Californian Olive growers see low crop this year

When growers report a thin olive crop, the cause is often not disaster but biology. Olive trees tend to alternate: a big year followed by a small one. Understanding this rhythm explains a lot about why olive-oil prices and supply lurch the way they do.

Farmers of most crops expect a fairly steady harvest year to year. Olive growers do not. The olive is famously biennial in its bearing: a heavy ‘on’ year, when the tree loads itself with fruit, is typically followed by a light ‘off’ year, when it produces far less. So a report of a poor olive crop is often not a sign of catastrophe but of the tree simply doing what olive trees do.

Why the tree takes a year off

The mechanism is a kind of botanical exhaustion. Ripening a huge crop drains the tree’s resources and, crucially, a heavy fruit load suppresses the growth of the new shoots that would carry next year’s flowers. So a bumper year quietly programmes a lean one to follow, and the tree swings back and forth. It is called alternate bearing, and while good management — pruning, feeding, thinning — can soften the swing, it rarely erases it. The olive likes its rhythm.

When weather piles on

On top of this natural cycle, weather adds noise. A cold snap at flowering, a drought through fruit set, a badly timed heatwave or a late frost can each thin a crop further — and if a rough season lands in an ‘off’ year, the shortfall looks dramatic. That is usually what is happening when you read that a region’s harvest has collapsed: the biennial dip and a bad-weather year have coincided. The next season, more often than not, bounces back.

Why it reaches your kitchen

Because so much of the world’s oil comes from a few big regions that can swing together, alternate bearing shows up on the shelf. A widespread ‘off’ year, or a poor harvest in a giant producer like Spain, tightens global supply and pushes prices up; a strong ‘on’ year eases them. If your favourite oil jumps in price or briefly vanishes, the cause is often not profiteering but a tree, somewhere, taking its scheduled year off. Storable, non-perishable oil buffers some of this — but not all.

The pattern	Heavy ‘on’ year, then light ‘off’ year
Cause	Fruit load suppresses next year’s flowering shoots
Name	Alternate (biennial) bearing
Amplifiers	Drought, frost, heat at flowering or set
Management	Pruning, thinning and feeding soften but rarely erase it
Market effect	Swings in supply and price year to year

The takeaways

• A thin olive crop is often biology, not disaster — the tree’s ‘off’ year.
• Alternate bearing means a heavy year tends to force a light one after it.
• Weather can deepen an off year into an apparent collapse.
• The cycle drives price and supply swings you feel in the shop.

Alternate bearing: common questions

Why do olive harvests vary so much year to year?

Mostly because of alternate bearing: olive trees tend to follow a heavy ‘on’ year with a light ‘off’ year, so crops naturally swing up and down.

What causes alternate bearing?

A heavy fruit load drains the tree and suppresses the new shoots that carry next year’s flowers, so a big year programmes a small one to follow.

Can growers stop it?

Not entirely. Pruning, feeding and thinning fruit can soften the swing, but the biennial rhythm is deeply built into the olive.

Does weather make it worse?

Yes. Drought, frost or heat at flowering and fruit set can thin a crop further, and a rough season in an ‘off’ year can look like a collapse.

Why do olive-oil prices jump around?

Because supply swings with the cycle and with weather in big producing regions; a widespread off year or a poor Spanish harvest tightens the market and lifts prices.

Background on alternate bearing in olives and its effect on harvests and prices.