Autumn is here again and conkers will soon be falling from the trees to the delight of children up and down the country. We all know conkers are good for playground battles, but how much do you know about these iconic signs of autumn? Discover more with our conker facts.

What is a conker?

Conkers are the glossy brown seeds of the horse chestnut tree. They grow in green spiky cases and fall to the ground in autumn - the shells often split on impact to reveal the shiny conker inside.

Can you eat conkers?

No. Conkers contain a poisonous chemical called aesculin. Eating a conker is unlikely to be fatal, but it may make you ill. They are poisonous to most animals too, including dogs, but some species such as deer and wild boar can eat them. Curiously, conkers are also poisonous to horses despite the tree being named after them.

Sweet chestnuts and conkers - what's the difference?

Sweet chestnut and horse chestnut trees are not actually related, but their seeds are similar. Both come in green shells, but horse chestnut cases have short, stumpy spikes all over. Inside, the conkers are round and glossy.

Sweet chestnut cases have lots of fine spikes, giving them the appearance of small green hedgehogs. Each case contains two or three nuts and, unlike conkers, sweet chestnuts are edible. Roasted chestnuts are a popular Christmas dish, while chestnut flour is a gluten-free alternative to wheat flour.

Seen your first conker? Record it on Nature's Calendar

Spotting your first ripe horse chestnut seed is one of the seasonal events recorded through our Nature's Calendar project. Nature's Calendar tracks the effects of weather and climate change on wildlife across the UK, with dataset going back nearly 300 years. This allows us to get a better sense  of how climate change and other patterns in the environment are impacting nature.

By taking just a few minutes to share what you see, you'll be adding to hundreds of years' worth of important data. We couldn't do it without you!

Visiting woods

Spot the signs of the seasons

Have you seen your first butterfly or swallow of spring? Or your first ripening berry or autumn leaf tint? Let us know what's happening to animals and plants near you and help scientists track the effects of climate change on wildlife.

Join Nature's Calendar
Discover more trees, nuts and seeds