Can I Bring My Flowering Kale in for the Winter?

Growing Kale

• All forms of broccoli, cabbage, cauliflower, collards, kale and kohlrabi are variations of the same plant species, Brassica oleracea. Over the centuries, horticulturists selected mutations and developed them into vegetable crops of various forms. Collard greens and kale are most closely related within the species. All require the same ideal growing conditions: full sun, moist and well-drained fertile soil when temperatures remain between 32 and 75 degrees Fahrenheit.

Kale Temperature Tolerances

• Flowering kale plants look their best in form and color when the environment remains between 30 and 60 degrees. Kale survives temperatures down to 10 degrees without harm, but colder temps dry out and kill leaves, making them look ragged and sickly. The growing tip on the kale plant sprouts new leaves if it is not frozen. Conversely, when temperatures exceed 60 degrees, leaves tend to lose their pink or white variegation. When temperatures rise regularly above 75 degrees, the plants bolt -- the growing tip elongates and forms a gangly, upright stem with tiny yellow flowers and then dies.

Overwintering Kale

• If you garden in a region where the winter cold is too harsh for flowering kale to survive, plants may be brought indoors to enjoy. In U.S. Department of Agriculture plant hardiness zones 6 and colder, chances are the plants will be frozen and killed at some point from December to February. For longevity indoors, flowering kale plants must be placed in a sunny window where temperatures don't get above 60 degrees. This may not work well with conditions in the house. Choose an unheated sun room, enclosed patio or chilly spare bedroom that doesn't get too warm and is sunny.

Disposing of Kale

• Flowering kale plants look most attractive when the rosette of leaves remain tight and low. This condition develops in full sun and chilly temperatures. Once the growing tip elongates and bolting occurs, the lifespan of the plant is limited, even if overwintered in the house. Kale naturally grows as a biennial, being a leafy plant initially, but then bolting to flower and setting seed before dying. Flowering kale that blooms indoors will soon thereafter die and is not worth maintaining to again relocate outdoors in spring.