What are these gigantic weeds!?

[Naga]

I cannot believe I never saw these! They are up to 6/6.5ft tall, jagged leaves and thick spikey stems which have red patchy parts. They also have some yellow flowers on top like ragwort. At first I thought they were giant hogweed but then saw the yellow flowers.

[Plot70]

That looks like a sow thistle of some kind. Some species can get quite large.

[ameno]

Yeah, that's sow thistle. It's not actually a true thistle, but an annual more closely related to dandelions. You'll find that the stem is hollow, and both the stem and the leaves exude a milky sap when broken. The leaves are actually edible, although a little bitter.

Also, if you had giant hogweed, you would know, believe me. It grows up to 15 feet.