Plants of Southern California: Analysis Pages: Mustard (Brassica nigra and Hirschfeldia incana): How To Tell The Difference

Many people are confused about the difference between black mustard, Brassica nigra, and shortpod mustard, Hirschfeldia incana (older name was Brassical geniculata), both non-natives and quite invasive, displacing native plants. These are both somewhat variable plants, so it is indeed difficult to distinguish them at times. However, the vast majority of the time, it is very easy to distinguish them using the following characteristics:

There is a difference in the flower color, but it is impossible to use in the field unless you have both plants side by side, as in this pix from Laurel Canyon. The shortpod mustard flower, on the right, is paler yellow than the black mustard flower on the left.

I have learned that some hikers like to munch on the flowers of "black mustard", so it is of interest to know whether both species are equally edible. Fortunately, they both are. From the web:

Black mustard: "The seeds of this plant and the leaves are both edible. There are many nutritional properties of merit in Brassica nigra; for example vitamin A, vitamin B complex, vitamin C and calcium can all be found. See the full list of nutritional values for more. Black mustard is typically used as a flavoring. This plant is most frequently used fresh." (Source: Crescent Bloom) Mustard seed is commonly ground into a powder and used as a food flavouring and relish [4, 5, 17, 27, 34]. This is the black mustard of commerce, it is widely used as a food relish and as an ingredient of curry". Known Hazards: When eaten in large quantities, the seed and pods have sometimes proved toxic to grazing animals [85]." Source: GardenBed.com Shortpod mustard: "Edible Uses: Leaves; Seed. The young plant is eaten with oil and lemon juice in parts of Greece [183]. The leaves of young plants are eaten raw [61, 177]. Seeds - raw or cooked [257]. They can be ground into powder then mixed with water and eaten [257]." Source: Plants For A Future

One final comment: don't believe what you read in the floras, like the Jepson Manual, about the sizes of these plants. The heights and leaf lengths are often much, much larger than the sizes given in the floras. As a budding botanist, one of Tom's first uses of his newly-purchased Flora of Southern California by Munz was to try to figure out if the mustard in his back yard was shortpod or black. He tried to use the leaf size to discriminate them, went to his unwatered back yard and measured a leaf size that was far greater than was reported in the flora for either species.