Cabbage plants do flower, a process known as “bolting.” While a natural part of the plant’s life cycle, this is generally undesirable for gardeners cultivating cabbage for its edible head. Bolting indicates the plant shifts its energy from producing the dense leafy head to developing flowers and seeds.
The Cabbage Flowering Process
When a cabbage plant bolts, its growth habit changes significantly. Instead of forming a compact head of leaves, the plant sends up a tall, central stalk from the head’s middle. This stalk can reach 1.5 to 2 meters (5 to 6.5 feet) and develops small, yellow, cruciferous flowers.
This transition signifies a shift from vegetative growth (head formation) to reproductive growth (seed production). Once bolting begins, the cabbage head’s quality diminishes. Leaves often become tough, woody, and bitter, making the primary harvest less palatable or unusable.
Why Cabbage Flowers
Cabbage is a biennial plant that naturally flowers and produces seeds in its second year. However, it is often grown as an annual, harvested in its first season. Premature bolting typically responds to environmental or physiological stress, accelerating the plant’s reproductive cycle.
Temperature fluctuations are a primary trigger. Prolonged exposure to cold temperatures (below 10°C or 50°F) during the seedling stage, followed by warmer weather, can initiate flowering (vernalization). High temperatures during head formation can also stress the plant and cause it to bolt. Other stressors include inconsistent watering, nutrient deficiencies, or root disturbance from transplanting. Some cabbage varieties are also genetically more prone to bolting.
Dealing With Bolting
To minimize bolting, several preventative measures can be taken. Selecting bolt-resistant varieties is a practical first step, as some cultivars are specifically bred to be less sensitive to environmental triggers. Planting cabbage at the appropriate time of year, typically in spring or fall, avoids extreme temperature swings during critical growth phases.
Providing consistent moisture and adequate nutrition helps reduce plant stress, which can otherwise lead to premature flowering. Using row covers offers protection from sudden cold snaps, and mulching helps regulate soil temperature, keeping roots cooler. Harvesting cabbage heads at the right maturity before their natural reproductive cycle begins can also prevent bolting.
If a cabbage plant does bolt, the main head’s quality will likely be compromised, often becoming bitter or tough. However, the outer leaves around the developing flower stalk can sometimes still be eaten if harvested quickly, before bitterness intensifies. The flower stalks and young, unopened flowers are also edible and can have a milder, sweeter flavor than the bitter head, similar to broccoli rabe. These parts can be used in various dishes, such as stir-fries or steamed preparations. Alternatively, if seed saving is desired, the plant can be left to complete its flowering and seed production cycle.