Spring is right around the corner, which means that weeds are sprouting at many of our newest restoration sites. Not to worry, we were expecting this to happen! Invasive species management is an important part of the restoration cycle. Most project sites will require at least 2-3 years of intensive invasive removal before our native plantings grow large and dense enough to overtake the annual invaders such as mustard, radish, fennel, and iceplant.
Of all the invasive species removed by Save The Bay’s dedicated volunteers and wetland restoration staff, black mustard, Brassica nigra, is perhaps our most targeted invader. Our relationship with this plant is conflicted; though we love to see it removed from wetland areas, Save The Bay staff have also brought it into their homes to process into homemade yellow mustard for consumption as a condiment. Perhaps this behavior is a restoration practitioner’s fulfillment of Sun Tzu’s famous axiom from The Art of War:
If you know your enemy and know yourself, you need not fear the result of a hundred battles.
Because we all interact with mustard either in our kitchens, backyards, or local wetlands, it makes sense to learn a little more about it. Hold on to your pocket protectors, it’s time to get a little geeky.
More than an invasive species
Black mustard is native to the Mediterranean region of Europe, where it has been grown as a food crop for thousands of years. The shoots and stems can be cooked and consumed, while the seeds can be ground for use as a spice, cough suppressant, and treatment for respiratory infection. In addition to its culinary and pharmaceutical utility, mustard also found its way into scripture:
The Kingdom of Heaven is like a grain of mustard seed, which a man took, and sowed in his field; which indeed is smaller than all seeds. But when it is grown, it is greater than the herbs, and becomes a tree, so that the birds of the air come and lodge in its branches.
Besides being culturally influential, the Brassica genus has also contributed to our understanding of genetics. In 1935, Korean-Japanese botanist Woo Jang-choon (the Japanese translation of this name is “Nagahara U”) crossed the three “traditional” Brassicas—B. nigra (black mustard), B. rapa (turnip, Chinese cabbage), and B. oleracea (kale, cabbage, broccoli, cauliflower, Brussels sprouts)–to create three new hybrid species–B. juncea (Indian mustard), B. napus (rapeseed, rutabaga), and B. carinata (Ethiopian mustard). The artificial interbreeding of three separate, yet closely related, diploid species (each with two set of chromosomes), to create three new tetraploid species (each with four sets of chromosomes) is referred to as the “Triangle of U,” in reference to Nagahara U.
Though the Triangle of U was only a theory in 1935, it has now been confirmed by DNA mapping. The Triangle is significant in that it explains the creation (by both natural and artificial means) of many of our most important food crop species, and provides the genetic understanding necessary to prevent undesired hybridization of these species.
Next time you pull a mustard plant out of the ground or buy mustard seed in the grocery store, take a second to appreciate the scientific and cultural significance of this pesky weed, without which we would not have some of our favorite condiments and vegetable oils.