Horse chestnut Aesculus hippocastanum
Horse chestnut (Aesculus hippocastanum) is a deciduous perennial tree in the Sapindaceae family, native to Balkans (Albania, Greece, Bulgaria). It grows 15–22 m (49–72 ft) tall and 12–18 m (39–59 ft) wide, wants full sun and moderate water, and is hardy to about -34 °C (-29 °F). Space plants about 12 m (39 ft) apart.
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Horse chestnut at a glance
| Type | Perennial tree, deciduous |
|---|---|
| Family | Sapindaceae |
| Mature height | 15–22 m (49–72 ft) |
| Mature spread | 12–18 m (39–59 ft) |
| Spacing | 12 m (39 ft) centre to centre |
| Sun | Full sun, at least 5 h of direct sun a day |
| Water | Moderate; drought tolerance low, waterlogging tolerance low |
| Soil pH | 5.5–7.5 |
| Cold hardiness | About -34 °C (-29 °F) once established (roughly USDA zone 4) |
| Heat stress | Likely above about 32 °C (90 °F) |
| Flowering | from about May for 2–3 weeks (northern hemisphere; later in cold climates, earlier in warm ones) |
| Wind tolerance | Moderate |
| Pollinator value | High |
| Edible | Not grown as food |
| Native to | Balkans (Albania, Greece, Bulgaria) |
| Common in gardens of | 🇩🇪 Germany, 🇬🇧 United Kingdom, 🇫🇷 France, 🇷🇺 Russia |
Is Horse chestnut toxic?
- People: moderately toxic
- Cats: moderately toxic
- Dogs: moderately toxic
- Parts: conkers (seeds), leaves, bark
Seeds contain saponins (aesculin) that cause vomiting and can be dangerous to children and dogs; conkers are not edible.
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 Horse chestnut
No well-documented helpful pairing. Group it with plants that like full sun and moderate water.
Shared pests and diseases
- Phytophthora ramorum: Sudden oak death pathogen; rhododendron, viburnum, camellia and pieris spread it to oaks and larch. Evidence B
Questions about Horse chestnut
- How far apart should I plant Horse chestnut?
- About 12 m (39 ft) apart, centre to centre. A mature plant spreads 12–18 m (39–59 ft).
- Does Horse chestnut need full sun?
- Full sun: at least 5 hours of direct sun a day.
- How much water does Horse chestnut need?
- Moderate water. Drought tolerance is low and waterlogging tolerance low.
- How cold-hardy is Horse chestnut?
- It tolerates about -34 °C (-29 °F) once established, roughly USDA zone 4.
- When does Horse chestnut flower?
- From about May for 2–3 weeks (northern hemisphere; later in cold climates, earlier in warm ones).
- Is Horse chestnut poisonous to cats and dogs?
- For cats it is moderately toxic; for dogs moderately toxic; for people moderately toxic. Seeds contain saponins (aesculin) that cause vomiting and can be dangerous to children and dogs; conkers are not edible.
- What grows well with Horse chestnut?
- There is no well-documented companion pairing for Horse chestnut. Group it with plants that like the same sun (full sun) and water (moderate).
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
- Leaves often brown by late summer from leaf-miner moth and leaf blotch; also prone to bleeding canker.
- Very large; falling conkers and husks make it a poor tree near paths or seating.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
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