Cape sorrel (Oxalis pes-caprae, also known as Bermuda buttercup) is blooming rampantly across the countryside these days. It’s not native, having been introduced to Malta around 1806 and spreading from there. Within 50 years it carpeted the Mediterranean region, cheering up fields and wasteland everywhere. The flowers only open when the sun is shining, resulting in entire hillsides that are green in the morning, and completely yellow in the afternoon.
I love this little plant, native or not.
(Photographed growing from a stone wall beneath an olive tree. Click the image to biggify.)