(Brassica rapa) Members of the cabbage family, choy is a type of mustard greens native to Asia. Prone to bolt in frosty weather or summer heat, they are best in spring or fall conditions. Direct sow 1/4 inch deep, or start indoors 4-6 weeks before last frost and transplant out just after last frost. Ideal germination temperature is 75-80F. Seeds germinate in 10-14 days. Space plants 12 inches apart, in moist, rich, well-draining soil.