How to Prune a Shikuwasa Tree: Opening a Naturally Dense Canopy

Prune at the end of winter, before the buds move

The window opens once the risk of hard cold has passed and closes as the buds swell for the spring flush. Cutting then lets you read the framework without leaves in the way, gives every wound the whole season to close, and puts the tree's energy into the shoots you chose to keep instead of the ones you are about to remove.

Never prune in autumn. A cut at that point stimulates a soft flush that cannot harden before cold arrives, and on a subtropical citrus with as little frost tolerance as this one that soft growth is the first thing lost. For a container tree that overwinters under cover, the same principle applies with a twist of timing: prune shortly before it goes back outside in spring, not before it comes in.

There is one further reason to hold off, particular to this crop. If you leave part of the crop on the tree to color and sweeten, the tree is still carrying fruit well into the cold months, and you cannot prune sensibly around a hanging crop. Clear the last of the fruit first, then prune.

Density is the problem to solve

Left alone, shikuwasa builds a small dense dome of fine twiggy growth. It looks handsome and it is a liability. Fruit forms all through that congestion, including deep inside where you cannot get a hand in to pick, and the interior stays permanently shaded, still and humid. That is the exact condition scale insects and sooty mold need, and it is also where you will find rubbed and marked fruit at harvest.

So the aim is not a smaller tree. The tree is already small and will stay small. The aim is a tree of the same size that you can see through and reach into. Judge your pruning by whether you can put a hand into the middle of the canopy without a fight and whether patches of daylight come through it when you look up from underneath.

This also affects fruit quality directly. Fruit ripening in dead shade in the middle of a dense tree has less aromatic oil in the rind and less character in the juice than fruit on the sunlit outer wood. Opening the interior is not tidiness; it is how you improve what comes off the tree.

Thorns sit at the leaf bases, most heavily on young vigorous wood and much less on mature branches. They are short but stiff and sharp, and they sit exactly where your hand goes when you reach in to pick. Wear leather gloves that cover the wrist, and rake prunings up with a fork rather than gathering them by hand.

The order of cuts

Work through the tree in a fixed sequence every year. Doing so means each cut is still one you would want to make after the following one, and you never find that you have removed a branch you needed to keep.

1. Suckers from below the graft, first and always Anything growing from below the swollen union is rootstock and it will outgrow the top. The leaf shape below the union differs from the leaf above, which is your reliable test. Cut suckers flush the moment you see them, in any season, not only in the pruning window.
2. Dead, broken and cold-damaged wood Cut back into live green tissue. After a cold winter, wait until the spring flush is genuinely under way before deciding what is dead, because shoots that look brown and finished in late winter often break bud after all.
3. Crossing and rubbing branches Remove the weaker of any two branches that touch. On a tree this twiggy there will be more of these than you expect, and each one is a wound that lets disease in and a place where fruit gets marked.
4. Open the center until you see sky Thin the interior, taking whole small branches out at their point of origin, until patches of daylight come through the canopy. This is the main cut of the year on this tree and the one most people do too timidly.
5. Take out the thinnest twiggy clutter Remove weak pencil-thin shoots that will never carry a decent fruit. They consume light and air and they are what makes the canopy impenetrable in the first place.
6. Shorten anything above comfortable reach Cut leaders that have gone above head height back to an outward-facing side branch. Fruit that needs a ladder on a thorny tree gets picked late or not at all, and picking on time is the whole point with this crop.

Do not clip the outline

The most damaging thing done to this tree is shearing every branch tip to make a neat ball. Shikuwasa flowers on short shoots around the outside of the canopy, so trimming the surface removes most of the following season's flowers in a single afternoon. The tree answers with a mass of vertical thorny regrowth that congests the outside as badly as the inside was congested, and you lose two seasons putting it right.

Thin instead of trimming. Take whole branches out where they join their parent, and leave the branches you keep at full length. The result is an open, lighter tree of the same outline that has kept its fruiting wood, and it does not respond by throwing water shoots.

Keep the annual total modest. A quarter of the canopy is plenty on a plant that is naturally compact and not fast growing. If a tree has genuinely outgrown its container or its corner, reduce it across three seasons rather than in one, and accept that the year after a heavy cut will be a light crop.

Note what you cut and what followed

Write down the date, roughly what proportion of the canopy came off, and where you shortened any height to. This tree grows slowly enough and densely enough that by next winter you will genuinely not remember whether you already reduced a particular branch or only intended to.

Then set the following season's harvest beside that note. A hard cut is one of the reliable triggers for a light year, and having the two entries together turns a vague impression into something you can act on when you decide how much to take off the next time. Add a line on whether the interior stayed open through the summer or closed up again, because a tree that congests itself by midsummer needs a harder interior thin next winter rather than more summer fiddling.