Tree · Rosaceae
Plum
Prunus domestica
Rooted in deep, sun-warmed soil and pruned each year, a plum tree bows its branches under glossy, ripe fruit.
Full sun
Every 7–14 days
USDA 4–9
10–20 ft · 3–6 m
Overview
A plum tree carries its fruit in glossy, rounded stones of color, from the deep blue freestone plums of the European types to the reddish-purple, juice-heavy fruit of the Japanese ones. It stands in the rose family beside cherries, peaches, and apricots, a spreading deciduous tree whose branches bend under ripening fruit. Both groups want a sunny spot and deep, well-drained soil, and both hold their crop on a wide, open framework of wood.
The fruit takes its time to arrive on the branch. Some European plums set their blue plums alone, while most Japanese plums need a second compatible tree blooming at the same time before the flowers hold. Once pollination takes, a healthy tree comes into bearing in about 3 to 5 years and then hangs heavy with fruit for decades.
That long life is written into the wood and the fruit alike. Coal-black knots can ring the twigs and brown rot can pucker the ripening plums into shriveled mummies, and a clean, open canopy of light-filled branches is the surest guard against both. Clear the dropped fruit and dead wood, and the tree keeps its skin smooth and its plums firm and full of color.
Care
The short version: full sun, deep and well-drained soil, and steady moisture while the fruit fills out and colors. The open canopy is pruned each winter, feeding is light in early spring, and a pollinizer is matched to any variety that needs one.
Light
Plums want full sun, ideally 6 or more hours a day, to sweeten the fruit and dry the leafy canopy after rain. They will take a little partial sun, but shade thins both the crop and the open, airy branch structure that keeps disease off the wood.
Water
Let the top half of the root zone dry between waterings, then water deeply. Young trees need regular water, while established ones weather some drought yet size and set fruit far better with even moisture as the plums swell and fill out. Soggy ground is the one thing to avoid, since it rots the roots and crown.
Soil
Plant in deep, well-drained loam worked full of dark organic matter. A pH of 6.0 to 7.0 suits the tree, and the single thing to avoid is heavy, waterlogged soil that rots the roots and crown.
Temperature
Plums are cold-hardy, taking a range of roughly -29°F to 95°F (-34°C to 35°C). European types hold their bare branches through hard winters, though a late frost during bloom can still brown the open flowers and cost a season's fruit.
Humidity
Ordinary outdoor humidity in the 40% to 70% range suits the tree, so it is not a number to manage. Airflow matters far more, since long damp spells in a crowded, leafy canopy are what brown rot and black knot wait for.
Feeding
Feed once in early spring before the buds break, using a balanced fertilizer or a simple nitrogen source. A light hand is best, since too much nitrogen forces soft, sappy growth that fruits poorly and catches disease.
Pruning
Prune every year in late winter while the tree stands bare and dormant. Open Japanese types to a vase shape and train European types to a modified central leader, cutting out dead, diseased, and crossing wood, carving out any coal-black knots, and thinning the canopy so light and air reach the fruit.
Repotting
Plums are normally grown in the ground rather than in pots. Dwarf trees in large containers are the exception, needing their soil refreshed or a move to a bigger container every 2 to 3 years.
Size & spacing
A standard plum reaches 10 to 20 feet (3 to 6 m) tall and spreads its branches nearly as wide, so give it room. Space trees far enough apart that the mature canopies do not touch, which keeps air moving through the leaves and disease in check.
When to plant
Plums keep to the seasons in plain view. Bare-root, grafted trees go in as leafless wands in early spring while they are dormant and the soil can be worked, the branches froth with pale bloom in early to mid spring, and the fruit hangs and colors from late summer into early fall as it softens.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Early spring while dormant as bare-root, grafted trees, after the soil can be worked; container trees can go in from spring to early summer.
- Harvest: Blooms early to mid spring; European plums ripen late summer to early fall (about August to September), while Japanese plums often ripen somewhat earlier.
Hardiness
USDA hardiness zones: 4–9
Temperature: down to -34°C
Troubleshooting
Most plum trouble is written on the tree itself, in the black knots on the wood, the browned blossoms, and the softening fruit. Read those marks early and a little pruning or cleanup clears them before they spread. Match what you see below, then act while it still does some good.
Rough coal-black swellings gnarling twigs and limbs
Rough, coal-black swellings that ring a twig and harden into woody knots are black knot, a fungus that slips into new spring shoots and rebuilds those galls year after year. In the first season they show as olive-green, velvety cushions before they crack and blacken. Cut each knot out in late winter, taking the branch a full 6 to 8 inches below the swelling, and burn or bin the prunings. Wipe the saw between cuts, and pull out any wild plums or cherries nearby that keep the fungus supplied.
Fix:
- Prune out knots in late winter, cutting at least 6 to 8 inches below each gall, and destroy the prunings.
- Disinfect pruning tools between cuts and remove any infected wild plums or cherries nearby.
Brown-rotted blossoms and fruit fuzzed with tan spore tufts
Blossoms that brown and collapse on the spur, and fruit that softens under gray-tan tufts of powdery spores, are the marks of brown rot, a fungus that thrives in warm, wet weather at bloom and again as the plums ripen. Soft rot spreads through the flesh until the fruit shrivels into dark, wrinkled mummies that cling to the branch. Pick off and destroy every rotted fruit and mummy. In a wet year, a labeled fungicide at bloom and again as the fruit colors keeps the crop clean.
Fix:
- Remove and destroy rotted fruit and mummies during the season and at cleanup.
- Apply a labeled fungicide at bloom and again as fruit ripens in wet seasons.
Curved crescent scars pocking young fruit before it falls
A thin crescent scar cut into the skin of a young plum is the signature of the plum curculio, a small weevil that tucks its eggs inside the developing fruit. The grubs tunnel through the flesh, the fruit drops early, and a windfall sliced open reveals a curved, C-shaped white larva at its core. Gather and destroy every dropped fruit to break the cycle, and apply a labeled insecticide at petal fall while the adults are active.
Fix:
- Collect and destroy dropped, infested fruit to interrupt the life cycle.
- Apply a labeled insecticide at petal fall and shuck split when adults are active.
Curled, sticky leaves with sooty mold
Leaves that curl, distort, and yellow under a shiny sticky film are the work of aphids, clusters of soft-bodied insects packed onto the tender new growth. Their honeydew coats the foliage and darkens into a black film of sooty mold, and the shine draws lines of ants up the stems. A hard jet of water knocks a light colony loose, and insecticidal soap or horticultural oil clears the rest, leaving the lady beetles and lacewings to finish before anything stronger is used.
Fix:
- Wash light infestations off with a strong jet of water or use insecticidal soap or horticultural oil.
- Preserve natural enemies such as lady beetles and lacewings and treat only when populations are high.
Toxicity
The ripe, juicy flesh is good to eat, but the leaves, stems, bark, and hard pits are not. Those parts hold cyanogenic compounds that release cyanide when chewed or wilted, and limp, wilted prunings are especially dangerous to grazing animals. Keep pets and livestock away from clippings and fallen pits, and never let anyone crack open a stone.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Toxic
A lick of the soft ripe flesh rarely causes a cat more than a mildly upset stomach. The danger sits in the leaves, twigs, and the hard cracked pit, which release cyanide when chewed, so drooling, bright red gums, and labored breathing mark an emergency.
Dogs Toxic
Dogs are drawn to the smooth, hard fallen pit, and that is the real danger, since the kernel inside and the wilting leaves give off cyanide while the whole stone can lodge in the gut. Vomiting, panting, and weakness after chewing the tree call for a fast vet visit.
Horses Toxic
Horses face the sharpest risk, and limp, wilted leaves blown into a paddock are the classic trap. The cyanide they hold can turn the gums brick-red, blow the pupils wide, and bring on staggering and collapse within minutes, so prunings and fallen branches stay well out of reach.
Rabbits Toxic
The leaves, bark, and slim twigs of plum make unsafe browse for a rabbit, as the same cyanogenic compounds gather as the foliage wilts and dries. The prunings are set aside entirely and familiar rabbit-safe greens offered instead.
Livestock Toxic
Cattle, goats, and sheep are most often poisoned by drooping, wilted leaves off a fallen or pruned branch, which concentrate cyanide as they dry and curl. Distress, gasping, and collapse can follow within an hour, so stock is fenced clear of every plum pruning.
Birds Caution
Birds peck the soft ripe flesh with ease, as many wild fruit-eaters do. The hard pit and the leaves are the concern, since the cyanide inside the kernel turns dangerous if a bird cracks it open, so only pitted flesh is offered.
People Ripe fruit safe
The ripe, juicy flesh is wholesome and safe fresh or cooked. The hard stone at the center is the exception, holding cyanide that is released if it is cracked, so it is spat out and children are kept from chewing it.
The hazard is the wilting leaves, twigs, and the pits (cyanide), not the ripe flesh. Keep pets and livestock away from prunings, wilted foliage, and fallen pits; pitted ripe plum flesh is a safe occasional treat in moderation.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Hundreds of plum cultivars exist, differing in the color and size of their fruit, but a few turn up again and again in home orchards. These are the ones worth knowing by name and by look.
Stanley
A widely grown, self-fruitful European prune plum bearing deep blue freestone fruit whose flesh parts cleanly from the pit for drying, cooking, and fresh eating.
Damson
A small European plum with tart, blue-black skin, prized for the jams, preserves, and cooking it makes rather than for fresh eating.
Santa Rosa
A popular Japanese plum whose juicy reddish-purple fruit is partly self-fruitful yet crops most heavily with a compatible pollinizer nearby.
Methley
An early, heat-tolerant Japanese plum, self-fruitful and sweet-fleshed, that suits warmer regions.
How to propagate
Plums are not started from seed the way an annual is. Named trees are budded or grafted onto rootstock, while the cleaned stones are saved mostly for raising those rootstocks or breeding something new.
GraftingModerate
T-budding in late summer when bark slips, or whip grafting onto rootstock in late winter while dormant. · Bears fruit in roughly 3 to 5 years depending on rootstock and cultivar.
Named plums do not come true from a pit, so growers bud or graft them onto plum rootstocks that set the tree's size, vigor, and tolerance of the soil. A single bud is slipped under the loosened bark in late summer when it peels back cleanly, or a dormant scion is whip grafted onto rootstock in late winter. The young tree then knits together and comes into bearing in about 3 to 5 years, depending on the rootstock and cultivar.
SeedModerate
Cold-moist stratify the cleaned pits over winter, then sow in spring. · Several years to fruit, and seedlings are not true to type.
Raising a plum from the cleaned stone suits rootstock work and breeding, not copying a named plum. The pits are scrubbed clean, held through a cold, moist winter to break their dormancy, and sown in spring, though fruit is still several years off and the seedling will not match its parent.
Myths
A plum tree bears nothing unless another tree stands nearby.
It turns on the type of plum. Many European plums such as Stanley are self-fruitful and set fruit alone, while most Japanese plums and a few European ones need a compatible cultivar in bloom at the same time to fruit well. The variety settles the question before a lone tree goes in.
Prunes come off some other fruit with no link to plums.
There is no separate fruit at all, since prunes are simply dried plums. They come from certain freestone European cultivars whose flesh dries down around the pit without spoiling, which is why only some plums shrivel into good prunes.
Plum pits are harmless to chew.
The hard pit, along with the leaves and stems, holds cyanogenic compounds that release cyanide when crushed or chewed. A swallowed whole pit can also block the gut, so the stone is spat out and kept away from pets and children.