Tree · Rutaceae
Yuzu
Citrus junos
Behind its long, sharp thorns and knobbly yellow fruit, yuzu is the toughest of the true citrus.
Full sun
Every 7–14 days
USDA 8–11
6–18 ft · 1.8–5.5 m
Overview
Yuzu wears its character on the surface. The fruit is knobbly and uneven, its thick rind dimpled and puckered, ripening from green to yellow. Pressed or scratched, that peel gives up its aromatic citrus oils, and the juice within runs sharp and tart. The tree behind the fruit is a thorny evergreen, keeping its leaves through every season.
The branches are the tree's most striking feature, armed with long, sharp thorns that stand out along the wood. Growth is unhurried at a moderate pace, a grafted tree bearing fruit within a year or two and a seedling taking several. For all its slow build, the wood is tough, holding firm through cold that reaches toward 14°F (-10°C), well past the point most citrus would give in.
Whether rooted in open ground in zone 8 and warmer or held in a wide pot, yuzu keeps the same look: an evergreen frame of thorned branches carrying that dimpled fruit. It stands in full sun, in soil that drains freely, and it needs shelter from the sharpest cold. Handle the thorns with care at pruning, and each autumn the branches hang with fragrant, yellow fruit.
Care
The short version: yuzu wants full sun, slightly acidic well-drained soil, and water once the top of the soil dries. Feed it monthly through the growing season, shelter young trees from hard frost, and mind the long, sharp thorns with thick gloves.
Light
Yuzu ripens its best fruit in full sun, six or more hours a day. In partial shade the branches stretch and space out, growing leggier, and the crop comes lighter.
Water
Let the top inch or so (3 cm) of soil dry to the touch, then water deeply, roughly every 7 to 14 days. A potted tree dries out faster through its walls and wants water more often, while winter calls for a lighter hand.
Soil
Yuzu roots run best in well-drained, slightly acidic sandy loam, loose and gritty and rich with organic matter. A pH of 6.0 to 7.0 keeps iron and the other micronutrients within reach of the roots.
Temperature
The tree holds through a wide sweep of temperatures, about 14°F to 95°F (-10°C to 35°C), the hardest cold any true citrus will take. Young wood is more tender, though, and needs frost cover until the tree matures and firms up.
Humidity
Ordinary humidity of 40% to 60% keeps the foliage in good condition, so outdoors asks for nothing extra. Indoors, where winter air turns dry, a little moisture around the leaves is welcome.
Feeding
Feed monthly through spring and summer with a citrus fertilizer higher in nitrogen and carrying iron, zinc, and manganese to keep the leaves green and the growth strong. Stop feeding late in the season, since a late nitrogen push throws out soft, tender shoots that frost burns.
Pruning
Prune in late winter to early spring to open the shape and cut away dead, crossing, or frost-damaged wood. Watch the branches closely, since they bristle with long, sharp thorns that catch skin and clothing, and wear thick gloves.
Repotting
Shift a potted yuzu into a larger container every 2 to 3 years, before the roots wind around the inside or push out through the drainage holes. Water sliding straight through without soaking in is another sign the roots have filled the pot.
Size & spacing
Yuzu builds to roughly 6 to 18 feet (1.8 to 5.5 m) tall and spreads its thorned branches 5 to 13 feet (1.5 to 4 m) wide, so it needs open ground around it. The final size follows the rootstock and whether the tree runs free in the soil or stays checked in a pot.
When to plant
Yuzu changes through the year in plain sight. Spring brings its flowers, and by late autumn the fruit has swelled and shifted from green to a ripe yellow, thick-skinned and fragrant. Planting waits until the last frost passes in zone 8 and warmer, and new trees are almost always grafted.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Seed late winter to early spring; yuzu is usually propagated by grafting rather than seed
- Plant: After the last frost in spring in zone 8 and warmer
- Harvest: Flowers in spring; aromatic fruit harvested in late autumn as it turns yellow
Hardiness
USDA hardiness zones: 8–11
Temperature: down to -12°C
Troubleshooting
Yuzu wears its troubles on its surface, mostly from cold or from soil that does not suit citrus. The earliest marks appear on the twig tips and the newest leaves, where a change in color or texture gives the cause away. Match what you see below and act before it spreads.
Brown, dead twig tips and fallen leaves after winter
This is cold or frost damage, marked most on young trees pushed past their limit. Scratch the surface of a suspect twig: a dry, brown tip above green, moist wood lower down shows how far the cold reached. Wait for the fresh spring growth, cut back to the living wood beneath, and drape young trees in frost cloth through the hardest freezes.
Fix:
- Wait until new growth resumes in spring, then prune back to live wood
- Protect with frost cloth or move containers under cover during hard freezes
Newest leaves yellowing between still-green veins
The tell here is interveinal chlorosis, a shortage of iron, zinc, or manganese that follows alkaline or waterlogged soil. The youngest leaves pale to yellow while a fine green network of veins stays behind, and the older leaves keep their color. Feed a citrus fertilizer with chelated micronutrients and open up the drainage so the roots can pull in iron again.
Fix:
- Apply a citrus fertilizer containing chelated micronutrients
- Correct drainage and avoid overwatering
Toxicity
The fragrant fruit is safe for people to eat, but the same oils that scent it make the plant a problem for animals. The peel, leaves, and stems are laced with essential oils and psoralens that upset cats, dogs, horses, and others. Keep the oily clippings and fallen peel out of reach of pets and livestock.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Mild
The essential oils and psoralens soaked through the peel, leaves, and stems can set a cat drooling and vomiting or turn it off its food, often with loose stools. Where the oily peel touches, the skin can redden and itch.
Dogs Mild
A dog that gnaws the leaves or peel usually ends up with a churning stomach, bringing vomiting, diarrhea, and a flat, sluggish mood. The same oils can leave a red patch on the skin where they touch.
Horses Mild
The peel, leaves, and stems carry the same sharp citrus oils, so a horse that mouths them may drool and slide into diarrhea or a general gut upset. The strong, pungent scent keeps most horses from taking much.
Rabbits Caution
The oily peel and foliage sit badly in a rabbit's delicate gut, bringing on soft, loose stools or a fading appetite. Keep the trimmings out of the hutch instead of dropping them in as a treat.
Livestock Caution
Goats, sheep, and cattle may lip at fallen leaves or prunings, and a big oily mouthful can loosen the stomach. The sharp bitter taste usually stops them well short of a real dose.
Birds Caution
The essential oils in the peel and leaves can unsettle a bird's digestion, so keep pet birds clear of the clippings. A small taste of the flesh matters far less than the oil-heavy peel.
People Fruit safe
The fruit, its juice, and its zest are prized in the kitchen and safe to eat, which is the whole reason for the tree. Working with a lot of the oily peel in sun can leave sensitive skin reddened, so rinse your hands after juicing.
The branches also bear long, sharp thorns that can scratch curious pets and people.
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
Only a few named yuzu reach beyond Japan, and they differ most in their fruit, from kitchen types to outsized ornamental ones. These two are worth a closer look.
Yuzu Ichandrin
A widely grown seedling-type yuzu, singled out for its extra cold hardiness and its steady set of fruit in cooler climates.
Shishi Yuzu
A tree grown for show more than juice, hung with unusually large, deeply bumpy fruit.
How to propagate
Yuzu is nearly always grafted, which brings quicker fruit and hardier wood, though a seed will grow into a tree given a long enough wait.
GraftingModerate
Late spring through summer when bark slips easily · 1 to 2 years before reliable fruiting
Grafting is the usual commercial method, worked from late spring through summer while the bark peels back cleanly. Set onto trifoliate rootstock, the young tree takes on cold hardiness and vigor and carries its first reliable fruit within 1 to 2 years.
SeedEasy
Late winter to early spring, sown fresh · Several years to fruit
Fresh seed sown in late winter or early spring sprouts readily, but the seedlings inch upward. They take several years to reach fruiting, which makes seed the simplest start rather than the quickest way to a crop.
Myths
Toxic to pets means yuzu fruit must be poisonous to people.
Those are two different things. The animal risk comes from essential oils and psoralens that upset cats and dogs, not from the tart flesh people eat. Yuzu zest, peel, and juice are safe, everyday ingredients, scenting dishes from ponzu sauce to marmalade.
Yuzu is fully winter-proof and shrugs off any freeze.
Yuzu is one of the most cold-hardy true citrus, its wood holding to about 10°F to 15°F (-12°C to -9°C) once established. The young growth is softer, still needing frost protection and still prone to browned, dead twig tips after a hard freeze.