Why do kale

Content on WhatAnswers is provided "as is" for informational purposes. While we strive for accuracy, we make no guarantees. Content is AI-assisted and should not be used as professional advice.

Last updated: April 8, 2026

Quick Answer: Kale is a leafy green vegetable from the Brassica oleracea species, cultivated for over 2,000 years since ancient Greek and Roman times. It gained significant popularity in the U.S. during the 2010s, with consumption increasing by over 400% between 2007 and 2014 according to USDA data. Kale is nutritionally dense, providing 684% of the daily value for vitamin K and 206% for vitamin A per cooked cup (130g), while being low in calories at just 36 calories per serving.

Key Facts

Kale belongs to the Brassica oleracea species, same as cabbage and broccoli
Kale consumption in the U.S. increased by over 400% between 2007 and 2014
One cup of cooked kale (130g) provides 684% of daily vitamin K needs
Kale has been cultivated for over 2,000 years since ancient Greek times
Kale contains only 36 calories per cooked cup (130g) serving

Overview

Kale is a leafy green vegetable belonging to the Brassica oleracea species, which also includes cabbage, broccoli, cauliflower, and Brussels sprouts. Its cultivation dates back over 2,000 years to ancient Greece and Rome, where it was a common crop. During the Middle Ages, kale was one of the most common green vegetables in Europe due to its hardiness in cold climates. The vegetable was brought to North America by English settlers in the 17th century. In the 1990s, kale began gaining attention as a "superfood" due to its exceptional nutritional profile, and by the 2010s, it had become a mainstream health food with significant commercial production. Today, California produces approximately 60% of the kale grown in the United States, with the vegetable available year-round in most markets.

How It Works

Kale grows as a biennial plant that thrives in cooler temperatures, typically between 60-65°F (15-18°C), making it suitable for spring and fall cultivation. The plant develops from seeds that germinate in 5-8 days under proper conditions. Kale leaves grow in a rosette pattern from a central stem, with varieties including curly kale, dinosaur kale (also called Lacinato or Tuscan kale), and red Russian kale. The vegetable's nutritional density comes from its photosynthetic efficiency and ability to concentrate nutrients in its leaves. Kale contains glucosinolates, sulfur-containing compounds that break down into isothiocyanates when the leaves are chopped or chewed, providing potential health benefits. The plant's hardiness allows it to survive frost, which actually improves its flavor by converting starches to sugars. Harvest typically occurs 55-75 days after planting, with leaves picked from the bottom upward as the plant continues to produce new growth.

Why It Matters

Kale matters nutritionally as one of the most nutrient-dense foods available, providing exceptional amounts of vitamins A, C, and K along with minerals like calcium and potassium. Its high antioxidant content, including quercetin and kaempferol, may help reduce oxidative stress and inflammation in the body. Economically, kale represents a growing segment of the produce industry, with the global kale market valued at approximately $2.5 billion in 2021 and projected to reach $3.8 billion by 2028. Environmentally, kale requires relatively few resources compared to many crops, with lower water needs than lettuce and natural pest resistance that reduces pesticide use. Culturally, kale has become symbolic of health-conscious eating movements and sustainable agriculture practices worldwide.