure; a small top-up after fruit set can help on poor soils. Thin heavy crops in early summer to 1 fruit per 8–10 cm on shoots to prevent branch breakage and improve size. Keep trunk guards to deter rodents. Encourage pollinators with diverse flowering understory. Practice good hygiene: remove mummified fruit and fallen leaves to limit disease.
Harvest
Harvest timing varies by cultivar. European plums are usually ready August–September when fully colored and slightly soft with a sweet aroma; fruit should detach with a gentle lift-and-twist. Japanese plums often color earlier but need to soften slightly for best flavor. Handle gently to avoid bruising. Use promptly fresh, for jam, drying, or freezing. Refrigerate ripe fruit for up to a week.
Common issues
• Spring frost on blossom: Site selection and good air drainage help; consider fleece on small trees during cold snaps. Flowering partners increase set. • Silver leaf (Chondrostereum): Prune in dry weather during JAS only; remove infected wood well below symptoms. • Canker and gummosis: Avoid wounds, improve drainage, prune out affected twigs in summer. • Brown rot (Monilinia): Remove mummies, thin fruit for airflow, avoid overhead irrigation near harvest. • Aphids and leaf curl plum aphid: Encourage beneficials, wash off with water, use soft soap if needed. • Plum sawfly/maggots: Collect and destroy infested fruitlets; consider pheromone traps or bagging selected clusters. • Branch breakage from over-cropping: Summer thinning and support props. • Replant disorder in Rosaceae: Avoid planting a new plum where an old Prunus recently stood unless soil is replaced or rested with biofumigant cover crops.
Pollination
Many European plums (Prunus domestica) are partially self-fertile but crop better with a compatible pollinator; most Japanese plums (Prunus salicina) require cross-pollination. Use cultivars flowering in the same period.
Companion plants
Clover or diverse flowering lawn understorey for pollinators, chives/garlic (may deter some borers), comfrey as a dynamic accumulator mulch, borage, phacelia, calendula, white clover, spring bulbs, shallow-rooted herbs.
Incompatible plants
Large shallow-rooted trees (birch, spruce) that compete for water; black walnut (juglone sensitivity); avoid planting stone fruits where old Prunus trees were recently removed without soil remediation (replant disease risk).
