Gadenin日本語Get the appPrune for weight, not for shape
Most citrus pruning advice is about light and airflow. Those matter for a pomelo too, but they come second to a blunter question: can this branch hold two to four pounds (1-2 kg) of fruit at its far end, in wind, in rain, for the eight months or more that the crop hangs there? A limb that would be perfectly adequate on a mandarin will bend to the ground under a pomelo crop and either snap or stay bent for good.
That means favoring wide-angled branches over narrow ones every time. A branch leaving the trunk at a wide angle, somewhere near forty-five degrees or flatter, has a thick strong collar of wood at the join. A branch leaving at a narrow angle traps bark in the crotch as both parts thicken, and that included bark is a fault line. Narrow crotches are where pomelos split, and they split when loaded, which is to say in the year the crop was finally worth having.
So when you have a choice between two competing branches, keep the wide one even if the narrow one is longer or better placed. Take the narrow one out while it is still small enough to cut with pruners. This is the single most valuable thing you can do in the first five years of a pomelo's life and it is almost invisible as work.
| What you are looking at | Keep or cut | Reason |
|---|---|---|
| Branch at a wide angle to the trunk | Keep | Strong collar of wood; carries weight |
| Narrow V crotch with bark pinched in | Cut while small | Included bark splits under a loaded branch |
| Two branches at the same height, opposite | Keep one | Competing leaders weaken each other |
| Long thin branch reaching outward | Shorten by a third | Will bend permanently under one fruit |
| Growth below the graft union | Cut flush, immediately | Rootstock suckers overtake the fruiting top |
| Dead, broken or rubbing wood | Cut any time of year | No season rules apply to damaged wood |
| Branch that will not clear a mower or path | Cut now | You will have to reach under it with a prop later |
When to cut
The main pruning window is after the harvest and before the spring flush begins, in the settled part of late winter or early spring once the risk of hard frost has passed. Cutting in this window means you are working on a bare-ish frame you can actually see, and the tree pushes its response into the new growing season rather than into soft growth that a frost will take.
Never prune a pomelo hard going into cold weather. Fresh cuts and the soft flush that follows them are exactly what cold damages first, and this is the least cold hardy citrus you are likely to grow. If you find yourself wanting to prune in autumn, wait; the only exception is wood that is dead, diseased or broken, which comes out whenever you find it, in any season.
Light summer work is fine and often useful: rubbing out water shoots while they are soft, shortening a branch that is heading somewhere you do not want, taking out a shoot crowding the center. Keep it to a few minutes at a time. Big summer cuts expose interior bark that has never seen direct sun to full midday sun, and citrus bark sunburns readily.
Cut just outside the branch collar, the slight swelling where a branch meets the wood it grows from. Leaving a stub invites dieback and flush-cutting into the trunk removes the tissue that seals the wound. On a cut larger than about an inch (2.5 cm) across on an exposed limb, a coat of white water-based paint on the surrounding bark prevents sunburn better than any wound dressing.
Building the tree in the first five years
The frame you build early is the frame that holds the crop for the next thirty years, so this is worth doing deliberately rather than by instinct. The goal is three to five main limbs, well spaced around the trunk and separated vertically by six inches (15 cm) or more, each leaving at a wide angle, with an open center so light reaches the inner wood and you can get a ladder or an arm in.
Keep the head low. A pomelo canopy that starts at head height puts a four pound (2 kg) fruit somewhere you cannot reach without a ladder, and you will be visiting each fruit more than once: to thin, to prop, and to cut it off with two hands. Low wide branches are also easier to support, which matters more on this tree than on any other citrus.
Do not be tempted to shorten everything back to a neat outline. Heading cuts across the ends of many branches produce a dense shell of twiggy regrowth, a shaded interior and a tree that fruits only on its outside. Thin instead: remove whole branches back to their origin, and leave the ones you keep at full length.
- First dormant season: choose the leader Pick a single strong central stem and remove anything competing with it directly. Leave all the low side growth alone for now; it is feeding the trunk and thickening it, which is exactly what a pomelo trunk needs.
- Second season: select the main limbs Choose three to five side branches spaced around the trunk and separated vertically by six inches (15 cm) or more, all at wide angles. Remove their direct competitors. Aim for the lowest at about two to three feet (60-90 cm) from the ground.
- Third season: open the center Remove branches growing inward across the middle of the tree and any that rub. You are aiming for a bowl shape you can see through, not a solid dome. Keep taking off anything below the graft union on sight.
- Fourth season: shorten the reachers Any branch that has run out long and thin gets shortened by about a third, cutting back to an outward-facing side branch. Judge each one by asking whether it could hold a four pound (2 kg) fruit at its tip without bending to the ground.
- Fifth season onward: maintain and let it crop From here the annual job is small: dead and broken wood out, inward growth out, suckers out, and one or two whole branches removed to keep light in the center. Resist the urge to do more; a settled pomelo needs very little.
Pruning and propping are the same job
A pomelo branch under a full load will bend a long way, and a branch that has bent under load once tends to stay lower afterwards. Every summer, walk the tree while the fruit is swelling and look along each loaded branch from the side. If the tip has dropped noticeably, either put a prop under it or take fruit off it; those are the only two answers and doing neither is how branches break.
A prop is simple: a sturdy timber or steel post with a padded Y at the top, set on a paving slab or a flat stone so it does not sink into wet ground, positioned about two-thirds of the way out along the branch. Pad the crotch of the Y with cloth or hose so it does not chafe the bark, and check after storms that it has not shifted or slipped sideways.
The alternative to propping is thinning, and on a young tree it is the better answer. Take the fruit off rather than support a branch that is not ready to carry a crop. A three-year-old pomelo should be carrying two or three fruit, not eight, whatever it set.
Keep a note each year of which branches needed propping and which broke. After two or three seasons the pattern is usually plain, and it almost always points back to a narrow crotch or an over-long thin branch that could have been dealt with in a dormant season years earlier.