Black currants (Ribes ussuriense or Ribes nigrum)
Black currants are self-sterile partly, so, it’s better to plant its two varieties close to each other.
Red currants are usually self-pollinating but in some conditions benefit from cross-pollinating with another red variety or a white variety.
In black currant (R. nigrum) almost all cultivars require insect pollination. The flowers are somewhat self-compatible, but the style and anthers are physically separated in individual flowers. However, all cultivars require insect cross-pollination to set a satisfactory crop. Self-pollinated plants have lower fertility.
Currant seeds germinate if stratified for three to four months at temperatures just above freezing. Seedlings are prolific and do not vary much from parent. Bushes grown from seed bear when two or three years old.