Which fertilizer for olive trees, and when?

When should you fertilize an olive tree?

Feed olive trees in late winter and spring, never in fall. France Olive explains why: fall nitrogen makes olive trees vulnerable to frost¹. The garden calendar has two dates:

• mid-February in France Olive’s French seasonal calendar for organic fertilizer or manure, which needs time to decompose; lightly scratching it into the surface speeds nutrient release¹;
• late March in that French seasonal calendar for complete or organo-mineral olive fertilizer, spread beneath the tree at the packet dose².

Only nitrogen has a prohibited season. Nitrogen-free fertilizer can be applied at any time if the tree lacks a nutrient or has had an exceptionally heavy crop¹. After spring frost, do not cut off supplies: France Olive asks growers to maintain nitrogen and trace elements to support new leaf emergence³.

Une fois la saison des apports passée, reste le froid : overwintering an olive tree se décide selon le pot et la région.

Add your olive tree: Floralens reminds you when to feed, with reminders following the seasons (Pro mode). Get reminders

Which fertilizer should you choose for an olive tree?

A complete fertilizer is the simplest option, containing the three major nutrients: nitrogen, phosphorus and potassium. Garden centers sell mineral or organo-mineralA fertilizer combining organic matter (manure, plant waste) with mineral nutrients: it feeds the tree and enriches soil humus in one application. olive formulas, and France Olive considers these applications sufficient in most cases². The association stresses that a well-pruned but underfed tree grows very slowly and yields little.

Label figures always follow the same order. A 5-10-8-2 fertilizer contains 5% nitrogen, 10% phosphorus, 8% potash and 2% magnesia¹. France Olive's handbook gives 6-3-8 as a suitable olive formula and recommends comparing nitrogen content: a fertilizer well supplied with nitrogen is preferable to one mainly rich in potash⁴.

Nutrient	What it provides
Nitrogen (N)	Tree growth, leaf renewal, flowering quality4
Phosphorus (P)	Roots and main limbs, budbreak, fruit set, fruit firmness4
Potassium (K)	Crop quality, water economy, resistance to disease and frost4
Magnesium (Mg)	Photosynthesis, fertilization, drought resistance4

What dose? For a mature, unirrigated olive, France Olive allows 250 to 300 g (8.8 to 10.6 oz) of nitrogen annually, equivalent to 2.5 to 3 kg (5.5 to 6.6 lb) of complete fertilizer at 10% nitrogen or 5 to 6 kg (11 to 13.2 lb) at 5%. An irrigated tree receives 20 to 50% more⁴. Formula choice then depends on age and situation.

Olive tree	Fertilizer	Why
Mature, in the ground	Complete or organo-mineral olive fertilizer, late March in France Olive’s French calendar	Nitrogen, phosphorus and potassium in one application2
Young, not yet productive	High phosphorus, moderate nitrogen, no potash	Phosphorus supports rooting; potash waits until the first crops2
Potted	Balanced liquid feed monthly, slow-release granules at planting	A pot's potting mix is depleted quickly56
Soil low in organic matter	Manure or compost in late winter	Feeds the tree and replenishes soil reserves1

Harvested olives remove much more nitrogen and potassium than shoot growth does: France Olive therefore bases the dose on the expected crop, reducing it slightly when a small crop is expected².

Manure, compost and coffee grounds: natural fertilizer

Organic fertilizers suit olive trees, releasing nutrients at the rate the tree absorbs them¹. Horse manureAnimal droppings mixed with bedding (straw, sawdust) and decomposed in a heap: low in nutrients but high in organic matter. has an approximate analysis of 0.8-0.3-0.9, sheep manure 0.6-0.4-1.2. These concentrations are low, and only half the manure becomes available within the year: the rest feeds subsequent years, hence the value of a supplement¹.

• Well-rotted, straw-rich manure: avoid fresh manure low in straw or sawdust, whose nitrogen washes away in heavy rain. Sheep manure makes soil more alkaline¹.
• Compost: 30 to 40 kg (66 to 88 lb) per tree every 4 to 5 years, in winter, especially on bare soil⁴.
• Shredded prunings: left beneath the tree, they return some extracted nutrients to the soil and reduce fertilizer needs accordingly².

Coffee grounds are not an olive fertilizer. They mainly supply nitrogen, with variable pH, sometimes acidic, sometimes alkaline; spread alone, they compact into a crust⁷. Put them in compost at no more than 20% by volume. Other garden uses are covered in using coffee grounds.

What should you put around an in-ground olive?

Spread fertilizer beneath the canopy, where roots work, rather than against the trunk. For an unirrigated olive, France Olive spreads it around the tree in a band at least 2 m (6.6 ft) wide beneath the canopy edge, preferably before rain to dissolve it⁴.

• Drip-irrigated olive: place fertilizer near emitters in a 1 m (3.3 ft) band⁴.
• Olive watered in a basinA soil hollow around the base that holds irrigation water above the roots.: apply in the watered area; two applications annually are possible⁴.

Light surface cultivation improves the effect of organic and coated fertilizers⁴; stay away from the trunk and work dry soil several days after rain, since olive knot bacteria also enter through injured roots⁸.

Potted olive: liquid feed every month

In pots, give balanced liquid feed once a month during the growing season. This is the RHS rule for an olive intended to flower and fruit⁵. A pot holds only limited potting mix, and container plants quickly exhaust its reserves⁶.

1. At planting or repotting, mix slow-release granules into potting mix⁵.
2. During growth, add liquid fertilizer to watering water monthly, onto already moist potting mix⁵⁶.
3. From late summer to mid-spring, stop: winter feeding is unnecessary⁶.

Diamètre, terre, arrosage d'été et abri d'hiver : growing an olive tree in a pot demande des gestes que la pleine terre ignore.

How can you boost an olive tree's growth?

A struggling olive first needs regular complete fertilizer, not a miracle product. France Olive places feeding first, before pruning². Three targeted supplements then exist:

• boron before flowering improves flower-cluster formation and fruit setThe transition from a fertilized flower to a young fruit just after flowering.¹;
• zinc after flowering, often lacking in southern French olive soils¹;
• foliar fertilizers, sprayed onto current-year shoots, correct deficiency quickly; however, they are ineffective on an old tree neglected for years¹.

Before buying, a soil analysis, quoted by the French source at around €85 excluding tax for a complete analysis, shows what is actually missing and avoids adding nutrients already in excess². Leaf analysis completes the picture: the French source’s seasonal example samples in late July or during winter dormancy. Follow the tree’s local growth cycle.

Too much nitrogen or poor timing: mistakes

Excess nitrogen does more damage than deficiency. It creates a vigorous but fragile tree, and France Olive links it to several problems¹:

• frost, when fall nitrogen produces tender tissue before winter¹;
• alternate bearing, a heavy year followed by an empty one, worsened by poorly adjusted nitrogen feeding¹;
• olive knot, whose bacterium becomes more virulent with excess nitrogen⁸;
• Verticillium wilt, for which France Olive recommends reducing nitrogen⁹.

Conversely, a genuine shortage of nitrogen, magnesium, zinc, potassium or boron weakens the tree and contributes to decline¹⁰. Follow the packet dose: doubling it does not feed twice as well².

Un feuillage qui pâlit n'a pas toujours faim : yellow olive leaves se lisent selon leur position et la saison.

Galles, branches qui sèchent ou taches cerclées : olive diseases se reconnaissent à d'autres signes que la faim.

Frequently asked questions

When should you fertilize olive trees?

Time feeding to local late winter and spring growth. France Olive’s French calendar gives manure or organic feed in mid-February and complete fertilizer in late March¹². In pots, liquid feed monthly during growth⁵. Never apply nitrogen in fall, as it makes the tree vulnerable to frost.

What should you put around an in-ground olive?

Complete olive fertilizer in late March in France Olive’s French seasonal example², spread in a band at least 2 m (6.6 ft) wide beneath the canopy edge, away from the trunk; then every 4 to 5 years, 30 to 40 kg (66 to 88 lb) of compost or straw-rich manure in winter⁴.

Are coffee grounds good for olive trees?

Not as fertilizer: they mainly supply nitrogen, their pH varies and they form a crust when spread alone⁷. Put them in compost, below 20% by volume.

How can you boost an olive tree’s growth?

Start with complete fertilizer each spring: an underfed tree grows very slowly². Boron before flowering helps flowers set fruit; zinc afterwards addresses a common deficiency in southern France¹.

Which fertilizer for a potted olive?

Balanced liquid feed monthly during the growing season, with slow-release granules mixed into potting mix at planting⁵. Nothing from late summer to mid-spring⁶.