Ornamental cabbage and kale, both cultivars of Brassica oleracea, are cool-weather additions that provide color when most other garden plants have faded. They are distinct from their edible relatives, having been bred specifically for their vibrant, rosette-like foliage in the autumn and winter landscape. Their leaves showcase patterns of white, pink, rose, red, and purple, often intensifying in color as temperatures drop. This unique appearance prompts the question of whether this bedding plant will return reliably year after year.
Defining the Life Cycle
Ornamental cabbage is botanically classified as a biennial, meaning its complete life cycle spans two growing seasons. During the first year, the plant focuses exclusively on vegetative growth, developing the dense rosette of colorful leaves. The plant must then undergo a period of cold exposure, called vernalization, before it can transition to its reproductive phase.
Flowering and seed production occur only in the second growing season, after the required chilling period. In horticulture, ornamental cabbage is treated as an annual, planted for a single season of display and removed once the weather warms. Since it dies after producing seeds and does not live for multiple years, it is not considered a true perennial.
Optimal Growing Conditions
The plant’s foliage display is dependent on cool conditions, making it a favorite for fall and winter gardens. Optimal performance and the most vivid coloration occur when temperatures are consistently below 60°F (15°C). The pigments responsible for the colors are enhanced following exposure to frost.
Ornamental cabbage prefers full sun, which helps maximize its compact shape and color intensity. In warmer climates, partial afternoon shade can prevent the plant from becoming stressed. It requires organically rich, well-drained soil that is kept consistently moist.
Managing Overwintering and Seed Production
While the plant can survive winter in USDA hardiness zones 7 to 11, its ornamental value is eventually lost. The plant can tolerate temperatures as low as 5°F once acclimated, but survival into the second year triggers reproduction. Vernalization ensures the plant is large enough to support a second season of growth and seed production.
Once the chilling requirement is met and the weather warms, the plant will “bolt.” Bolting is the rapid vertical elongation of a central flower stalk, the plant’s final attempt to produce seeds. This stretching and subsequent flowering ruins the appealing rosette form, ending its use as a decorative plant.