Northern Africa; Middle East (Mediterranean); Cyprus, Egypt; Europe (Ireland to Italy) (USDA GRIN). GBIF shows similar distribution with concentration of observations in south France and Spain, but many throughout Europe.
"S. verbenaca is a tall perennial herb with hairy stems and branches that erectly sprawl out. Its leaves are basal and toothed that vary from 3 to 10 cm (1.2 to 3.9 in) long. It has soft purple to violet flowers in mid summer. It is in flower from June to September, and the seeds ripen from July to October. The flowers are bisexual and are pollinated by bees. Some are also cleistogamous and pollinate themselves." (Wikipedia)
Not in Sunset Western Garden Book. Seems to be available online.