Study and careerWinemaking & vineyard
Coulure and millerandage: when vine flowers don't become grapes
Two French words every wine student meets: coulure, when flowers fail to set, and millerandage, the 'hens and chicks' bunch. What causes them, and what they do to yield and quality.
Updated October 2026
Rewritten by Alper Billik, Advanced Sommelier
4 min read
The short answer: both are forms of poor fruit set at flowering. Coulure (in English, shatter) is when flowers or tiny berries drop off, leaving straggly bunches with few grapes. Millerandage (hens and chicks, or shot berries) is when the bunch sets but mixes normal berries with small, often seedless ones. Both cut the crop; millerandage can sometimes add concentration.
Where they happen in the vine's year
The vine's year runs from budburst to flowering, fruit set, véraison (when grapes change colour) and harvest. Flowering lasts only a short time in late spring or early summer. Each flower that is pollinated and fertilised can become a berry, but never all of them: University of Maryland Extension puts normal fruit set at 30–50% of the flowers, and calls anything under 30% poor (UMD Extension). Some drop is the vine thinning its own crop. Coulure and millerandage are when it goes too far.
Coulure: flowers that fail
- What you see: loose, straggly bunches with gaps. Flowers and young berries fall soon after flowering.
- Weather: cold (below about 15°C) or very hot weather at flowering hurts pollination. Rain and cloud stop pollination and cut photosynthesis, so the flowers go short of sugar.
- Vine balance: vines that are too vigorous send their energy into shoots instead of flowers; weak vines have too little leaf to feed them. Too much nitrogen fertiliser can push vigour.
- Nutrition and disease: a lack of boron, zinc or nitrogen, and mildew on the young clusters.
- Prone varieties: Grenache, Merlot and Malbec are well known for it.
Millerandage: hens and chicks
- What you see: a bunch of normal berries (the hens) mixed with small, often seedless ones (the chicks).
- Causes: poor weather during flowering and fruit set, boron or zinc deficiency, and some viruses. Fanleaf virus, spread by a soil nematode, is known for poor set and shot berries.
- The upside: small berries have more skin for every drop of juice, so they can bring concentration.
- The downside: a smaller crop and uneven ripeness within the same bunch.
What it means for the wine
| Coulure | Millerandage | |
|---|---|---|
| English name | Shatter | Hens and chicks, shot berries |
| What happens | Flowers or young berries drop | Berries set, but many stay small and seedless |
| Yield | Lower, sometimes sharply | Lower |
| Quality | Looser bunches dry faster after rain, so less rot | Can add concentration, but ripeness is uneven |
| Main causes | Weather at flowering, vine imbalance, nutrition | Weather at flowering, boron or zinc, viruses |
- English name
- CoulureShatter
- MillerandageHens and chicks, shot berries
- What happens
- CoulureFlowers or young berries drop
- MillerandageBerries set, but many stay small and seedless
- Yield
- CoulureLower, sometimes sharply
- MillerandageLower
- Quality
- CoulureLooser bunches dry faster after rain, so less rot
- MillerandageCan add concentration, but ripeness is uneven
- Main causes
- CoulureWeather at flowering, vine imbalance, nutrition
- MillerandageWeather at flowering, boron or zinc, viruses
When you read that a vintage was small, look first at the weather during flowering. It is often where the story starts.
What growers can do
- Choose the site and the variety with flowering weather in mind.
- Keep the vine in balance through pruning, canopy work and moderate fertiliser.
- Check boron and zinc and correct them before flowering.
- Plant clean, virus-tested vines and protect young clusters from mildew.
- Accept the weather. No one can stop a cold, wet week at flowering.
More on what can go wrong in the vineyard: vine diseases, fungal to phytoplasma. What the berry is made of: pulp, skin and seeds. All the vineyard words: French wine terms.
Quick quiz
Question 1
What is coulure?
- a)Grapes splitting after rain
- b)Flowers or young berries failing and dropping
- c)Grapes shrivelling on the vine
- d)Leaves turning red in autumn
Show answerAnswer
b) Flowers or young berries failing and dropping. Coulure, or shatter, is a failure of fruit set: flowers or tiny berries fall, leaving loose bunches.
Question 2
What is the English nickname for millerandage?
- a)Hens and chicks
- b)Noble rot
- c)Green harvest
- d)Bleeding
Show answerAnswer
a) Hens and chicks. Big berries (hens) next to small, often seedless ones (chicks). Also called shot berries.
Question 3
Which nutrient deficiency is linked to poor fruit set?
- a)Calcium
- b)Boron
- c)Iron
- d)Sulfur
Show answerAnswer
b) Boron. Boron, and also zinc, are needed for the pollen tube to grow.
Question 4
Which of these varieties is well known for coulure?
- a)Riesling
- b)Grenache
- c)Sauvignon Blanc
- d)Cabernet Franc
Show answerAnswer
b) Grenache. Grenache, along with Merlot and Malbec, is famously prone to coulure.
Question 5
When do coulure and millerandage start?
- a)At budburst
- b)During flowering and fruit set
- c)At véraison
- d)At harvest
Show answerAnswer
b) During flowering and fruit set. Both are problems of flowering and fruit set, in late spring or early summer.
Questions people ask
What is the difference between coulure and millerandage?
With coulure, flowers or young berries drop, so the bunch has few grapes. With millerandage, the berries stay, but many are small and seedless next to normal ones.
Is millerandage bad for wine?
It lowers the crop and makes ripeness uneven, but the small berries have more skin for their juice, which can add concentration.
Can growers prevent coulure?
Not completely, because the weather at flowering decides a lot. Balanced vines, good nutrition (boron and zinc) and healthy clusters lower the risk.
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