What plant is this?

Question

This plant has suddenly shown up in our garden and it’s REALLY REALLY fast growing !!
Any idea what it is? I’m getting worried

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Answer 1

This looks to be a Horse Chestnut. Likely growing where a squirrel or chipmunk planted it!

https://www.gardeningknowhow.com/ornamental/trees/horse-chestnut/how-to-grow-a-horse-chestnut-tree.htm