It's one of the camelia bushes, rendered antique. I've been rereading Mrs Dalloway - I have to write a piece on the presence of the Victorian in it and in To the Lighthouse, and as ever, reading with an eye to one particular angle makes one read differently (there are, I'd point out, though I know I'm not alone in noticing this, a lot of Victorian commemorative statues in the novel). And there are a lot of leaves. Rezia, for example, puts a hand on Septimus's knee as they sit in Regent's Park, "so that he was weighted down, transfixed, or the excitement of the elm trees rising and falling, rising and falling with all their leaves alight and the colour thinning and thickening from blue to the green of a hollow wave, like plumes on horses' heads, feathers on ladies', so proudly they rose and fell, so superbly, would have sent him mad." Leaves can do strange things to one, in other words.
I'm trying hard to think how to work in to another piece the fact that Ethel Lang, the very last person alive who'd been born in Victoria's reign died yesterday, aged 114. Somehow that makes me feel much older, suddenly.