Euphorbia segetalis Field spurge
This Spurge flowers all through the year, as long as there is the occassional rain. It is thought to be a native of the Canary Islands, and is now naturalised throughout the Mediterranean and Southern Europe. It grows from 20~40cms tall and is considered a pest in places. It is found in fields, wasteland and olive groves. It has an erect stem as shown here, often red in colour. I will try to get better photos of the flower.