Mustard greens are one of the few vegetables more celebrated in culinary circles for their seeds than their leaves.

Western cooks have been tinkering with brown mustard seeds since the time of the Romans, who figured out they could produce an excellent condiment by mixing crushed seeds with unfermented grapes. While ancient mustard recipes calling for ingredients as varied as almonds, pine nuts, honey, lovage and fish sauce are today considered kitchen oddities, every bottle of Grey Poupon harks back to the Roman fondness for ground mustard seeds. They first exported seeds to Gaul, the region encompassing modern-day France in the 10th century. By the 1200s, the city of Dijon was in the mustard-making business.

But mustard greens are more than their seeds. Here, seven more things to know about the cruciferous vegetable:

1. Mustard greens are sometimes called Indian mustard or Chinese mustard, names that reveal the 5,000-year-old plant's Asian ancestry. Native to India, the first advances in mustard green cultivation, meaning the growers pioneered different varietals, occurred around Sichuan, China. Ya cai, or preserved mustard greens, remain an important seasoning in Sichuanese cuisine.

2. Mustard greens have long played an important role in Southern cooking, but they're increasingly prized out west as “green manure.” When chopped and left in the field as ground cover, greens suppress weeds; promote soil fertility and release biotoxic compounds that may help repel pests. Preliminary studies conducted on Washington State potato fields showed an application of mustard greens could reduce nematodes by 80 percent.

3. According to “The Oxford Companion to Food,” in the Middle Ages, the staff roster of European royal courts and monasteries often included a person who was tasked exclusively with growing and making mustard. He was known as the mustardarius.

4. When the USDA last tallied statistics for leafy greens by individual crop, South Carolina was third on the list of top mustard green-producing states. It didn't take too many messes of greens to earn the honor: South Carolina farmers in 2001 planted 700 acres, resulting in a harvest that accounted for 11 percent of the nation's total.

5. There are many different kinds of mustard greens, distinguishable by their leaf size, edging style and color, which can range from garnet red to dark purple. Most mustard greens sold in the U.S. are bright green. When buying greens at the supermarket, look for vivid emerald leaves without any yellow or brown spots.

6. Phenomenally nutritious, mustard greens are an especially good choice if you're looking to bump up your intake of vitamin K. One cup of cooked mustard greens provides 922 percent of your daily recommended allowance. The vegetable is also credited with lowering the risk of cancers, including breast cancer, lung cancer and prostate cancer.

7. “The Foods and Nutrition Encyclopedia,” published in 1993, sadly reported the national production of frozen mustard greens hadn't budged between 1969 and 1990, even though the overall production of frozen vegetables climbed 65 percent during the same period. “The raw vegetable has a very distinct mustard flavor,” the editors wrote. “This may be why the popularity of the fresh vegetable has declined somewhat in favor of collards, kale and spinach.” To mellow the greens' distinctive pungency, food writer Molly Watson recommends blanching them in salted water for a minute or two before cooking. Soy sauce, olive oil and sesame oil can also help tame the bitterness.