Gadenin日本語Get the appTreat the thorns as a safety problem, not an inconvenience
Most citrus have thorns you work around. Yuzu has thorns that send people to hospital. They reach three inches (7 cm), they are stiff and sharp enough to puncture deeply, and because they sit at the leaf bases along the whole length of a shoot, a branch you pull out of the canopy drags a row of them across your forearm and your face.
The equipment is not optional. Wear leather gauntlets that cover the forearm, eye protection, and a thick long-sleeved jacket, not a row cover that thorns pass straight through. Use long-handled loppers and a pole pruner so your hands stay outside the canopy. Never prune a yuzu alone at the top of a ladder.
Change the way you remove wood. Instead of cutting a branch at the base and hauling it out, cut it into short lengths from the tip inward, letting each piece fall clear, and take the final cut at the base only when what remains is a bare stub you can hold. Rake the prunings up with a fork rather than gathering them by hand; thorns stay dangerous in the grass for a long time and go through a shoe sole.
Puncture wounds from citrus thorns are deep and dirty and can carry infection or a fragment of thorn into the joint. Wash any puncture thoroughly and get medical advice if it is deep, near a joint, or if it swells over the following days.
Prune at the end of winter, before growth moves
The window opens once the hardest frosts are past and closes when the buds start to swell for the spring flush. Cutting then lets you see the true shape without leaves in the way, gives you the whole season for the wounds to close, and puts the tree's energy into the shoots you chose to leave.
Do not prune in autumn. A cut then stimulates a soft flush that will not harden before cold, and on a plant whose entire value is its cold hardiness that is a real loss. Do not prune in summer either, beyond rubbing out an obvious misplaced shoot with a gloved hand, because you are cutting away wood that is carrying this year's fruit.
Yuzu is slow growing and fruits on the outer parts of the canopy, so it needs far less cutting than a vigorous lemon. Take no more than a fifth of the canopy in a year. Removing a lot at once produces a mass of vertical, viciously thorny regrowth and costs you two seasons of fruit.
The order of cuts
Work through the tree in a fixed order. Doing so means every cut you make is one you would still make after the next one, and you never find you have taken out a branch you needed.
- Suckers from below the graft, first and always Growth from below the swollen union is rootstock. On the hardy rootstocks used for yuzu the giveaway is the leaf: three leaflets on one stalk instead of one, and thorns that are shorter but broader at the base. Rootstock outgrows the top, so remove it flush the moment you see it, at any time of year, not only in the pruning window.
- Dead, broken and frost-damaged wood Cut back into live green tissue. After a hard winter, wait until the spring flush starts before deciding what is dead, because yuzu shoots that look brown and lifeless in late winter frequently break bud.
- Crossing and inward-facing branches Remove the weaker of any two branches that rub. Take out branches heading into the middle of the tree, because a congested interior is where you cannot safely reach and where scale and sooty mold build up.
- Open the center enough to see daylight Thin the interior until you can see patches of sky through the canopy. Air movement is the main defense against scale, and light reaching inner wood is what keeps fruiting close to the trunk rather than only on the outer tips.
- Cap the height last Shorten any leader heading above about eight feet (2.4 m) back to an outward-facing side branch. Fruit you cannot reach on a thorny tree is fruit you will not pick, and a low, wide yuzu is far safer to work on than a tall one.
What not to cut
Do not strip the thorns off in the hope of a manageable tree. Each thorn removed is a wound, and a tree covered in hundreds of small wounds is an invitation to disease. Thorniness declines naturally as wood matures, so an older yuzu is genuinely easier to handle than a young one. The exception is a handful of thorns on branches directly beside a path, which you can snip off individually without harm.
Do not shorten every branch tip to tidy the outline. Yuzu flowers on short shoots on the outside of the canopy, so an all-over trim removes most of next season's flowers. Thin whole branches out at their origin instead of clipping the surface.
Do not paint the cuts. Wound paints trap moisture against the wood. A clean cut just outside the branch collar, made with sharp tools, seals itself.
| Job | When | How much |
|---|---|---|
| Remove rootstock suckers | On sight, any season | All of them, cut flush |
| Remove dead and frost-killed wood | Late winter, after buds move | All of it, back to green |
| Thin crossing and inward branches | Late winter | Enough to see daylight through |
| Reduce height | Late winter | Back to an outward side branch |
| Snip thorns beside a path | Any season | Individually, only where needed |
| Total removed in one year | Late winter | No more than a fifth of the canopy |
Keep a note of what you took
Write down the date you pruned, roughly what proportion of the canopy came off, and where you reduced the height to. Yuzu grows slowly enough that you will not remember from one year to the next whether you cut a branch back once or three times.
Pair that with the crop you get the following season. A heavy cut is one of the reliable triggers for a bare year, so having the pruning note and the harvest weight side by side is what lets you see the connection rather than guessing at it.