Around the beginning of August each year, invasive European or "common" buckthorn (rhamnus cathartica) berries begin to ripen. As seen in these photos, the females produce dense clusters of fruit, which change from green to purplish black. Once the drupes are ripe, they are viable and ready to spread. Buckthorn colonizes by dropping its seeds straight down to form a thicket, and creates new infestations using birds. Unfortunately for the birds, there is no nutritional value i