The appearance of a tall, central stalk topped with small, yellow buds signals that your kale plant has begun to flower. This process, known as “bolting,” is the plant’s natural transition from vegetative growth (producing edible leaves) to reproductive growth (producing flowers and seeds). While bolting signals the end of the plant’s life cycle, it does not mean the plant is ruined; it offers an opportunity for a final, unique harvest.
Understanding Why Kale Bolts
Kale is a biennial plant, meaning it typically completes its life cycle over two years, but it often bolts in its first year due to specific environmental cues. The main biological trigger for bolting is vernalization, which is the plant’s requirement for a period of sustained cold temperatures. Exposure to temperatures below 50 degrees Fahrenheit for several weeks can satisfy this requirement, preparing the plant for flowering.
Once the vernalization requirement is met, a rapid shift to warmer weather in the spring or early summer prompts the plant to send up its flower stalk. Extended daylight hours, known as photoperiodism, also contribute to the reproductive switch. General plant stress, such as inconsistent watering, overcrowding, or nutrient depletion, can also prematurely trigger bolting as a survival mechanism to ensure the plant completes its life cycle.
Harvesting and Edibility of Flowering Kale
The most common question when a plant bolts is whether the harvest is still edible, and the answer is a resounding yes. Bolting redirects the plant’s energy toward seed production, which changes the composition of the leaves. The older, lower leaves often become tougher and develop a noticeably more bitter flavor due to increased alkaloid production.
The new growth, however, offers a culinary treat that many gardeners anticipate. The unopened flower shoots and buds, often referred to as “kale raab” or “fuettes,” are highly prized. These tender shoots and florets are surprisingly sweet and mild, especially if the plant was subjected to a hard frost just before bolting. They can be prepared similarly to broccolini or asparagus, adding a delicate, slightly peppery flavor to meals.
To harvest these tender shoots, use a sharp knife or shears to cut the central flower stalk while the buds are still tightly closed and green. Cutting the stalk just above a lower leaf node can sometimes encourage the plant to produce smaller, secondary side shoots that are also edible. Harvesting the flower buds before they open into yellow flowers is recommended, as the stem can become fibrous and the flavor less sweet once the flowers fully bloom.
Post-Harvest Management and Plant Retirement
Once your kale has bolted and you have harvested the main shoot, you have a few options for managing the plant’s final stage.
Pruning for a Final Harvest
One choice is to prune the plant aggressively, cutting the main stalk down to a few inches above the soil line. This action may temporarily encourage a few small, new side leaves to grow, providing a final, small flush of harvestable greens. However, this new growth is usually short-lived, as the plant’s reproductive phase has already been initiated.
Saving Seeds
Alternatively, you can let the plant complete its journey by saving the seeds for the following season. This involves allowing the flower stalk to remain until the yellow flowers fade and are replaced by small, dry seed pods. This process takes approximately 30 to 45 days. The pods will turn light brown and dry out, signaling the seeds are ready for collection.
Plant Retirement
The most practical choice for many gardeners is retirement, which means removing the bolted plant entirely. Once bolting begins, the plant’s energy is no longer focused on producing the large, tender leaves you desire. Removing the plant frees up valuable garden space, allowing you to prepare the soil and plant a new crop, known as succession planting, to maximize your garden’s output.