Mustard greens are a staple in grocery stores and the seeds are used to make one of the most popular condiments in the world, yet they are seriously underrated in the garden.
They are low maintenance, resilient green vegetables that provide a kick to dishes that few other vegetables can. Even if you have no space, plant some in the corner of your garden and you won’t regret it.
If you already have experience growing other leafy greens like kale, you can follow the same approach with mustard greens. However, mustard greens need less fertilizer to live and can have different spacing requirements. Mustard also does better when the soil is well-draining and doesn’t stay too wet. Plant mustard greens early in the year for a spring/summer harvest or plant in mid to late summer for a fall harvest.
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Space Requirements for Mustard Greens
How much space you give your mustard greens depends on how large you want your mustard leaves to get. If you want large, full-sized mustard greens for steaming, boiling, or sautéing, plant them anywhere from 12 to 16 inches apart, depending on the variety.
If you don’t mind smaller mustard leaves, which are still great for cooking but can also add a kick to salads, you can plant them much closer. According to the square-foot garden method, you can plant up to 16 mustard plants within one square foot.
Growing Mustard Greens in Containers
For full-sized mustard greens, plant them in 1 1/2 to 2-gallon containers, while smaller mustard greens can be grown in 1/2 to 1-gallon pots. Again, you can apply square-foot gardening principles to a container as well.
I have grown four mustard plants in one container not much larger than 1 gallon. The leaves rarely grew larger than 4 inches long, but the plants were still healthy.
When and How to Plant Mustard Greens
You can direct sow outside or start your mustard greens indoors. Since mustard is frost tolerant, you can plant well before your last frost as long as the tender seedlings are protected. Mustard greens grow very quickly once the weather warms up, and you can start harvesting within 40 days for some varieties.
Direct sow: For an early harvest, sow seeds under cover a few weeks before your last frost date, or whenever the ground is workable. Germination is slow when cold, but it will give you a head start on the season. You can also plant after the last frost without protection. Plant a few seeds in each hole, about 1/8 to 1/4 inch deep, and thin out after they sprout.
Transplant: Start seeds indoors under grow lights at least two weeks before your last frost, then transplant outside.
Planting for a fall harvest: Since mustard tends to bolt (produce a flower stalk) in the height of summer, you can plant a fall crop of mustard 6 to 8 weeks before your average first frost date. Mustard is frost hardy and will continue to give you harvests well after a killing frost takes your your tomatoes and peppers.
Taking Care of Your Mustard Greens
Light and Water Requirements for Mustard Greens
Mustard greens thrive in lightly moist, well-draining soil or potting mix. Don’t let your mustard greens dry out, but at the same time, don’t keep them in standing water. When plants are mature, give them a deep watering when the top 1 1/2 inches or so of soil is dry. When your mustard seedlings are still small, water more frequently.
Mustard is similar to other leafy greens in that it grows best in full sun, but also tolerates partial shade. If mustard grows in very hot and dry conditions, it’s prone to bolting, which makes the leaves spicier to eat.
Fertilizing Mustard Greens
Like most leafy green vegetables, mustard is not a heavy feeder but does need more nitrogen than other vegetables.
For regular feedings, apply a dilute liquid fertilizer every 7 to 14 days (or as per the instructions) after your mustard greens start growing. Any all-purpose fertilizer will suffice, but one with more nitrogen (higher N in the NPK value) is optimal, such as MiracleGro’s all-purpose feed.
Some recommend fertilizing throughout the growing season while others prefer to give mustard all the fertilizer it needs early in the season.
For organic options, liquid fish emulsion, seaweed fertilizer, or compost tea are all highly effective fertilizers.
If you decide to use a slow-release fertilizer once early in the season, any all-purpose slow-release fertilizer will work. Organic slow-release fertilizers good for mustard include blood meal, alfalfa meal, and worm castings. If you have a very long growing season or your soil is poor, you can top dress with more slow-release fertilizer every 1 to 2 months.
How to Harvest Mustard Greens
Harvest the leaves regularly using the cut-and-come-again method. This method involves picking off the lower, larger leaves first while leaving a few leaves at the top of the plant for photosynthesis. This allows the plant to continue growing quickly, allowing more frequent harvests.
If you don’t harvest regularly, you will notice some of the lower leaves turning yellow and falling off, which is a natural process as the mustard plant grows.
Mustard greens are ready to eat at any stage of growth, whether you’re picking baby greens or large curly leaves for steaming. You can also grow and harvest mustard as spicy microgreens.
If your mustard plant starts to bolt, you can still harvest the leaves, but they will be spicier, similar to how arugula leaves become spicier after bolting. The buds, flowers, and of course the seeds, are all edible as well.
Common Mustard Green Problems
Mustard is a very hardy vegetable and doesn’t easily succumb to pest pressure.
Although it’s in the Brassica family (kale, cabbage, broccoli, etc.) it’s not as attractive to cabbage worms and loopers, so expect small white butterflies to prefer your kale instead of mustard.
In young plants, you may notice tiny holes in leaves – this is likely due to flea beetles. Flea beetles are tiny beetles, very shiny in appearance, that quickly jump when disturbed. They are mainly a threat to young plants but naturally become less of a problem as the plants get larger and more mature.
The easiest way to control mustard pests is to use insect netting or row covers early on in the season and check your plants regularly. If you already have an infestation of cabbage worms, flea beetles, you can apply diatomaceous earth or neem oil, both of which are all-purpose organic options.
Other organic pesticides include Bt, which is a bacterium that specifically infects insects, insecticidal soap, and pyrethrin, which is a natural pesticide made from a type of chrysanthemum flower and breaks down rapidly in the sun.
Mustard is also relatively resistant to disease, but if grown in very wet, humid conditions, several fungal and bacterial diseases can take root.
The most common disease you will see as a gardener is damping off, which affects seedlings. If your mustard seedlings are growing in very wet conditions, you may notice some of your plants flopping over or just dying shortly after germination. The best way to combat damping off is to make sure you don’t overwater your seedlings, which is a high risk factor for damping off.
Mature plants can also get infected with clerotinia stem rot, which kills the mustard plant at the stem level, and clubroot, which is a parasitic plant infection that infects the roots of mustard, leading to leaf drop, slower growth, and wilting. Both diseases are very hard to control, but they prefer warm, moist conditions, so controlling these factors can prevent future outbreaks. Clubroot also thrives in acidic soil.
Mustard Plant Varieties
- Southern Giant Curled – My personal favorite, this is a classic, large, curly-leafed mustard with a relatively mild taste. It’s relatively slow to bolt and grows well in the South.
- Japanese Giant Red – A purple-leaf mustard with green stems and a very strong, mustardy taste. Great for cooking, pickling, or eating fresh as baby greens.
- Green Wave – Another green, curly-leafed mustard that is compact (growing to about 2 feet) and has impressive yields. It also doesn’t bolt quickly and can survive cold temperatures more easily.
- Osaka Purple – A milder version of the Japanese Giant Red, this mustard has rich flavor and can be harvested as baby greens in as little as 20 days.
- Mizuna – A mustard green with serrated, feather-shaped leaves, mild flavor, and very prolific while generally growing no more than a foot tall. Excellent for small containers.
- Tendergreen – Smooth, rounded leaves and a very, very mild flavor. Can be used as a spinach substitute in a pinch. Resistant to high temperatures and drought.