When to Pick Plums: Ripeness, Thinning and Branches That Break

Thin the crop, or the tree breaks itself

Plums set far more fruit than their wood can carry. A branch loaded end to end with touching fruit is carrying several times the weight it was built for, and the failure is not gradual. The limb splits, usually right at the crotch where it joins the trunk, often on a still day with no wind at all. That tear is a large ragged wound in the middle of summer, and it takes years to grow over, if it ever does.

The fix is thinning, done once the natural fruit drop has finished, when the fruit is roughly the size of a hazelnut. Reduce the crop to one fruit every 3 inches (8 cm) along the branch, and about 4 inches (10 cm) for the larger types. Take out anything damaged, marked or misshapen first, then thin the rest by spacing. Where two or three fruit sit in a cluster, leave the best one.

It looks brutal and gardeners consistently under-thin because of it. The total weight you pick barely changes, because the remaining fruit grows substantially larger and sweeter with less competition. What does change is that the branches survive, the fruit dries faster after rain so brown rot spreads less, and the tree has the reserves to flower properly next spring instead of taking a year off.

Where a branch is still bending under weight after thinning, prop it. A forked stick under the limb, or a rope tied to a higher branch, takes the load through the swelling period. Put props in before the fruit colors, not after the branch has already started to split.

Thinning is also the moment to look along each branch for splits already starting at a crotch. A crack found in early summer can be relieved by removing the fruit from that limb. Found in late summer, it is usually too late.

Plums ripen on the tree, and they do it unevenly

A plum picked hard will soften off the tree but it will not get any sweeter. The sugar comes from the tree, and once the fruit is detached that stops. This is why supermarket plums are so often disappointing and why a garden plum picked properly is a different fruit altogether. There is no point picking early to avoid losses; you are trading the whole reason for growing it.

Color alone is unreliable. Plums color up well before they are ripe, and depending on type the ripe color may be deep purple, red, yellow or green. Judge instead by feel and by release. A ripe plum gives slightly under gentle thumb pressure near the stalk end, and separates from the spur when you lift and twist it a little. If you have to pull, it is not ready. Come back in two days.

The other reliable sign is the first fruit falling of its own accord. Once sound, undamaged plums start dropping, the tree is at the start of its picking window, and you have roughly a week to ten days. Ripeness runs through a tree from the outside and top inwards, so plan on going over the tree three or four times rather than stripping it in one session.

Rain near ripeness splits the fruit. The skin has stopped expanding, the flesh takes up water fast through the roots, and the fruit bursts. Split fruit rots within a day or two and then infects sound neighbors. If heavy rain is forecast and the fruit is close, pick everything that gives at all rather than waiting for perfection.

Picking, and what to do with the ones you cannot eat

Plums bruise from the pressure of your own fingers. Handle them by the stalk where you can, lay them in a single layer rather than filling a deep bucket, and keep the bloom, the dusty gray film on the skin, intact. That bloom is the fruit's own protective layer and fruit that keeps it lasts noticeably longer.

1. Go over the tree every two or three days Take only the fruit that releases with a gentle lift and twist. Working outside in and top down follows the way ripeness spreads through the tree.
2. Pick with the stalk attached A plum pulled off leaving its stalk on the tree has an open wound in the skin and rots quickly. If the stalk stays behind, use that fruit first.
3. Sort as you pick, into three lots Sound fruit for eating, marked or split fruit for immediate cooking, and rotting fruit for removal from the garden. Never put the third group back under the tree.
4. Keep the good fruit cool, not cold Ripe plums hold about five days at room temperature and up to two weeks in a fridge, in a single layer. Very cold storage makes the flesh mealy, so use the fridge for a few days rather than weeks.
5. Deal with the glut immediately A thinned tree still gives more fruit than a household eats in a week. Plums freeze well halved and stoned, and cook down for storage. Doing this as you pick is far easier than facing a full crate three days later.

The harvest records that pay off next year

Note the date you started picking and the date you finished, and how many separate passes it took. Over a few years this gives you your tree's actual picking window, which is far more useful than any general advice, and lets you plan around it.

Record the total weight if you can, and separately, roughly how much fruit you lost and to what: split, brown rot, sawfly, birds, or a branch coming down. That breakdown is what tells you which job to do better next season. A year lost mostly to splitting points at watering consistency and picking earlier in wet weather; a year lost to rot points at thinning harder and clearing fallen fruit faster.

Also write down whether you thought you thinned enough. Almost every gardener's honest answer in the first few years is no, and having last year's note in front of you in early summer is the most effective way to make yourself take off the fruit that needs to come off.

If a branch broke, mark where on the tree it was. Plums often fail repeatedly at the same narrow crotch angles, and knowing which limbs are structurally weak tells you where to thin hardest before it happens again.