Collard greens are a popular, nutrient-dense leafy vegetable enjoyed in cuisines around the world, particularly in the Southern United States. Collard greens come from the plant species Brassica oleracea, which is the same species that gives rise to a surprising variety of common garden vegetables. This species is responsible for the large, tender leaves harvested for consumption.
The Botanical Identity of Collard Greens
Collard greens belong to the Brassicaceae family, commonly known as the mustard family. Within this family, the plant falls under the genus Brassica and the species Brassica oleracea. The specific type of Brassica oleracea that yields collard greens is categorized as a cultivar group, most often referred to as the Acephala Group. The name “Acephala” is derived from Greek and means “without a head,” defining the plant’s growth characteristic compared to headed cousins like cabbage. Collard greens are loose-leafed cultivars, specifically bred to produce abundant foliage rather than a tight, compact head.
Collard Greens and Its Kin
The fact that collard greens share the species name Brassica oleracea with so many distinct vegetables is due to the concept of a cultivar. This single wild ancestor has been subjected to centuries of selective breeding, resulting in dramatically different plant forms classified as the same species. These different cultivars were intentionally bred to emphasize a particular part of the plant, such as the stem, the leaves, or the flower head. Collard greens are the genetic kin of several familiar vegetables. For example, cabbage was bred for its terminal bud, resulting in a dense head of leaves, while Brussels sprouts were selected for their lateral buds forming small, edible miniature heads.
Cauliflower and broccoli were developed to favor the flower clusters, creating the familiar edible florets. The leafy vegetables in the species, such as kale and collards, are closely related and both fall into the Acephala Group, meaning they were bred to produce loose, edible leaves. Over time, breeders focused on different leaf characteristics, leading to the broader, smoother leaves of the collard green as opposed to the ruffled structure of many kale varieties.
Distinctive Growth and Appearance
The collard green plant possesses a physical structure that sets it apart from its many cousins. Unlike cabbage, the collard plant does not form a compact head of leaves, instead growing as a rosette of large, individual leaves on a robust, upright central stalk. This sturdy stem can grow quite tall, with some varieties reaching heights between two and six feet. The leaves themselves are typically a dark, sometimes bluish-green color, and are characterized by a smooth, broad texture. These large leaves are the primary harvest, gathered progressively from the bottom of the plant upward.
While the plant is botanically a biennial, meaning it flowers and sets seed in its second year, it is typically grown and harvested as an annual crop. Collards are also resilient to cold weather, a trait shared with other Brassica oleracea varieties like kale. They are considered cool-weather plants and are often planted in late summer or fall for a winter harvest, especially in warmer climates. The leaves of the collard plant are known to develop a milder, sweeter flavor after exposure to frost, which can be tolerated down to temperatures as low as 15 degrees Fahrenheit.