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Aesculus hippocastanum, horse chestnut


Aesculus hippocastanum, horse chestnut

Bud starting to burst

The seeds, when used to play conkers are thought to do much more harm than they actually do.

Blog Entries

Read more about Aesculus hippocastanum, horse chestnut, in these blog entries (most recent first);
'Poisonous Plants 1-2-1' video published
Spring arrives on the River Tweed
Plants and trees in a public park

'Poisonous Plants 1-2-1' video

This short video summarising the story of horse chestnut is just one of a series.



Meaning of the Name

Aesculus hippocastanum, horse chestnut

Aesculus hippocastanum, horse chestnut

In John Gerard's time, this tree was known as Castanea equina. 'Castanea' after the town of Castania in Thessaly where they grew in abundance, and 'equina' for 'horse'. In time, Castanea came to mean 'chestnut' so, when the tree was classified by Linnaeus, to separate it from the edible chestnut which is still in the genus Castanea, he kept the reference to 'horse chestnut' in the species name hippocastanum but changed the genus to Aesculus even though the Latin meaning of 'aesculus' is more to do with oak or birch.

Common Names and Synonyms

Horse chestnut, conker

How Poisonous, How Harmful?

The plant is believed to contain high levels of saponins, called Aesculin, with the highest concentration being in the foliage.

Saponins are poorly absorbed in the gut and seem to be destroyed by heating. Anyone mistaking a horse chestnut for a chestnut is unlikely to come to harm as the action of roasting should destroy the toxins.


In the 1968 book 'Plant Toxicity and Dermatitis', Lampe and Fagerstrom refer to the case of a 4-year old boy who died after a second session of eating raw horse chestnuts.

There are references to occasional occurrences of poisoning in livestock following ingestion of the leaves but these seem to be infrequent.

Folklore and Facts

Aesculus hippocastanum, horse chestnut

Aesculus hippocastanum, horse chestnut

The large seeds of the tree are known as conkers and are used in the game of that name. It has been suggested that the widespread introduction of the tree to Britain in the mid-19th century resulted in the use of the seeds in place of seashells which had previously been the items employed.

Increasingly risk averse attitudes have resulted in some schools banning the playing of conkers or insisting that participants wear safety goggles. Following a media outcry that this was the work of killjoys at the UK's Health & Safety Executive, the HSE issued an official denial of involvement and even sponsored a conker competition. As the text accompanying this poster says, children hitting each other with conkers is a discipline issue not anything to do with 'Elf 'n' Safety'.

In recent years, Horse Chestnut Bleeding Canker, a disease believed to have been brought to this country as a result of unauthorised imports of the tree, has caused substantial harm to the horse chestnut population. In many cases, local authorities have been forced to remove diseased trees both to try and prevent further spread of the disease and to avoid the danger of the sick tree collapsing.

This, often, leads to the allegation that 'spoilsports' are seeking to end the playing of conkers by removing the trees from which they are obtained.

A recent paper reported here by the BBC,  suggests that the leaf miner moth, generally regarded as causing only cosmetic damage, may be capable of reducing fruit weight and seed production and can actually result in the death of the tree.


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Introduction to the A to Z section
Abrus precatorius, rosary pea
Aconitum lycoctonum, wolfsbane
Aconitum napellus, monkshood
Actaea racemosa, black cohosh
Actaea spicata, baneberry
Aesculus hippocastanum, horse chestnut
Amanita muscaria, fly agaric
Aquilegia atrata, columbine
Aristolochia clematitis, birthwort
Artemisia absinthium, wormwood
Arum italicum, Italian cuckoopint
Arum maculatum, cuckoopint
Aspergillus fumigatus
Atropa belladonna, deadly nightshade
Brugmansia suaveolens, angel's trumpet
Bryonia dioica, bryony
Buxus sempervirens, common box
Camellia sinensis, tea
Cannabis sativa, marijuana
Catha edulis, khat
Chelidonium majus, greater celandine
Cimicifuga racemosa, black cohosh
Claviceps purpurea, ergot
Clematis vitalba, old man's beard
Colchicum autumnale, naked ladies
Conium maculatum, poison hemlock
Convallaria majalis, lily of the valley
Cynoglossum officinale, hound’s tongue
Daphne mezereon, spurge olive
Datura stramonium, thorn apple, jimsonweed
Datura suaveolens, angel's trumpet
Delphinium, larkspur
Digitalis spp., foxglove
Dracunculus vulgaris, dragon arum
Echium vulgare, viper’s bugloss
Eranthis hyemalis, winter aconite
Erythroxylum coca, cocaine
Euonymus europaeus, spindle tree
Euphorbia x martinii, red spurge
Euphorbia pulcherrima, poinsettia
Fritillaria spp., fritillary
Galanthus nivalis, snowdrop
Hedera helix, common ivy
Helleborus spp., hellebore
Heracleum mantegazzianum, giant hogweed
Hyacinthoides non-scripta, bluebell
Hyoscyamus niger, black henbane
Ilex aquifolium, holly
Jacobaea vulgaris, ragwort
Juniperus communis, common juniper
Laburnum anagyroides, laburnum
Lactuca serriola, prickly lettuce
Leucojum aestivum, snowflake
Lithospermum officinale, gromwell
Lolium temulentum, darnel
Malus 'John Downie', crab apple
Mandragora officinarum, mandrake
Mercurialis perennis, dog’s mercury
Narcissus, daffodil
Nepeta faassenii, catmint
Nerium oleander, oleander
Nicotiana sylvestris, tobacco
Oenanthe crocata, hemlock water dropwort
Papaver somniferum, opium poppy
Pastinaca sativa, parsnip
Polygonatum odoratum, angular Solomon's seal
Prunus laurocerasus, cherry laurel
Pulsatilla vulgaris, pasque flower
Ranunculus acris, meadow buttercup
Rheum x hybridum, rhubarb
Rhododendron spp.
Rhus radicans, poison ivy
Ricinus communis, castor oil plant
Rosmarinus officinalis, rosemary
Rumex obtusifolius, broad-leaved dock
Ruta graveolens, rue
Salix alba, white willow
Salvia divinorum, sage
Scutellaria laterifolia, Virginian skullcap
Senecio jacobaea, ragwort
Solanum dulcamara, woody nightshade
Solanum melongena, aubergine
Strychnos nux-vomica, poison nut
Symphoricarpos albus, snowberry
Symphytum spp., comfrey
Taxus baccata, yew
Toxicodendron radicans, poison ivy
Thevetia peruviana, yellow oleander
Urtica dioica, stinging nettle
Veratrum album, white hellebore
Verbascum olympicum, Greek mullein
Vinca major, greater periwinkle
Viscum album, mistletoe
Vitex agnus-castus, chaste tree