Bitter Apple Nightshade
Solanum incanum
Observed at a road side near Marigat, Rift Valley, Kenya, Africa. October 2010.
This is an abundant weed at roadsides and edges of farm plots across Kenya. It
thrives in part because of the sharp spines and foliage laced with toxic
alkaloids. Ubiquitous goats and cattle cannot consume it and so it grows
unchecked.
With maturity the fruits are about 3 cm in diameter and are lemon-yellow. Seeds in the fruit, which is terribly bitter, are probably spread by birds.