Hi, apparently seeds of a plant had fallen into this pot and now it is full of the plant. I let the plant grow but it has recently started to attract whiteflies. I am now wondering if it is worth to keep it. I would appreciate any help for identifying this plant.

Salpiglossis, perhaps.

If the foliage is aromatic it could be Salad Rocket.

Check with images of Dysphania ambrosioides.

Thanks for your replies. I don't think it is Salpiglossis or Dysphania, though. And after Yorkshirelass's message I took a bite of a leaf and it is not arugula, either (it doesn't have any taste or flavor).
So, the mystery continues.

China Asters, Callistephus chinensis maybe?