Tree · Rosaceae
Kwanzan Cherry
Prunus serrulata
Plant it for one unforgettable week of double pink bloom each spring, and treat it well the rest of the year.
Full sun
Every 5–10 days
USDA 5–9
25–36 ft · 7.6–11 m
Overview
Kwanzan is the showiest of the Japanese flowering cherries, the one that turns a whole street pink for a week in mid-spring. Each blossom is a double pompom of 20 to 30 deep-pink petals, and the tree carries them in dense clusters that open just before or as the leaves unfold. It belongs to the rose family and was bred purely for that flush of flower.
Where it shines, it shines hard. The tree grows at a moderate clip into a vase-shaped form 25 to 36 feet (8 to 11 m) tall, then closes the year with orange-bronze fall color. It is sterile and essentially fruitless, so there's no messy fruit drop and no edible harvest, just the bloom and the foliage.
The catch is that Kwanzan does not live long. Most trees decline within 15 to 25 years, troubled by borers, cankers, and weak wood that storms can break. Plant it knowing it's a brilliant, short chapter rather than a tree your grandchildren will climb.
Care
The short version: full sun, moist but well-drained loam, and steady water while the tree is young. Prune only lightly and only just after bloom, keep the trunk free of injury, and don't expect it to be a long-lived shade tree.
Light
Give Kwanzan full sun for the heaviest bloom and the best fall color. It will take a little partial shade, but flowering thins out and damp, shaded foliage invites the leaf diseases this tree is already prone to.
Water
Keep the soil moist but well-drained, watering every 5 to 10 days while the tree is young and roots are still spreading. An established Kwanzan handles moderate drought, but it always does better with steady moisture than with a dry spell.
Soil
Plant in fertile, well-drained loam, whether sandy, clay, or silt. A pH of 6.0 to 7.0 suits it, but the real dealbreaker is drainage, since this tree fails on wet or coastal ground.
Temperature
Kwanzan is hardy across a wide range, from about -20°F (-29°C) up to 95°F (35°C), which covers zones 5 through 9. It needs a real winter chill to bloom well and tolerates summer heat as long as the roots stay moist.
Humidity
Ordinary outdoor humidity is fine, so there's no number to manage. Air movement counts for far more here, because still, damp air around the canopy is what lets leaf spot and brown rot take hold.
Feeding
Feed lightly in early spring before bloom with a balanced slow-release tree fertilizer. Go easy on the nitrogen, since soft, lush growth draws borers and disease to a tree that's vulnerable enough already.
Pruning
Prune as little as you can, and only to take out dead, damaged, or crossing branches. Do it just after flowering, make clean cuts without stubs, and never prune in wet weather, because Prunus wounds are an open door to cankers and borers.
Repotting
This is a landscape tree, not a container plant, so repotting doesn't apply once it's in the ground. If you're holding a nursery tree, watch for circling roots and water running straight through the pot, and get it planted before it sits rootbound.
Size & spacing
Expect a mature tree 25 to 36 feet (about 8 to 11 m) tall with a spread of 25 to 30 feet (about 8 to 9 m). Give it that full width of open room so the vase-shaped crown can develop and air can move through the canopy.
When to plant
Kwanzan is planted while dormant, not started from seed. Set a balled-and-burlapped or container tree in the ground in early spring or fall, and it rewards you with its double pink bloom in mid-spring, before or just as the leaves break.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Plant balled-and-burlapped or container trees in early spring or fall while dormant.
- Harvest: Showy double deep-pink pompom-like flowers (about 20-30 petals each) in mid-spring, typically before or as leaves emerge; essentially fruitless.
Hardiness
USDA hardiness zones: 5–9
Temperature: down to -29°C
Troubleshooting
Most Kwanzan trouble shows up in the bark and branches before the leaves, which is part of why these trees are short-lived. Learn to read the early signs of borers, disease, and black knot, and you can slow the decline. Match what you see below, then act while the tree still has vigor to spare.
Wilting branches with sawdust frass and oozing sap
This points to borers tunneling under the bark, often working alongside trunk cankers that move into stressed or wounded wood. Cut out and burn the dead or heavily infested limbs. The best defense is a vigorous tree, so water and mulch well and never let a mower or trimmer nick the trunk.
Fix:
- Remove and destroy heavily infested or dead wood
- Keep the tree vigorous with proper water and mulch to resist attack
- Avoid wounding the trunk with mowers or trimmers
Lacy, skeletonized leaves or webbed nests in the branches
Metallic green Japanese beetles strip leaves down to the veins, while eastern tent caterpillars spin silken nests in the branch forks each spring. Knock the beetles into soapy water and prune out the caterpillar tents in the early morning or evening when the larvae are home. An established tree shrugs off light feeding, so there's no need to chase every chewed leaf.
Fix:
- Hand-pick beetles or knock them into soapy water
- Prune out and destroy tent caterpillar nests in early morning or evening
- Tolerate minor feeding on established trees
Spotted leaves with holes punched clean through
Circular spots whose centers fall away leave a shot-hole look, the sign of a fungal or bacterial leaf spot that takes hold in damp, crowded conditions. Rake up and destroy the fallen leaves so the disease can't carry over, and open the canopy with careful pruning. Keep water off the foliage, since wet leaves are what let the spores spread.
Fix:
- Rake and destroy fallen infected leaves
- Improve air circulation through proper spacing and pruning
- Avoid overhead watering that wets foliage
Hard black knots swelling along the twigs
These rough, coal-black swellings are black knot, a fungus that girdles twigs and branches and slowly disfigures the tree. Cut each knot out several inches below the gall while the tree is dormant, then burn what you remove. Wipe your pruning tools between cuts, or you'll carry the spores from branch to branch.
Fix:
- Prune out knots several inches below the gall during dormancy
- Destroy pruned material
- Disinfect pruning tools between cuts
Toxicity
This tree is genuinely dangerous to animals. The leaves, twigs, bark, and any rare seeds hold cyanogenic glycosides that release cyanide when chewed or wilted, and a wind-thrown branch left in a paddock can kill grazing horses or livestock within minutes. The tree sets little or no fruit, so there is nothing for people to eat here either. Keep pets and stock away from prunings and fallen limbs, and clear them promptly.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Toxic
A cat that chews the leaves, twigs, or bark can take in cyanide. Watch for brick-red gums, wide pupils, panting, and labored breathing, and treat any of these as an emergency.
Dogs Toxic
Dogs that gnaw fallen twigs or wilted leaves face the same cyanide risk. Drooling, dilated pupils, fast breathing, and weakness can come on quickly, so get to a vet without delay.
Horses Toxic
Horses are highly vulnerable, and wilted leaves are the real danger. Cyanide can bring on anxiety, staggering, gasping, convulsions, and collapse within minutes, sometimes before anyone notices the tree came down in the paddock.
Rabbits Toxic
The same cyanogenic compounds make the foliage unsafe for rabbits. Keep them away from any trimmings or fallen leaves rather than risk it.
Livestock Toxic
Cattle, sheep, and goats are at serious risk from wilted cherry leaves, which can release cyanide and kill within 15 to 20 minutes of grazing. Fence stock away from the tree and clear any storm-broken branches before animals find them.
Birds Toxic
Cyanide from the seeds, leaves, and bark is dangerous to birds as well, so keep cage birds and poultry from pecking at any plant parts.
People Caution
The tree sets little or no fruit, so there is nothing to eat here. The leaves, twigs, bark, and any rare seeds hold cyanide, so keep children from chewing them and never brew tea from the foliage.
Keep pets and especially horses and livestock away from fallen, pruned, or wilted branches and leaves, which are the most dangerous. Dispose of prunings promptly.
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
Kwanzan is one of many flowering cherries, and the others trade its dense double bloom for different shapes, scents, and longer lives. These are the ones worth knowing by name.
'Yoshino' (Prunus × yedoensis)
This is the fragrant, single pale-pink-to-white cherry behind much of the Washington DC display, more spreading and a touch longer-lived than Kwanzan.
'Shirofugen'
Its double flowers open pink-tinged, fade to white, then blush pink again, and it blooms later than most flowering cherries.
'Amanogawa'
A narrow, columnar tree with semi-double fragrant pale-pink flowers, it slips into tight spaces where a spreading cherry won't fit.
Weeping Higan cherry (Prunus subhirtella 'Pendula')
Graceful weeping branches carry early single pink flowers, and it outlives Kwanzan by a good margin.
'Mount Fuji' / 'Shirotae'
A wide, flat-topped tree with fragrant white semi-double flowers spread along low, sweeping limbs.
How to propagate
Kwanzan is not a plant you raise from seed. Because the cultivar is sterile, every tree is a clone propagated by skilled grafting, which puts it well beyond casual backyard propagation.
GraftingDemanding
Late winter to early spring (bench grafting) or summer (budding) · 1-2 years to a saleable grafted tree
Because Kwanzan is sterile and double-flowered, it won't come true from seed, so growers graft or bud scion wood onto compatible cherry rootstock to keep the cultivar exact. Bench grafting happens in late winter to early spring and budding in summer, and it takes 1 to 2 years to grow on a tree ready to sell. This is skilled work, well outside casual propagation.
Stem cuttingsDemanding
Early summer from softwood · Several months to root, then 1-2 years to establish
You can try softwood cuttings in early summer under mist with a rooting hormone, but they root unevenly and many simply fail. Even a cutting that takes needs several months to root and another 1 to 2 years to establish. Grafting stays the reliable commercial route.
Myths
Flowering cherries like Kwanzan grow edible cherries.
Kwanzan is a double-flowered ornamental bred for show, not for the table. It is essentially sterile and rarely sets fruit at all, so you grow it for the spring bloom, never for a harvest.
Cherry trees only endanger animals through their pits.
The leaves, twigs, and bark carry the same cyanogenic glycosides as the seeds. Wilted leaves are the classic cause of fast livestock and horse poisoning, which is why a branch that snaps off in a storm matters more than any pit.