Invasive Species Threatens Los Osos
Help Us Kill This Monster!
Yes, sewer construction is over, the holes are covered and the streets are resurfaced, but the project has left behind an insidious reminder. The digging up of practically every street in Los Osos/Baywood Park has engendered a huge crop of Sahara mustard, Brassica tournefortii.
Numerous Old World mustards have invaded North America. Of these Sahara mustard is the newest and by far the worst. It really is a monster! It is a robust, fast-growing, drought-tolerant winter annual that prefers sandy soils. The basal rosette of divided hairy leaves can span three feet in wet years. The nearly leafless flowering stems branch profusely and grow to a height of about two feet, creating the appearance of a shrub from a distance.
These highly invasive plants especially thrive in disturbed soil. And they self-pollinate, so one large plant can produce 16,000 seeds. Sahara Mustard easily and quickly outcompetes native plants that nourish our wildlife. Without native flora, we lose our native fauna.
As shown below, the plants have rough, hairy leaves that get smaller as they move up the stem. They can be as short as 4 inches or as tall as 40 inches. The flower is tiny, pale yellow, composed of four symmetrical petals.