Cabbage plants do produce seeds, though these seeds are not found within the edible head that is typically harvested for consumption. This article will explain how and when cabbage plants produce seeds, what these seeds look like, and how they can be used for planting.
How Cabbage Produces Seeds
Cabbage (Brassica oleracea) is a biennial plant. During its first year, the plant forms the dense, leafy head that is harvested as a vegetable. If the cabbage plant is left unharvested and allowed to continue growing into its second year, it will transition from vegetative growth to reproductive growth.
This transition to seed production is known as “bolting.” Bolting occurs when the plant sends up a tall, central flower stalk. Environmental factors such as prolonged cold temperatures below 50°F (10°C) during early growth, followed by longer daylight hours, can trigger this process. Additionally, high temperatures, often above 80°F (27°C), or even significant temperature fluctuations and stress, can also induce bolting.
Once the flower stalk develops, small, yellow flowers will bloom along it. These flowers are pollinated, which then leads to the formation of long, slender seed pods, known as siliques. The seeds mature inside these pods, drying and turning brown as they ripen. For seed saving, pods should be fully dry and brown.
Identifying Cabbage Seeds and Sourcing Them
Cabbage seeds are small and typically round, ranging in color from dark brown to black. They are similar in appearance to the seeds of other plants within the Brassica family, such as broccoli or kale.
For home gardeners or those looking to grow cabbage, seeds are typically purchased from specialized sources. These include local garden centers, various seed suppliers, and online retailers. These suppliers offer a wide range of cabbage varieties, including heirloom, hybrid, and organic options, ensuring seeds are viable and ready for planting.
While it is possible to save seeds from home-grown cabbage, this process requires allowing the plant to complete its full biennial life cycle, which means letting it bolt and mature beyond the typical harvest stage. This often involves overwintering the plant. Additionally, to ensure the purity of the cabbage seeds, especially if growing different Brassica species nearby, isolation measures are often necessary to prevent cross-pollination.
Growing Cabbage from Seed
Growing cabbage from seed provides a rewarding experience. Seeds are commonly started indoors about six to eight weeks before the last anticipated spring frost date in your region. Cabbage seeds germinate best when the soil temperature is consistently between 70°F and 75°F (21-24°C).
Seeds should be sown shallowly, about 1/4 inch deep, in a quality seed-starting mix. After germination, providing ample light is important to prevent seedlings from becoming leggy. Once the seedlings have developed three to four true leaves and are approximately 4 to 6 inches tall, they are ready for transplanting. It is advisable to harden off the seedlings by gradually exposing them to outdoor conditions for about a week before planting them permanently in the garden.
Cabbage thrives in cool weather, with optimal growing temperatures ranging from 40°F to 70°F (4-21°C), and requires at least six to eight hours of full sunlight daily. The plants prefer fertile, well-drained soil that is rich in nitrogen. When transplanting, space cabbage plants 12 to 24 inches apart, with rows two to three feet apart; closer spacing can result in smaller heads. Consistent moisture is also important for healthy growth, so ensure the soil remains evenly moist but not waterlogged.