The yellow-flowered mustards that fill Victor Valley lots after the winter rains. How to tell them apart, when to pull them, and why bagging matters.
Get a Free Yard EstimateSahara mustard and London rocket are winter annual weeds that sprout after the High Desert’s December to March rains, flower in late winter and spring with small four-petal yellow flowers, and then dry out into fire fuel. Pull them while they are young, bag them before the seed pods mature, and put down a pre-emergent in late summer to stop next winter’s crop.
Both plants are on the Mojave Desert Land Trust’s list of Mojave invasives (MDLT). Sahara mustard is the more serious of the two. The California Invasive Plant Council rates it High and lists it in both the Mojave and Sonoran Deserts (Cal-IPC). Plenty of people just call either one “mustard weed.”
This page is part of our High Desert weeds guide.
| Sahara mustard | London rocket | |
|---|---|---|
| Scientific name | Brassica tournefortii (Cal-IPC) | Sisymbrium irio (UC IPM) |
| Other names | Saharan, African, Moroccan or Asian mustard (Cal-IPC) | Often lumped in as mustard weed |
| Young plant | Basal rosette of leaves 3 to 12 inches long, a bit like a dandelion (MDLT) | Seedlings have oval, hairless seed leaves on stalks (UC IPM) |
| Mature plant | Rosette with flowering stems | Upright to about 2 feet, lower leaves deeply lobed and up to 6 inches (UC IPM) |
| Flowers | Small, four oblong yellow petals in the shape of an X (MDLT) | Yellow, four petals |
| Seed pods | Form after flowering | Long, thin and straight (UC IPM) |
The quick tell: a big flat rosette of long leaves hugging the ground is the classic Sahara mustard look. Long, thin, straight pods point to London rocket.
Both are winter annuals (Cal-IPC, UC IPM). They sprout after fall and winter rain, flower in late winter and spring, then dry out (MDLT). In the Victor Valley, the rain that starts them is concentrated in winter (NOAA 1991-2020 normals, Victorville):
| Month | Normal rain | What the mustards are doing |
|---|---|---|
| December | 0.94 in | First seedlings after rain |
| January | 0.97 in | Rosettes growing. Pull while small. |
| February | 1.27 in | Wettest month. Fast growth, early flowers. |
| March | 0.78 in | Flowering and setting pods |
| April and May | 0.33 and 0.09 in | Drying out. Seed dropping. |
Sahara mustard gets a head start. UC Riverside’s invasive species center says it germinates and flowers earlier than other mustards, about a month before native plants (UC Riverside CISR). If you wait until you see wildflowers to go pull weeds, the Sahara mustard is already a month ahead of you.
The flowering and drying stages in the table are general timing from MDLT’s description, not exact dates. A wet year pushes everything bigger and later.
Cal-IPC says Sahara mustard can increase fire frequency and fuel load, and can convert desert scrub to grassland (Cal-IPC). A lot full of green mustard in February becomes a lot full of dry, brittle stalks by early summer.
That is also why San Bernardino County’s desert-region rules require weeds and grasses cut to 4 inches or less on lots under five vacant acres (SB County). The rules for each city are on our weed abatement guide.
None of our sources list mowing as the fix for these two. They recommend pulling and bagging. For a lot too big to pull, see the fire-safe clearing notes in our weed abatement guide.
UC IPM’s window for winter annuals is late summer to early fall (UC IPM). In the High Desert, our estimate is late August through September, so the product is in place before the first real fall rain. Victorville’s normal rainfall is 0.31 inches in October, 0.35 in November and 0.94 in December (NOAA).
Water it in. UC IPM calls for about 1/2 inch of water soon after a pre-emergent goes down (UC IPM), and late summer here is dry. Use a product labeled for the weeds and the site, and follow the product label. Many products are not labeled for every plant or site.
The same fall application helps with the other winter weeds too, like red brome. See our foxtails guide for those, and the rock and gravel page for the full pre-emergent timing.
Sahara mustard starts as a flat basal rosette with leaves 3 to 12 inches long, a bit like a dandelion, according to the Mojave Desert Land Trust. It then sends up stems with small yellow flowers that have four oblong petals in the shape of an X.
Sahara mustard and London rocket are winter annuals. They sprout after the December to March rains, which bring most of Victorville’s yearly rain, and flower in late winter and spring. UC Riverside says Sahara mustard germinates and flowers about a month before native plants.
The California Invasive Plant Council rates Sahara mustard High and says it can increase fire frequency and fuel load. The Mojave Desert Land Trust notes that winter weeds like it dry out into fire fuel after spring.
Yes. The Mojave Desert Land Trust recommends bagging pulled plants to reduce the risk of seeds being scattered. Pull them before they set seed if you can.
UC IPM says to apply pre-emergent for winter annual weeds in late summer to early fall. In the High Desert our estimate is late August through September, before fall rain, watered in with about half an inch of water. Follow the product label.
We checked every number on this page against the public sources below. If a rule or date changes, the agency page is the final word.
Bare ground that fills with mustard every winter is ground waiting for a plan. Monarch designs and builds rock, DG and drought-tolerant planting yards across the High Desert. We do not sell weed spraying or lot clearing. Get a free estimate once the ground is clear.
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