How to Grow and Care for Black Mustard

Black mustard herb plant with bright yellow flowers on thin stems against blue sky

The Spruce / Evgeniya Vlasova

In This Article

Black mustard (Brassica nigra)  is one of the oldest and most useful spices and herbs known to humanity. Its young leaves are used as salad greens, its mature leaves are eaten boiled or sauteed, and its seeds are, of course, the source for the tart condiment that bears its name. This beautiful herb native to North Africa and Eurasia is so loved that it has spread worldwide. Both commercial and residential growers have planted it widely, leading to its introduction into local ecosystems.

For those trying to grow black mustard, its blessing is that it is insanely easy to grow and grow in almost any soil condition. The curse is the same: it is insanely easy to grow. It will grow in almost any soil conditions and then spread, and spread some more. It grows so easily that it has naturalized itself almost everywhere it has been introduced and is now considered invasive in some areas. The invasive tendencies are particularly nasty with black mustard because it is allelopathic, making native plants germinate in its vicinity. (Allelopathy is the inhibition of one plant by another, due to the release of chemicals acting as germination or growth inhibitors.)

Black mustard is beautiful, delicious, nutritious, and actually very good for the soil it is planted in if its spread is controlled. Controlling the plant's weedy tendencies is what makes black mustard so troublesome. If you decide you just need to have black mustard in your garden, be prepared to commit to ensuring that you contain any possible spread into the local ecosystem.

Botanical Name Brassica nigra
Common Name Black mustard
Plant Type  Herb, Annual
Mature Size 2 to 8 ft. tall
Sun Exposure Full sun
Soil Type Rich, Moist Loams,
Soil pH Neutral
Bloom Time March to June
Flower Color Bright Yellow
Hardiness Zones USDA zones 4-7
Native Area  North Africa, Eurasia

Black Mustard Care

Black mustard is easy to grow. There is not much that can go wrong when growing it unless you give it too much water or if the plant gets too hot.

When you plant your black mustard, there are so many great uses for the seeds. Be sure to collect them all, and you can avoid spreading this non-native. After all, native plants are better for the environment and our gardens.

Black mustard herb plant with bright yellow flowers on tall thin stems covering field

The Spruce / Evgeniya Vlasova

Black mustard plant stem with small bright yellow flowers on end closeup

The Spruce / Evgeniya Vlasova

Black mustard herb plants with small yellow flowers clustered together in field

The Spruce / Evgeniya Vlasova

Light

Black mustard that grows in meadows and at the edges of tilled land. It needs full sun to grow to perform its best and not tolerate shade well.

Soil

Though it will grow almost anywhere, mustard will do best in moist and loamy but not wet soil. It prefers loose, well-draining soil. The pH range of the soil should fall somewhere between 6 and 7. An easy test of your soil can be taken to determine the pH, and you can watch how your plants are doing. You can always amend your soil to make your plants happy.

Water

There is no real magic number on how much water to give your plant to keep it happy. Consider your weather and keep it consistently moist without letting it sit in standing water, and it will thrive. If your soil is well-draining, you shouldn't be able to drown it.

Temperature and Humidity

Black mustard likes cool air temperatures with moderate humidity and moist soil conditions. If given temperatures that are too warm, black mustard's seeds will ripen much faster and burst, which will lead to you having fields of black mustard in your yard and possibly your neighbor's as well. Black mustard does great in USDA Zones 4-7.

Fertilizer

Depending on the richness of your soil, the addition of fertilizer may not be needed but tilling manure into the soil before planting your mustard is going to give your make your mustard extra peppy and really give it a boost. Growing plants next to your mustard that really taxes the soil for nitrogen like beans and turnips is a great idea since mustard is a phenomenal nitrogen fixer.

Pruning Black Mustard

Again, the issue with black mustard is controlling it from spreading. You do this by responsibly harvesting and managing the plant's seed. Remove the seed pods before they can disperse. You can also manually pull unwanted plants up by hand, ideally prior to the development of any seed pods.