I set up an experimental seed starting tray, but can' remember exactly what seed I put for some seedlings. One of them is a HUGE seedlings pictured in photos below.
I just vaguely remember that it could be an Agastache, or so some form of mentha.
I think this is the second one of the same kind, just at the early stage of development:
Update:
It turns out it was Cucurbita pepo - decorative pumpkin. Out of 8 seeds, 2 germinated. Those two seedlings are now in their own containers:
You may have noticed that a cotyledon of the smaller seedlings is whorled. I posted a separate question on that: Why is my pumpkin seedling's cotyledon twisted and whorled?
Update 2:
I already thought there will be no more pumpkin seedlings, but two more appeared this afternoon - boy, they are moving earth: