Species Profile: Field Mustard

Imagine walking around the Newport Beach Back Bay in sunny southern California in late December.  The cool breeze from the ocean is pleasant, the bright sun is warm on your sunblocked face, and the rocky and sandy landscape is covered with small shrubs, although the soil is still visibly dry.  You check back in after the “winter” rain passes through and the same rocky and sandy soil is now covered with little green rosettes that have quickly sprouted after the recent dose of precipitation.  A few weeks later, you return, and those same plants have bolted and flowered.  They’re growing like weeds, can be as tall as or taller than you, and produce hundreds of seeds per plant!  The predominant species you’re seeing is Brassica rapa, commonly known as the field mustard.  It will grow almost anywhere, under a large variety of conditions, and are cultivated for agriculture (cultivars include turnips and canola), but the ones you see are wild and invasive.  It is unclear how B. rapa was introduced from the old world, but it can now be found in all of the United States.

Brassica rapa Back Bay Newport Beach, CA
The Back Bay in Newport Beach, CA at the end of the Brassica rapa growing season. Photo credit: Art Weis

Agricultural and scientific importance

An annual plant, B. rapa has famous relatives such as the plant “lab rat” Arabidopsis thaliana and Brassica oleracea which is the cultivated species that gives rise to broccoli, cauliflower, brussel sprouts, cabbage, bok choi, and kohlrabi among others.  The large number of Brassica species is indicative of the great genetic diversity, and such genetic diversity enables organisms to adapt to novel environments and evolve in response to changing environments (both very handy for invaders!).  For example, a previous study utilized the resurrection paradigm to demonstrate that in the face of changing precipitation patterns, populations of B. rapa were able to genetically respond in a few years and evolved a significantly different shorter flowering time in response to drought.

Identifying Brassica rapa

Brassica rapa is characterized by pinnate and hairy rosette leaves close to the ground, a stalk with clasping leaves, and cluster of flowers at the terminal branches.  The individual flowers have four yellow petals and characteristic of the Brassica family, has four stamen and two staminodes.  Fertilized flowers lose their leaves and the carpel elongates to form pods or siliques filled with seeds.  Though B. rapa is cultivated for its thick taproot, wild varieties can be harvested for their rosette leaves or flower buds.

Brassica rapa inflorescence on the primary axis. Photo credit: Steven Franks

Eating the mustard family

The mustard family has evolved to produce a class of organic compounds called glucosinolates.  It is a natural pesticide which makes insect herbivory low, but to humans who consume glucosinolates at low levels (relative to body size), it can be a desirable flavor!  Check back soon to see how I harnessed the flavor of field mustard.

Sheina

A self-proclaimed modern day nomad, I was born in the Philippines, grew up in southern California—lived all over really—and now I do research as a graduate student in Indiana and the Pacific Northwest. Professionally speaking, my current area of focus is speciation and ecological genetics and genomics, and a common theme in my various projects over the years is evolution in agricultural systems. As a recipient of a GLOBES—an interdisciplinary program funded by the National Science Foundation (NSF) through the Integrative Graduate Education, Research, and Traineeship grant (IGERT) —fellowship, I have received training which has better enabled me to view and ponder topics without my science hat on. I take great joy in eating, cooking, and experiencing nature through various activities. I love to travel and anticipate many local and international invasivore field trips! Though my research interests do not directly involve the study of invasive species, I have had my fair share of negative encounters with environmentally noxious organisms in the midst of doing field research. I carry around a machete with which to combat my gnarly “Himalayan” foes, and my machete and I have raised more than a few eyebrows. Apart from my personal vendetta against these deliciously juicy pests, I feel that there are great advantages to linking our awareness of the natural world to our culture, and Invasivore is an avenue to do just that. I feel that an increase in general knowledge of invasive species will be of great benefit to the field of invasive species and conservation biology. Knowledge and awareness will lead to action, and action will lead to results!

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