Largest seedling

The large seedling that I thought might be an ash tree appears to be something else, though it is still too early to tell what. The leaves are a rather olive green and the bud in the centre is red, not typical of an ash. I think it might be an exotic.

Seedlings appear almost every day now and by the end of the year I should have a fairly fully vegetated window box with a surprising variety of species - gardening by serendipity.