Choy Sum Seeds,
Purple

Purple choy sum is a cool-season crop that should be planted in early spring or late summer to fall. In regions with mild winters, it can be grown throughout the cooler months. Optimal growing temperatures range between 60 F to 80 F. For those in frost-prone areas, it's advisable to plant after the last frost in spring or in late summer for a fall harvest​.

Sow Purple choy sum seeds directly in the garden about 1/4 inch deep, spacing them 4–6 inches apart in rows that are 12–18 inches apart. If starting indoors, transplant seedlings once they have at least four true leaves.

Purple choy sum requires regular watering to keep the soil consistently moist but not waterlogged. A well-balanced fertilizer or compost should be incorporated into the soil at planting to provide essential nutrients. The plant grows quickly, and you can start harvesting when it reaches about 6–12 inches in height.

Like bok choy, Purple choy sum is an annual, completing its life cycle in one year. To avoid selecting bolt-prone plants, don't save seeds from prematurely bolted ones. Let plants mature fully, harvest the dried pods, crumble the small round seeds into a jar or bag, then seal and store the seeds in a cool, dark, dry place. Choy sum cross-pollinates with other rapa species but not with different species of Brassica, so it's safe to grow it next to mustard greens (Brassica juncea), for example. To ensure seed purity, isolate your bok choy from other blooming B. rapa by about a half mile or use caging techniques. Allow your healthiest plants to flower for a strong, diverse seed pool. This is particularly useful for gardeners looking to grow Purple choy sum in successive seasons​.