Cabbage, scientifically known as Brassica oleracea, is a common vegetable whose edible portion is a dense, leafy head. Like all plants, cabbage produces seeds to complete its life cycle. However, the seeds are not found within the tight, coiled head that is harvested and eaten. This is why most consumers never encounter the seed-bearing structures, which only appear long after the edible part of the plant has been removed.
The Cabbage Life Cycle and Bolting
Cabbage is classified as a biennial plant, meaning it naturally requires two full growing seasons to progress from a seed to a seed-producing stage. The first year is dedicated to vegetative growth, during which the plant develops the large, compact head of leaves that is typically harvested for food. If the plant is not harvested and survives the winter, it enters the second phase of its life cycle.
This transition requires a process called vernalization, a period of sustained cold temperatures, often below 50°F for several weeks, which triggers the plant’s reproductive phase. After this cold exposure, and as temperatures warm in the spring, the plant begins to “bolt.” Bolting is the rapid elongation of the central stalk, which shoots up from the core of the leafy head.
This dramatic growth signals the plant shifting its energy from leaf production to reproduction. Commercially, bolting is avoided by growers because it makes the head bitter and inedible. However, it is a necessary biological step for the plant to ultimately flower and create viable seed.
Physical Location: Finding Seeds on the Plant
Once the central stalk has elongated, it develops numerous small, four-petaled flowers, which are typically bright yellow. These flowers require cross-pollination from another cabbage plant, usually by insects, to set seed.
Following successful pollination, the flowers give way to slender seed pods called siliques. These pods are the direct location where the seeds are formed and matured. Initially green and fleshy, the siliques gradually dry out and change color as the seeds inside ripen.
As the siliques mature, they turn a light tan or brown color, becoming brittle and papery in texture. Inside each dried pod are small, round seeds, typically dark brown or black. Seed savers must harvest the pods before they become fully dry and split open, releasing the seeds.
Practical Seed Sourcing and Storage
For the average gardener, acquiring cabbage seeds commercially is the most reliable method, bypassing the need to wait two years for a plant to produce its own. When sourcing seeds, it is important to distinguish between open-pollinated (OP) and hybrid (F1) varieties, especially if the intention is to save seeds for future planting.
Open-pollinated seeds, which include heirloom varieties, will produce plants that are consistently “true-to-type” from one generation to the next. Hybrid (F1) seeds are the result of a controlled cross between two specific parent plants, offering desirable traits like uniform size or disease resistance in the first generation.
Saving seeds from an F1 hybrid is unpredictable, as the resulting plants in the next season will likely revert to the varied characteristics of the original parent plants. Therefore, home seed savers should focus on open-pollinated varieties to maintain consistent characteristics.
To store saved or purchased seeds effectively, they must be thoroughly cleaned and dried to prevent mold and maintain viability. Cabbage seeds should be stored in a cool, dark, and dry environment, typically in an airtight container, where they can remain viable for several years.