Ruderis plants are nice to have on hand if breeding is your thing. But to smoke a pure ruderalis? No thanks.
FractalMe is spot on. They are native to an area of Russia where the natural photo-period is irregular and as a result these plants flowering cycle is dependent on age, not photoperiod. Ideally, Auto-flower strains have the flowering characteristics of Ruderalis, and the medicinal qualities of the other parent. This can be beneficial if you need a quick harvest, some finish in as little as 60 days from seed. Yield takes a major hit but often times the bud is extremely potent.