Oleaceae
Olea
Eleven species, of which one matters. The olive is unusual on this site for needing something a warm room cannot supply: a cold winter. Not as a tolerance but as a requirement — flowering is initiated by accumulated chilling, and warmth does not merely fail to provide it, it cancels chilling already banked.
Native to The Mediterranean basin (the cultivated olive)
How Olea generally wants to be treated
Species pages start from this and record only where they differ.
- Light
- Full sun, as much as there is. This is the one plant here with no shade tolerance worth discussing.
- Water
- Water well, then let it dry appreciably before the next one. In a pot the risk is the opposite of drought — an olive sitting in wet compost through a cold winter is the common way to lose one.
- Humidity
- No requirement. It tolerates dry indoor air, and no source publishes a figure.
- Temperature
- Warm summers and a genuinely cold winter. The winter number is the important one and it is in the dormancy field. For cold damage: one study measured complete shoot damage in 'Empeltre' at about 15 °F (-9.5 °C), and UF/IFAS advises protecting below 20 °F (-6.7 °C). Hardiness varies by cultivar more than most people expect.
- Substrate
- Sharp-draining and gritty, on the lean side. A loam-based compost cut with grit suits a container better than anything peat-based.
- Fertilizer
- Modest, through the growing season only. It is adapted to poor Mediterranean soils.
- Propagation
- Semi-ripe cuttings in summer. Seed is slow and does not come true.
- Dormancy
- A real cold requirement, and the numbers are worth knowing because they explain why an indoor olive never fruits. Chill accumulates roughly between 41 and 60 °F (5-15.5 °C) and needs about thirteen to fifteen weeks. Above 61 °F (15.9 °C) chill already banked is cancelled, with the cancellation strongest at 69 °F (20.7 °C) and above. So a plant in a house at 68-72 °F (20-22 °C) is not slowly accumulating what it needs — it is running the counter backwards. Give it an unheated porch, a cold greenhouse or a sheltered spot outdoors at roughly 34-50 °F (1-10 °C) for about three months, above freezing.
- Common problems
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- It never flowers. Nine times in ten this is the chilling requirement, not the light, the feed or the pot
- Root rot in a pot left wet through winter — sharp drainage and a dry-ish cold rest
- Leaf drop after a move between very different temperatures
- Scale and olive knot; the latter gets in through frost cracks, so a plant shuttled in and out is more exposed than one left in a stable cold place
- Olives off your own tree are inedible raw — the bitterness is oleuropein, and it has to be cured out with lye or fermentation
- Nothing documented as toxic to pets, and the ASPCA has no record for it
In the collection
- Olive tree Olea europaea subsp. europaea