Here is a picture of the "flowers"

It's Dorstenia elata. If you google images you'll find this one and more info on it. In warmer climates it is regarded as a bit of a pest (though a very slow-growing one). The seeds form in that flower "pad". We used to call them "mattress button plants" though that's the danger of common names.
Dorstenia is a really interesting group of plants.... and yours is a really tough one.

Here is a link that might be useful: Dorstenia