The leaves were the most noticeable thing about the plant, with large spikes protruding from the main veins. The fruit was colored similarly to a watermelon and it was between the size of grape and a plum. I didn't see any open flowers, but photo 4 shows a bud. The buds were hairy just like the leaves.
Grassy, disturbed area that looked like a horse trail. Payne's Prairie Preserve State Park
Considered a noxious weed. Spread by livestock and wild animals.