sensa

What is this plant?

Thanks for the responses, and thanks for that ^ link chilli lover, I was panicking slightly earlier, but what you have identified it as is correct, there is the dark blotch in the centre of the leaves as seen here.

What is this plant?

On closer inspection, my worst thoughts were confirmed. It is knotweed. As they are young plants, and the soil was good quality topsoil, could it have been a rhizome in the topsoil? If so would I have any recourse?

Any tips on how to treat knotweed? There are no big roots underneath these plants. 

What is this plant?

Hi All, new to the forum and new to gardening. Planted out some sunflower seeds at the beginning of the summer, and have had these spring up, me thinking they were sunlowers at first, now I'm not so sure?
I planted some orange multi stemmed ones and some pale yellow ones?
Any ideas? 

What is this plant?