Olive trees in winter: cold limits and protection

What sub-zero temperatures can olive trees tolerate?

It depends on the organ affected and how quickly cold arrives. France Olive describes olive as the temperate-zone fruit tree most sensitive to frost, and gives three median lethal temperatures (LT50)Median lethal temperature (LT50): the cold that kills half the exposed organs. It is a statistical reference, not a sharp boundary. established by Larcher: −12 °C (10 °F) for leaves and buds, −16 °C (3 °F) for main limbs and trunk, −6 °C (21 °F) for roots¹.

Cold that builds gradually from fall is tolerated well: the tree enters dormancy progressively. Beyond −15 to −16 °C (5 to 3 °F), a mature olive's above-ground parts may die, as in 1956; a young plant dies at −6 to −8 °C (21 to 18 °F)¹. Around −6 °C (21 °F), water also begins freezing in bark, potentially splitting it¹.

The RHS rates olive H4, corresponding to minima of −10 to −5 °C (14 to 23 °F), provided it is sheltered². Two circumstances worsen cold damage:

• duration: very low temperatures briefly do less damage than slightly milder temperatures lasting longer, and slow thawing causes less damage than rapid thawing¹;
• waterlogged soil: water conducts cold, and frost may then kill the entire root crown¹.

Can olive trees stay outdoors in winter?

Yes in the ground, wherever winters remain moderate. The real danger is not steady cold but a sudden cold snap after mild weather: mild winters that wake the tree too early are the most worrying¹. On 31 January 1956, Perpignan recorded +12 °C (54 °F) and the following day −8 °C (18 °F); Montpellier subsequently fell to −17 °C (1 °F)¹.

France Olive distinguishes two frost types:

• black frostAdvective frost: a cold, dry air mass arrives from the north-east, often with wind. This is winter frost without ground hoar frost., arriving with a cold air mass, often windy, responsible for major winter freezes; only coastal areas beside a large body of water partly escape;
• white frost, overnight under clear, still skies, more frequent in spring¹.

In cool climates, the RHS recommends planting in the ground only in a very sheltered garden: plant in spring, in well-drained soil near a sunny wall, and stake until established³.

Potted olives in winter: frost-free shelter or fleece

In pots, roots freeze first. No mass of soil insulates them, and they fail around −6 °C (21 °F) while the crown still tolerates around −12 °C (10 °F)¹. The RHS gives two options: bring the pot into frost-free shelter or wrap branches in horticultural fleece³.

Indoors, olive needs a frost-freeA room remaining above 0 °C (32 °F) all winter without necessarily being heated: conservatory, unheated greenhouse or well-lit garage., bright, cool shelter, never a heated living room. It needs around two months at 4 to 10 °C (39 to 50 °F) to flower⁴: a warm winter means no olives the following year.

Outdoors, four steps protect the rootball:

• group pots against a house wall, sheltering roots from cold⁵;
• cover branches with thick fleece, gaining around 2 °C (3.6 °F)³;
• shelter the pot from prolonged rain, beneath an overhang or against a wall, until potting mix drains⁵;
• keep it on pot feet so excess water escapes, and remove the saucer³⁵.

Watering becomes rare but does not stop: an evergreen may be thirsty, especially under cover where rain cannot reach it. Check once a week, and never water when frost is forecast⁵. No fertilizer either: winter feeding is unnecessary in pots⁵, and fall nitrogen makes olive more frost-sensitive⁶.

Pot, terre et arrosage d'été se décident dès la plantation : growing an olive tree in a pot prépare aussi son hiver.

Should you cover an olive tree in winter?

Thick horticultural fleece is sufficient, and only during severe cold. Heavy grades gain around 2 °C (3.6 °F)³: useful for a potted or young tree, but insufficient against prolonged black frost.

For in-ground trees, France Olive reviews orchard protection. Frost candles warm the air down to around −4 to −5 °C (25 to 23 °F), but are expensive and reserved for small areas. Overhead sprinkling, common in fruit growing, is discouraged for olive: ice weight breaks main limbs, and wet foliage encourages peacock spot¹.

In the ground: position does half the work

A well-positioned olive is much less vulnerable to frost. France Olive lists these indirect protections, considered at planting¹:

• avoid hollows and valley bottoms, where heavier cold air collects and stagnates, and poorly drained soil; on slopes, lower trees freeze more than higher ones;
• beware of dense hedges downhill: blocking cold-air drainage increases risk;
• choose a late, local variety suited to the growing area;
• mow grass beneath the tree during risk periods: dense grass cover increases cooling;
• do not prune too early in frost-prone areas: pruned trees restart sooner, exposing young growth¹.

Le calendrier des coupes tient compte de ce risque : pruning an olive tree attend la fin des gelées en zone froide.

Spring frost: the trap of mild winters

Spring frost never kills an olive tree, but it can destroy the crop. Young shoots and flower buds, with sap rising strongly, are the organs affected¹. In France Olive’s French seasonal setting, white frosts occur mainly from March to May.

Two French episodes described by France Olive show the scale. Overnight on 25 to 26 March 2020, humid white frost fell to −7 °C (19 °F) in some municipalities. On 8 April 2021, dry black frost after days of mistral dropped temperatures 5 to 6 °C (9 to 11 °F) in an hour, to −9 °C (16 °F)¹.

Damage is not always immediately visible: some appears only three to four weeks after frost, and apparently normal flowers may be malformed, revealed only by poor fruit set¹.

Frost-damaged olive: what to do afterwards

Scratch the bark before cutting anything: green beneath means wait for regrowth; brown means the branch is dead there¹. Do not cut off supplies: France Olive asks growers to maintain water, nitrogen and trace elements, and protect foliage, since frost wounds admit olive knot bacteria¹.

Recovery pruning, branch by branch according to damage, is detailed in pruning an olive after frost.

Des galles sur les rameaux gelés l'année d'avant : olive diseases commencent souvent par une plaie de gel.

When should you return an olive outdoors in spring?

Only once all frost risk has passed. The RHS returns potted olives outdoors after the last frost³. In France, the popular marker remains the Ice Saints, from 11 to 13 May⁷.

Add your olive tree: Floralens reminds you when to bring it in and take it out, season by season (Pro mode). Get reminders

Frequently asked questions

How do you care for an olive tree in winter?

In the ground, almost nothing: well-drained soil and no fall nitrogen⁶. In pots, bring it into bright, cool, frost-free shelter, or group pots against a wall beneath thick fleece; check watering weekly, never before frost³⁵.

What sub-zero temperature can an olive tolerate?

A mature tree loses leaves and buds around −12 °C (10 °F) and main limbs around −16 °C (3 °F); roots die around −6 °C (21 °F). A young plant cannot tolerate −6 to −8 °C (21 to 18 °F)¹.

Can an olive tree stay outdoors in winter?

In the ground, yes where winters are moderate; a sudden cold snap after mild weather is worst¹. In pots, only against a wall, fleeced and sheltered from rain, because the rootball freezes around −6 °C (21 °F)⁵¹.

Should you cover an olive in winter?

In severe cold, thick horticultural fleece gains around 2 °C (3.6 °F)³. It protects a pot or young tree, not an olive exposed to prolonged black frost.

Should you water an olive in winter?

Little, but not never: check weekly, especially under cover, and do not water when frost is forecast⁵.