Cherry Harvest and Summer Pruning

When you walk through the still-cool garden on an early July morning, just as calendar week 27 gets going, the late sweet cherries hang dark red and plump among the foliage. This is the moment a cherry tree works toward all year: the ‘Kordia’ is at its peak now, the ‘Regina’ follows in CW 28 and 29, and the first sour cherries come in from CW 27 on. It's the loveliest and, at the same time, the shortest harvest of the gardening year.

And it comes with a second benefit that often gets overlooked: the moment right after the last picking is the best time to prune your cherry tree. Harvest and pruning belong together. The ladder is already up, the tree is in full leaf, and you can see at a glance where it has grown too dense. In this article we'll go through both in order: first how to harvest well, then how to prune well.

How to tell a cherry is really ripe

Cherries have one quirk that decides everything else: they don't ripen any further once picked. Unlike an apple, a cherry picked too early will never turn sweet in the basket. It stays sour and bland. So it pays to wait for full ripeness.

Four signs will guide you:

• Colour: the full colour for the variety, dark red to almost black on dark types, yellow-red on pale heart cherries. Light red or greenish means: keep waiting.
• Firmness: plump and round, giving slightly when you press but not mushy.
• Stem release: ripe fruit comes away from the branch easily, stem and all.
• The taste test is the most reliable of the lot.

A side note for anyone who spots “cherry weeks” on old variety labels: that count goes back to the pomologist Christian Truchseß von Wetzhausen and refers to ripening groups, not calendar weeks. One cherry week lasts about 15 days. So the ‘Kordia’ from the 6th cherry week doesn't ripen in CW 6, but right now.

How to harvest gently

Harvest on a dry day, ideally once the morning dew has dried off. Wet cherries bruise easily, split more readily and rot faster.

If you want to keep sweet cherries for a few days, pick them with the stem on, lifting and twisting gently. With the stem they last longer and lose less juice at the stem cavity. Whatever goes straight into a cake or your mouth can happily come off without the stem.

One thing matters: don't tug on the short fruiting spur, the perennial bouquet wood. That's where next year's flower buds sit. Always release the fruit, never the wood.

With sour cherries, it's better to snip the stem with scissors than to tear it off. Every little tear on the branch is an entry point for Monilia fungal spores.

Fresh cherries, by the way, only keep two to three days in the fridge: unwashed, spread loosely on kitchen paper, washed only just before you eat them. To store them longer, freeze them (they keep nine to twelve months) or preserve them.

Birds and split fruit

Two things can ruin your harvest in a matter of days. The first is starlings and blackbirds. A bird net is the only really reliable protection. Mind the mesh size: around 12 to 20 mm, and closer to 12 to 15 mm against clever starlings. Fine enough that no fruit gets pecked through the mesh, but not much over 30 mm, or birds get tangled in it. Only put the net on after flowering, just before the fruit starts to change colour; any earlier and you'll only disturb pollination by insects.

The second is splitting after rain. Fully ripe cherries are high in sugar; if rain suddenly falls after a dry spell, the fruit draws in water, the sugar binds it osmotically, and the internal pressure rises until the skin splits along the seam.

Why you prune the cherry tree now, not in winter

Stone fruit is pruned in summer, right after the harvest, not in the cold and wet of winter. The reason is tree health, and it has three names:

• Monilia (Monilinia laxa), blossom wilt, overwinters on infected wood and mummified fruit. A cut made in warm, dry weather lets the wound seal over quickly, before the spores turn active in spring.
• Silver leaf (Chondrostereum purpureum) is a wound parasite that mainly gets in through pruning cuts in the damp of autumn and winter. In the warm, dry height of summer the infection pressure is low.
• Gummosis, the amber-coloured resin that oozes out, is a stress response that winter pruning encourages. Summer pruning, by contrast, promotes fast wound healing and slows growth at the same time.

There's a practical reason on top of that: winter pruning drives the already vigorous sweet cherries into a thicket of steep water shoots. A little and often in summer beats rarely and brutally in winter.

The pruning guide, step by step

1. Wait for a dry, ideally overcast day right after the last picking. Take sharp bypass pruners and disinfect the blade (around 70% alcohol), especially before you move on to another tree.
2. First take out the obvious problem wood: steep, vertical water shoots, inward-growing shoots and any that cross and rub.
3. Thin the crown out lightly until light and air can pass through. An airy crown dries off quickly after rain, your best protection against fungi.
4. Remove thinner branches right at the branch collar, without leaving a long stub. For thick cherry branches, the most important rule applies: sweet cherries are poor at healing over large flat cuts into old wood, and such wounds stay open for years. So take strong branches out while they're still thin, if you can, to keep the wound small. If a thick branch really has to go, don't lop it off in the middle; instead lead it back to a well-placed, living side shoot (a drop-crotch cut to a pulling or sap branch). That way the branch stays fed, the cut stays small, and you avoid a dead stub that dies back and becomes an entry point for Monilia and silver leaf.
5. Remove all mummified fruit and cut diseased wood well back into healthy wood (rule of thumb: 15 to 20 cm below the visible damage). These prunings do not belong on the compost.
6. Leave the wounds open. Wound sealants are mostly no longer recommended these days, because moisture can get trapped underneath and rot. At most, smooth off large wound edges with a knife.

Sweet and sour cherries are pruned differently

It's worth knowing the difference here, because the two cherries bear on different wood.

The sweet cherry fruits mainly on perennial bouquet wood and is naturally very vigorous. So above all it needs one thing: gentle thinning to keep it airy and within reach. Go easy here. If you're planting new, a weak-growing rootstock like ‘Gisela 5’ keeps the tree small and pickable from the start.

The sour cherry, above all the ‘Schattenmorelle’, fruits almost only on one-year-old long shoots. The shoot that has borne fruit goes bare after the harvest and hangs there empty. So every year it needs a firmer rejuvenation cut: lead old, spent whip shoots back to young side shoots. As a rule of thumb, leave only about three young shoots of 20 to 30 cm per roughly 10 cm of scaffold branch. With the ‘Schattenmorelle’ you can even combine harvest and pruning and cut off whole fruit-laden branches. That saves work and encourages new fruiting wood.

Not all sour cherries need this much pruning: Duke cherries like ‘Köröser Weichsel’ also bear on two- to three-year-old wood and only get thinned every two to three years, much like the sweet cherry.

The typical July worries

The black cherry aphid is more harmless. On older trees a strong jet of water and a bit of patience with ladybirds and lacewings is usually enough. The trees generally grow out of the infestation.

One tree, many years

A cherry tree is not a sprint. It will stand in your garden longer than most of the furniture in your home, and it forgives you your first, second and third year. Whatever you get “wrong” with the pruners this July is a new shoot next year. Start small, take out the obvious, and look in CW 27 next year at what it has made of it. And when you're done: have a coffee under your tree. That's it for this year.