Agree - sycamore sapling (dig out if you don't want a potentially 100ft tree there!)
Second photo shows Herb Robert and the long-leaved ones are a kind of willowherb - both weeds (although the wild geranium can be pretty and is easily pulled-up if you don't like it (or the smell.))
A trowel in the hand is worth a thousand lost under a bush.
Thanks, the sycamore needs to go I think, its right next to the house is the willowherb likely to be problematic do you think? It's an area I'm planning to leave to nature really but don't want something that'll completely take over
If the willowherb is allowed to seed, it will blow all over your garden and they will pop-up everywhere (they especially seem to like my pots!) You could wait to see if it is one which produces nice flowers but many have rather insignificant flowers. They are a food plant for several moths, so if you don't mind constantly weeding them out from other areas, it would be good to keep a few (and a long way away!)
A trowel in the hand is worth a thousand lost under a bush.
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