Wine · Terminology
Fruit set
When fertilised flowers turn into hard green berries — the moment the crop size is fixed.
Fruit set is the stage immediately after flowering, when fertilised flowers develop into small, hard, green berries. Not every flower makes it: a set rate of 30% is normal, and even in a good year most of the inflorescence falls away.
This is the point at which the size of the crop is effectively decided. Everything after it — canopy work, véraison, the ripening run — changes the quality of the fruit, not how much of it there is.
In practice
- Set rate is driven by flowering-time weather, vine health and the vine's carbohydrate reserves from last season.
- Poor set gives coulure; uneven set gives millerandage.
- Growers do their first serious yield estimate here, and may green harvest (drop bunches) later to concentrate what remains.
- Berries at this stage are hard, green and intensely acidic — sugar has not started to accumulate.
Where you'll meet it
- Vintage reports: "a difficult flowering and poor set reduced volumes by 30%".
- Yield regulations, where appellation rules cap hectolitres per hectare — see AOC.
- The growing cycle guide.
From set to harvest
After set, the berries grow in two phases with a plateau between them:
- First growth phase — rapid cell division and expansion; berries stay green, hard and acidic, accumulating tartaric and malic acid.
- Lag phase — growth slows almost to a stop.
- Second growth phase — begins at véraison: sugars accumulate, acids fall, colour and flavour compounds develop, berries soften and swell again.
Managing what's set
- Green harvesting (vendange verte) removes bunches after set so the vine puts its resources into fewer, better berries — effective but expensive, and arguably a sign the vineyard was over-cropped to begin with.
- Crop thinning at véraison is the alternative timing, when you can drop the laggards that are colouring late.
- Both are trade-offs between volume and concentration, and both are regulated in appellations with yield maxima.