um, it is definately some kind of thistle, burdock or carline thistle maybe. There are several thistles grown as ornamentals such as onopordum, silybum (milk thistle) cynara (cardoons) and cirsium but I don't recognise yours as an ornamental. You could let it flower and decide whether you like it or not (the defintion of what is a weed is notoriously subjective with no rules apart from the very general - a weed is a plant in ther wrong place.

thith-ul ... if you lithp ... named after Thith-ul B. DeMille, i think ...

the fact that you did not plant it under the rock.. is a good indication that it is a weed.. which is defined as ANYTHING you dont want in your yard ...

let me guess.. how far from the bird feeder???

it will slice you open like there is no tomorrow .. its one of the mean ones .. or really hurt kids feet if stepped on ..

but if that can be avoided... it is a truly marvelous show in fall.. when the finches go nuts over it.. hanging upside down to get at it all ...

your choice..

ken