The Plant Man: Understanding black mustard

By Steve Kawaratani

“I had forgotten what mustard fields looked like, sheet upon sheet of blazing yellow, halfway between sulphur and celadine…” –Monica Baldwin

Click on photo for a larger image

Photos courtesy of Steve Kawaratani

Steve Kawaratani

The wet winter and spring in Laguna and beyond have been followed by a gorgeous display of native wildflowers on and within our coastal hillsides, from the bright blue Arroyo lupine and blue-eyed grass to the very red Indian paintbrush. While the celebration of spring and the return of wildflowers should be a joyous occasion, the Eurasian invader, black mustard (Brassica nigra), has aggressively blanketed our local slopes with yellow blooms and continues to be of ongoing concern.

Black mustard is introduced and is considered an invasive weed due to the fact that it is able to out-compete native plants for habitat space. The tough and vigorous plant germinates early in winter, before native plants have established, can grow more than 10 feet tall in a season, obscures sunlight with its vigorous shoots and aggressively competes with native plants for water. “Black mustard is also believed to produce allelopathic substances that inhibit the growth of native plants.”

Click on photo for a larger image

The super bloom of black mustard

Like other mustard species, it produces thousands of seeds each season that can lay in wait for more than 50 years. The plant is opportunistic as it rapidly spreads – either in disturbed areas or by fire. Mustard can act as a “fire ladder,” carrying flames to taller trees, because it is taller than natives at a season’s end. “Mustard plants themselves don’t carry fire particularly well, but in a wind-driven fire, they will burn.”

Mrs. Chavez, my fourth grade teacher, taught our class that the Franciscan padres planted mustard seeds from their homeland, to create a path of gold along El Camino Real, the road that connects the 21 California missions. More than 60 years later, that may still be hard to prove from my perspective, however, my parents did introduce me to every mission one lost holiday road trip. I appreciate their persistence more so today than in 1960.

Click on photo for a larger image

Mustard greens and flowers are tasty

I believe that the Spaniards brought mustard to the New World as a crop, much as they did with broccoli, cabbage, cauliflower and kale. And over the centuries, the plant has spread far outside the confines of mission kitchen gardens. Younger spring sprouts can be harvested and cooked like market mustard greens. They are also tangy and spicy and the flowers taste like mustard, making a tasty treat while hiking.

Is there a cautionary tale? Biologists say the mustard plant’s unchecked spread serves as an example of what can happen if an invasive species is ignored. It is part of the introduced species most wanted list to eradicate, joining Spanish Broom, artichoke thistle, fountain grass and pampas grass. While eliminating mustard will never occur, do your part and keep invasives out of your garden. See you next time. 

Steve Kawaratani has been a local guy for seven decades and likes to garden and drive the Baja Peninsula. He can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it. or 949.494.5141.