Grow Cabbage, Broccoli and Kale from Seed
For a late spring or early summer harvest, start these seeds indoors 4 to 6 weeks before the last spring frost. Jump start the season by as much as 30 days with the help of cold frames, cloches and row covers.
Plant seeds ¼ inch deep in a quality seed starting or planting mix. Place in a warm location and keep the planting mix moist but not soggy wet.
Move the containers to a sunny window or under artificial lights as soon as any green appears. Continue to grow broccoli, cabbage and kale seedlings indoors with temperatures of 55-65 degrees.
Save some seeds to plant in mid-summer or early fall for a fall or winter harvest.
A bit more information: Winter sowing is another option for starting these and other seeds indoors. All you need are some plastic milk jugs or soda bottles, potting mix and seeds. No artificial lights or daily care is needed.