Holm oak Quercus ilex
Holm oak (Quercus ilex) is an evergreen perennial tree in the Fagaceae family, native to Mediterranean basin (evergreen forest and maquis). It grows 15–25 m (49–82 ft) tall and 12–20 m (39–66 ft) wide, wants full sun and low water, and is hardy to about -15 °C (5 °F). Space plants about 12 m (39 ft) apart.
Plan Holm oak in your garden →
Free. Draw your beds, then watch it grow through the year in 2D and 3D.
Holm oak at a glance
| Type | Perennial tree, evergreen |
|---|---|
| Family | Fagaceae |
| Mature height | 15–25 m (49–82 ft) |
| Mature spread | 12–20 m (39–66 ft) |
| Spacing | 12 m (39 ft) centre to centre |
| Sun | Full sun, at least 5 h of direct sun a day |
| Water | Low; drought tolerance high, waterlogging tolerance none |
| Soil pH | 5.5–8.5 |
| Cold hardiness | About -15 °C (5 °F) once established (roughly USDA zone 7) |
| Heat stress | Likely above about 42 °C (108 °F) |
| Flowering | from about May for 3–5 weeks (northern hemisphere; later in cold climates, earlier in warm ones) |
| Wind tolerance | High |
| Pollinator value | Low |
| Edible | Yes: acorns (sweet forms, after leaching) |
| Native to | Mediterranean basin (evergreen forest and maquis) |
| Common in gardens of | 🇬🇧 United Kingdom, 🇫🇷 France, 🇮🇹 Italy, 🇪🇸 Spain, 🇬🇷 Greece |
Is Holm oak toxic?
- People: mildly toxic
- Cats: mildly toxic
- Dogs: moderately toxic
- Parts: acorns, leaves
Oak tannins in acorns and leaves upset the stomach and can damage kidneys in dogs and livestock.
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with Holm oak
No well-documented helpful pairing. Group it with plants that like full sun and low water.
See Holm oak in a botanical garden
It grows in these sample gardens, which you can walk through in 3D:
- UC Botanical Garden, Berkeley (1 plants)
- Kew: glasshouses and rock garden (1 plants)
Questions about Holm oak
- How far apart should I plant Holm oak?
- About 12 m (39 ft) apart, centre to centre. A mature plant spreads 12–20 m (39–66 ft).
- Does Holm oak need full sun?
- Full sun: at least 5 hours of direct sun a day.
- How much water does Holm oak need?
- Low water. Drought tolerance is high and waterlogging tolerance none.
- How cold-hardy is Holm oak?
- It tolerates about -15 °C (5 °F) once established, roughly USDA zone 7.
- When does Holm oak flower?
- From about May for 3–5 weeks (northern hemisphere; later in cold climates, earlier in warm ones).
- Is Holm oak poisonous to cats and dogs?
- For cats it is mildly toxic; for dogs moderately toxic; for people mildly toxic. Oak tannins in acorns and leaves upset the stomach and can damage kidneys in dogs and livestock.
- What grows well with Holm oak?
- There is no well-documented companion pairing for Holm oak. Group it with plants that like the same sun (full sun) and water (low).
Sources and evidence
Evidence grade B (B: extension service or peer-reviewed).
- RHS Plant Finder, Royal Horticultural Society
- Plants of the World Online (taxonomy, native range), Royal Botanic Gardens, Kew
- ASPCA Toxic and Non-Toxic Plant List, ASPCA
Notes and assumptions
- Evergreen oak with leathery, grey-felted leaves; salt-wind tolerant. Kew has had holm oaks since the 18th century.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
Related plants
- Sweet chestnut Castanea sativa
- English oak Quercus robur
- Southern live oak Quercus virginiana
- European beech Fagus sylvatica
- Coast live oak Quercus agrifolia
- Cork oak Quercus suber
- Northern red oak Quercus rubra
- White oak Quercus alba