Both are easily burned by intense sunlight. Leaf size and number is reduced under water stress. Currant flowers are borne toward the bases of one-year old stems and on spurs on older stems. They appear in early spring with new growth. The strig length is reduced or flowering is suppressed by lack of winter chill.
Pollination is by hoverflies and other insects.
Black currant flowers also attract honeybees. To increase both fruit size and number, clip off part of the ends of the strigs while the bushes are flowering. Depending upon the cultivar, fruits ripen from 70 to 100 days after blossoming. Black currants commonly ripen from the top down, encouraging birds to strip berries as they color. Modern red currant varieties have been selected for their ability to ripen all the berries on a strig at once.