Tree · Rosaceae
Kwanzan Cherry
Prunus serrulata
Every spring it loads its branches with one unforgettable week of double pink bloom, then leafs out for 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 most flower-heavy of the Japanese flowering cherries, its bare branches vanishing under color in mid-spring. Each blossom is a tight double pompom of 20 to 30 deep-pink petals, ruffled and packed so densely the flower looks almost stuffed, and the tree hangs them in thick clusters that crowd every twig just before or as the leaves push out. It sits in the rose family and was bred purely for that saturated flush of bloom.
The branches lift and arch outward at a moderate pace into a vase-shaped form 25 to 36 feet (8 to 11 m) tall, wider at the crown than the base. When the flowers finish, the leaves take over and the whole canopy burns to a warm orange-bronze in fall. The tree is sterile and essentially fruitless, so no cherries weigh down the twigs, leaving only flower and leaf.
The wood tells a harder story up close. Kwanzan is short-lived, most trees fading within 15 to 25 years as borers tunnel the bark, cankers scar the trunk, and the softening wood cracks in storms. It is a brilliant, brief tree rather than one that thickens into old age.
Care
The short version: full sun, moist but well-drained loam, and steady water while the tree is young. Prune lightly and only just after bloom, keep the bark unscarred, and take it for the short-lived flowering tree it is rather than a lasting shade tree.
Light
In full sun Kwanzan sets the densest, deepest-pink bloom and the strongest orange-bronze in the fall leaves. It will take a little partial shade, but the flowering thins and the 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 its roots are still reaching out into new ground. An established Kwanzan handles moderate drought, but it always looks fuller with steady moisture than through a dry spell.
Soil
Plant in fertile, well-drained loam, whether the grain runs sandy, clay, or silt. A pH of 6.0 to 7.0 suits it, but drainage is the real dealbreaker, since this tree fails on wet or coastal ground.
Temperature
Cold is part of what builds those dense pink pompoms. Kwanzan rides out winters down to -20°F (-29°C) and stands summer heat up to 95°F (35°C), a range that spans zones 5 through 9. A genuine winter chill primes the heavier bloom, and moist roots carry the canopy through hot weather.
Humidity
Ordinary outdoor humidity is fine, so there is no number to manage. Air movement counts for far more here, because still, damp air trapped in the dense 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, sappy new growth draws borers and disease to a tree that is vulnerable enough already.
Pruning
Prune as little as you can, and only to cut out dead, damaged, or crossing branches. Do it just after flowering, make clean cuts flush and stub-free, and never prune in wet weather, because the open Prunus wound is a doorway for cankers and borers.
Repotting
This is a landscape tree, not a container plant, so repotting does not apply once it is in the ground. On a nursery tree, watch for circling roots and water running straight through the pot, and plant it 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), the crown flaring wide like a vase. Give it that full width of open room so the branches can arch out and air can move through the canopy.
When to plant
Kwanzan goes in the ground as a dormant tree, not from seed. A balled-and-burlapped or container tree is planted in early spring or fall, and the deep-pink double flowers break open in mid-spring, before or just as the first leaves unfurl.
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
On Kwanzan, the first signs of trouble surface in the bark and branches, where borers, cankers, and swollen knots show long before the leaves do, and that is part of why these trees are short-lived. Learn to read those early marks on the wood and you can slow the decline. Match what you see below, then act while the tree still has vigor to spare.
Drooping branches above beads of sticky gum and fine sawdust
Fine, pale sawdust piled at the trunk base and beads of clear, sticky sap seeping from the branch crotches are the calling cards of borers chewing tunnels beneath the bark. Cankers often ride alongside them, sinking into wood already stressed or wounded. Cut out and burn the dead or heavily infested limbs. A tree kept firm and full with steady water and mulch, its bark never nicked by a mower or trimmer, shrugs the invaders off best.
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
Leaves gnawed to green lace with pale silk tents in the forks
Leaves eaten down to a fine, lacy net of veins point to Japanese beetles, their shells a hard metallic green shot with bronze. In the branch forks, eastern tent caterpillars pack dense, dirty-white webs of silk that fill with wriggling larvae each spring. Drop the beetles into soapy water, and prune the silken tents out at dawn or dusk while the caterpillars are gathered inside. A settled tree carries light feeding without harm, so a few chewed leaves can stay.
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
Leaf spots whose brittle centers crumble into scattered round holes
Small circular spots dry, crack, and drop their brittle centers, leaving the leaf peppered with clean round holes, the shot-hole look of a fungal or bacterial leaf spot that thrives in damp, crowded air. Rake up and destroy the fallen, spotted leaves so nothing carries over, and thin the canopy with careful pruning to let light and air in. Dry leaves stall the spores, so keep water off the foliage.
Fix:
- Rake and destroy fallen infected leaves
- Improve air circulation through proper spacing and pruning
- Avoid overhead watering that wets foliage
Rough jet-black swellings gripping and lengthening on the twigs
Hard, coal-black lumps swell and lengthen along the twigs, rough as charcoal and wrapped tight around the wood, the unmistakable black knot fungus that girdles branches and warps the tree's clean lines. Cut each knot out several inches below the swelling while the tree is dormant, then burn what you remove. Wipe the pruning blades between cuts, since the spores cling to steel and travel from branch to branch.
Fix:
- Prune out knots several inches below the gall during dormancy
- Destroy pruned material
- Disinfect pruning tools between cuts
Toxicity
For all its color, this tree is genuinely dangerous to animals. The leaves, twigs, bark, and any rare seeds hold cyanogenic glycosides that release cyanide when chewed or, worse, when a cut branch wilts and its leaves soften, and such a limb left in a paddock can kill grazing horses or livestock within minutes. The tree sets little or no fruit, so there is nothing on it for people to eat 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. The gums flush a stark brick red, the pupils blow wide, and panting turns to labored breathing, and any of these calls for an emergency vet trip.
Dogs Toxic
A dog gnawing fallen twigs or wilted leaves faces the same cyanide danger. Ropes of drool, dilated pupils, quick shallow breaths, and a sudden weakness can set in fast, so reach a vet without delay.
Horses Toxic
Horses are the most vulnerable, and the wilted, softening leaves are the real danger. Cyanide can bring on trembling anxiety, a staggering gait, gasping breaths, convulsions, and collapse within minutes, sometimes before anyone sees the branch lying broken in the paddock.
Rabbits Toxic
The same cyanogenic compounds in the foliage make it unsafe for rabbits. Keep them well clear of any trimmings or fallen leaves rather than risk a single bite.
Livestock Toxic
Cattle, sheep, and goats are at serious risk from wilted cherry leaves, which release cyanide and can kill within 15 to 20 minutes of grazing. Fence stock away from the tree, and clear any storm-broken, wilting branches before the animals find them.
Birds Toxic
Cyanide runs through the seeds, leaves, and bark and is dangerous to birds as well, so keep cage birds and poultry from pecking at any plant part.
People Caution
The tree sets little or no fruit, so there is nothing on it to eat. The leaves, twigs, bark, and any rare seeds hold cyanide, so keep children from chewing them and never steep the foliage into a tea.
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 carry their own petal counts, colors, and shapes, some fragrant, some paler, some far longer-lived. These are the ones worth knowing by name.
'Yoshino' (Prunus × yedoensis)
Its fragrant single blossoms open a pale pink that fades toward white, the cherry behind much of the Washington DC display, more spreading and a touch longer-lived than Kwanzan.
'Shirofugen'
Its double flowers open pink-tinged, drain to white, then blush pink again as they age, and it comes into bloom later than most flowering cherries.
'Amanogawa'
A narrow, columnar tree whose semi-double fragrant flowers glow pale pink up a tight, upright frame that slips where a spreading cherry cannot.
Weeping Higan cherry (Prunus subhirtella 'Pendula')
Slender branches cascade in green ropes hung with early single pink flowers, and it outlives Kwanzan by a good margin.
'Mount Fuji' / 'Shirotae'
A wide, flat-topped tree whose fragrant white semi-double flowers ride along low, sweeping limbs.
How to propagate
Kwanzan is not raised from seed. Because the cultivar is sterile, every tree is a clone taken by skilled grafting, joining living wood to living rootstock in a way that sits 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 crowds every flower with petals rather than seed, it will not come true from seed, so growers join scion wood to compatible cherry rootstock by grafting or budding to hold the cultivar exact. Bench grafting is done in late winter to early spring and budding in summer, and the young tree takes 1 to 2 years to grow into saleable size. This is skilled, close hand work, well outside casual propagation.
Stem cuttingsDemanding
Early summer from softwood · Several months to root, then 1-2 years to establish
Soft, green early-summer cuttings can be set under mist with a rooting hormone, though they push roots unevenly and many simply blacken and fail. Even a cutting that strikes needs several months to root and another 1 to 2 years to establish. Grafting stays the reliable route.
Myths
Those pink blossoms turn into edible cherries by summer.
Kwanzan is a double-flowered ornamental, packed with petals rather than built to set fruit. It is essentially sterile and rarely bears anything at all, so the deep-pink spring bloom is the whole reason to grow it, never a harvest.
Everything on a cherry tree except the pit is safe for animals.
The leaves, twigs, and bark hold the same cyanogenic glycosides packed into the seeds. Wilted leaves are the classic cause of fast horse and livestock poisoning, which is why a limb snapped off and drooping after a storm is far more dangerous than any pit.