Urtica cannabina (U. cannabina), a member of the Urticaceae family, is widely distributed throughout the temperate regions of the world and can be used as a nutritious feed for animals through the winter period. To provide high-quality forage all year-round, we treated freshly harvested U. cannabina without additives (control), but with corn flour (CF) (5:1 w/w), molasses (2, 4, and 8% fresh weight), or LalsiL Dry (LD) inoculant (5, 10 and 20 mg kg−1 of fresh weight). We then assessed the chemical composition, in vitro digestibility and fermentative parameters of the products after 0, 3, 5, 15, 20 and 60 d of ensiling. The results showed that: (i) U. cannabina had large quantities of protein and some essential minerals, including calcium, potassium, sodium, zinc, copper and manganese, and was particularly rich in magnesium and iron. (ii) U. cannabina can be preserved as a highly nutritious silage. No additive treatment or the LD inoculant treatments produced badly preserved silages. The 2% molasses treatment produced badly preserved silage, but 4–8% molasses produced well-preserved silages. The CF treatment also produced well-preserved silage. We recommend the application rates of molasses at 4–8% of fresh weight or 5:1 CF to improve U. cannabina silage.