Why Does Ornamental Kale Look Better in Cold Weather?

Ornamental kale and cabbage bring color to the garden as the weather cools. Their pink, purple and cream centers become more noticeable after a stretch of cool nights.

In warm weather, green chlorophyll masks the colors in the center of the plant. After several nights below about 50°F, the leaves lose chlorophyll and those colors become visible.

UMass Extension says full color takes two to four weeks of cool nights. A plant that looks mostly green at a garden center in September may look its best in mid-November.

Ornamental kale and cabbage belong to the same species as cabbage and broccoli grown for eating. They also share that tolerance for cold.

NC State Extension and University of Wisconsin Extension list them as hardy to about 5°F once they have adjusted to cooler weather. A frosty morning does not harm these adjusted plants, and they often stay attractive into December.

Ornamental kale and cabbage are the same species. Their leaf shapes are the main difference.

The word “flowering” on a label refers to the colored center, not actual blooms.

• ✓ Choose the size and color you want. Buy plants that are nearly colored. They will not grow much after planting, especially if their roots are crowded in the pot.
• ✓ Plant a little deep. Bury the stem so the lowest leaves sit at the soil surface.
• ✓ Provide sun and water. Plant in full sun and keep the soil moist until the ground freezes.
• ✓ Stop fertilizing when nights turn cool. Extra nitrogen during the coloring weeks can keep leaves from coloring well.
• ✓ Pair with pansies. In a container, place one kale or cabbage in the center and surround it with pansies.

These plants are biennials, meaning their life cycle spans two growing seasons, but they are usually grown for one season. Plants that survive winter produce small yellow flowers in spring, stretching out their compact shape. Most gardeners remove them in spring and plant fresh ones the following fall.

The leaves are edible but more bitter than kitchen kale. They turn gray when cooked and are generally used as a garnish.

Reference: UMass Extension, “Flowering Cabbage and Kale”; NC State Extension Gardener Plant Toolbox, “Brassica oleracea (Ornamental Kale Group)”; University of Wisconsin–Madison Extension, “Ornamental Cabbage and Kale.”