Can you eat conkers? Safety advice and chestnut differences

Glossy, smooth and perfect for a game of conkers, the much-loved seeds of the horse chestnut tree are a familiar sight across the UK in autumn. But how much do you know about them? Read on to uncover some fascinating facts, how to tell horse chestnut and sweet chestnut trees apart, and what you can safely do with your conker collection.

Can you eat conkers?

No, you can’t eat conkers. They contain several natural chemicals which are poisonous to humans, including a toxin called aesculin. While eating a conker is unlikely to be fatal, it could make you ill.

Are conkers poisonous to dogs?

Yes, conkers are poisonous to dogs as well as cats and most other animals. If eaten, they can cause vomiting, diarrhoea and abdominal pain among other symptoms. Conkers can also cause blockages due to their large, round shape. So it’s important to keep a close eye on your dog during autumn walks and see a vet if you’re concerned about something they’ve eaten.

Curiously, conkers are also believed to be poisonous to horses despite the tree bearing their name. However some animals, such as deer and wild boar, can consume conkers without harmful side effects.

What is a conker?

Conkers are the seeds of the horse chestnut tree. They are large, round, brown and glossy. They grow in spiky green cases which fall to the ground when ripe.

Be careful not to confuse them with chestnuts, which are the edible seeds of the sweet chestnut tree.

When do conkers fall in the UK?

Conkers ripen in autumn and usually fall to the ground in September and October, although this can happen earlier if the summer has been hot and dry.

Look for them scattered around the base of horse chestnut trees. The outer case often splits open on impact, revealing the shiny conker inside. Listen out while you’re exploring too – you might hear a soft thud as they hit the ground!

Tell us about your first find of the season

Did you know spotting your first ripe conker is important for science? We gather records of the changing seasons to track the effects of climate change on trees and wildlife. Discover how your family can help us with our Nature's Calendar project.

What's the difference between horse chestnut and sweet chestnut?

It might surprise you, but horse chestnut and sweet chestnut trees aren’t related. Horse chestnut belongs to the soapberry family, while sweet chestnut is part of the beech family.

They're both large trees, but their leaves don't look the same. Horse chestnut has palmate (hand-shaped) leaves made up of five to seven leaflets, while sweet chestnut has long leaves with serrated edges.

Although their seeds are similar, there are some big differences. Both grow in green shells, but horse chestnut cases are covered in short spikes while sweet chestnut cases have lots of fine spines. Inside the shells, sweet chestnuts contain two or three teardrop-shaped nuts while round, glossy conkers are usually singular.

The biggest difference is that sweet chestnut seeds are edible, unlike conkers. Roasted chestnuts are a popular Christmas dish, while chestnut flour is a gluten-free alternative to wheat flour.

How did the horse chestnut tree get its name?

In 1664, John Evelyn wrote about horse chestnut trees in his book Sylva. He suggested they were named after their use as a cure for horses with breathing problems and coughs.

Things to do with conkers

If you're anything like us, you probably end up with a sizeable conker collection each autumn. Their glossy sheen and tactile shape make them irresistible to children and adults alike!

But what can you do with them? Well, there's the traditional game of conkers, where two players battle to defeat their opponent with a conker tied on the end of shoelace. They're also handy for numerous crafts and can even be used for maths homework!

• Painting – dip conkers in brightly coloured paint and roll them around a canvas to make autumn art.

• Models – use cocktail sticks to join conkers together and make fun models.

• Jewellery – string conkers onto a shoelace to make a bold bracelet or necklace.

• Maths – kids can practise counting, sorting and weighing with their prized conkers.

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 data 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!