Vegetable · Brassicaceae
Mustard Greens
Brassica juncea
Get it sown while the weather's still cool, and mustard greens hand over peppery leaves in just a month or so.
Full sun
Every 2–4 days
39–75°F · 4–24°C
30–50 days
Overview
Mustard greens are a fast leafy vegetable in the cabbage family, and they're grown for those peppery, slightly spicy leaves. The plant started out in Asia and now grows all over the world's temperate gardens, just as happy in a Southern row as a Northern raised bed. Give it cool weather and it'll go from seed to plate quicker than pretty much anything else you can put in the ground.
Speed is really the whole point. One sowing can get you a first cutting in 30 to 50 days, and you can pull the outer leaves young while the center keeps cranking out fresh growth. Let a plant fill out and it'll stand about 12 to 18 inches (30 to 45 cm) tall, though plenty of gardeners just crowd them close and harvest a steady patch of tender baby leaves.
The one thing it won't put up with is heat. Warm weather and long days push the plant to throw up a flower stalk, and once it bolts, the leaves turn tough and really bitter. So sow it for the cool ends of the year, keep the soil evenly moist, and the flavor stays bright and clean.
Care
The short version: give it full sun and cool weather, keep the soil evenly moist so the flavor stays mild, work in some rich compost, and harvest quick before summer heat turns the leaves bitter.
Light
Mustard greens like full sun best, but they'll take partial shade without a fuss, which really helps as the season warms up. A bit of afternoon shade in late spring buys you some time before the heat pushes the plants to bolt.
Water
Keep the soil evenly moist and water early so the leaves dry off before nightfall, which keeps fungal disease from taking hold. Don't let the plants dry out and bounce back, though, since that moisture stress turns the flavor unpleasantly sharp and spicy.
Soil
Plant them in rich, well-drained ground with plenty of organic matter worked in. A pH near 6.0 to 6.8 suits them best, though they'll handle soil up toward neutral, and good fertility is what drives all that fast leaf growth you want.
Temperature
This is a cool-season grower, happiest between 39°F and 75°F (4°C to 24°C). It shrugs off a light frost, which can even sweeten the leaves, but warmth up near the top of that range is what gets it bolting.
Humidity
Average humidity, somewhere around 40% to 70%, is all it needs. Airflow matters more than any exact number, since crowded, damp leaves are just asking for the fungal problems that watering early helps you dodge.
Feeding
Work a nitrogen-rich balanced fertilizer into the bed at planting to fuel fast leaf growth. A light nitrogen side-dressing partway through keeps the leaves coming, but easy does it, because too much soft growth pulls in aphids.
Pruning
Cut the outer leaves young and often, and the plant answers back with tender new growth from the center. Once it starts to bolt, pinch out the flower stalk, though by then the leaves have usually gone strong and bitter anyway.
Repotting
Not applicable; direct-sown as a fast garden crop, not container-grown/repotted.
Size & spacing
Plants reach about 12 to 18 inches (30 to 45 cm) tall and roughly the same across. Give full-size plants around 12 inches (30 cm) of room, or sow them thicker and harvest the whole patch as baby leaves.
When to plant
Mustard greens are a cool-season crop, and heat just isn't their thing. Sow the first round in early spring, around three weeks before your last frost, then sow again in late summer for a fall harvest. Cut the leaves young, and try to get the whole crop in before summer warmth pushes it to bolt.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 3-4 weeks before the last spring frost, or direct-sow
- Plant: Early spring (about 3 weeks before last frost) and again in late summer for a fall crop; a cool-season vegetable.
- Harvest: Cut leaves young at about 4-6 weeks; harvest the whole plant before summer heat causes it to bolt.
Hardiness
USDA hardiness zones: 2–11
Temperature: down to -46°C
Troubleshooting
Most mustard-green trouble shows up right on the leaves, so a quick daily look usually catches it early. Match what you're seeing below to the cause, then step in while the planting's still worth saving.
Seedlings flopping over with chewed-up, decayed roots
Seedlings flopping over with no obvious reason? That's often cabbage maggots, little white larvae tunneling through the roots down where you can't see. Pull anything that's already infested and get rid of it so it doesn't spread. Row covers laid down at sowing keep the egg-laying flies away, and skipping the fresh manure means there's nothing drawing them in.
Fix:
- Remove and destroy infested plants
- Protect remaining plants with row covers
Leaves dotted all over with tiny pinholes
See a spray of pinprick holes across the leaves? That's flea beetles, tiny dark things that hop away the second you lean in. The little seedlings get hit hardest, so keep an eye on them. Throw a floating row cover over the bed when you sow, keep the plants growing fast, and a healthy one just shrugs off the light nibbling.
Fix:
- Cover seedlings with floating row cover
- Apply kaolin clay or labeled insecticide if damage is heavy
- Maintain vigorous growth so plants outgrow light feeding
Ragged holes chewed through the leaves
Big torn holes and dark droppings? That's the calling card of cabbageworms and cabbage loopers, green caterpillars that hide against the leaves so well you'll walk right past them. Pick off the ones you can find, and spray Bt if they're really going at it. Honestly, the fix that sticks is netting, which stops the moths from laying eggs at all.
Fix:
- Handpick caterpillars
- Apply Bacillus thuringiensis (Bt)
- Use row covers to exclude egg-laying moths
A stalk rising early while the leaves go harsh
When a stem shoots up the middle and the leaves turn harsh, the plant's bolting, set off by warm weather and longer days. There's no undoing it, so cut those leaves before they go sour on you. Next round, plant in the cool of spring or fall, shade the bed once it heats up, and grab a bolt-resistant type to make life easier.
Fix:
- Harvest promptly before flavor degrades; bolting cannot be reversed
Leaves curling up sticky, with bugs bunched underneath
Crinkled tips and a sticky feel usually mean aphids have moved in on the undersides. Just blast them off with a hard spray of water, and if they come back, insecticidal soap plus a few lady beetles will sort it out. And go easy on the nitrogen, because all that soft, lush growth is exactly the kind of thing aphids can't resist.
Fix:
- Dislodge with a strong spray of water
- Apply insecticidal soap
- Encourage lady beetles and other natural predators
Toxicity
Good news: mustard greens are a food crop and totally safe to have around the house. No part of the plant poisons cats, dogs, or other pets, and the leaves are good to eat besides. The only real thing to flag is livestock grazed heavily on the foliage, where the goitrogens common to all brassicas can build up over time.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
All good here. The ASPCA doesn't list mustard greens as toxic to cats, so if yours grabs a nibble, there's nothing to worry about.
Dogs None
No harm done if a dog crops a leaf. That said, a really big helping of any leafy green can leave the stomach a bit off.
Horses Safe
A horse can graze it in normal amounts without any trouble, since there's nothing toxic in there.
Rabbits Safe
Rabbits do fine with it in moderation. Just ease the leaves in slowly alongside hay and other greens instead of dumping a pile at once.
Livestock Mild
It's good, safe forage, but here's the catch: grazing heavily on the brassica foliage day after day lets the goitrogens build up and lean on the thyroid. So keep it as one part of a mixed diet.
Birds Safe
No problem for birds. Backyard hens love pecking the leaves, and the greens make a nice healthy treat.
People Safe
Great to eat, of course. Those peppery leaves work cooked or raw, and there's no part of the plant you have to skip.
Like other brassicas the foliage contains glucosinolates/goitrogens; this is mainly a dietary concern for livestock grazed heavily on it, not a household-pet poisoning hazard.
Varieties
Mustard greens come in smooth, curled, and red-tinged forms, and a few names keep popping up. Here are the ones worth knowing.
Florida Broadleaf
It's a speedy Southern favorite with big, smooth, broad green leaves you can start snipping while they're still young.
Southern Giant Curled
Its frilled, heavily curled bright green leaves handle a frost better than the flat-leaved ones do.
Giant Red
Grown for looks and bite both, it's got purple red tinged leaves and a good strong peppery kick.
Tendergreen
It's a mild, quick smooth-leaf type folks often grow as a spinach-mustard when they want gentler eating.
How to propagate
Mustard greens grow straight from seed, and you'll be hard-pressed to find a crop that comes up faster or more reliably.
SeedEasy
Direct-sow in early spring and again in late summer for a fall crop · Germinates in about 5-10 days and seedlings establish within roughly 2 weeks
Honestly, it's hard to find an easier seed to grow. Just sow it shallow in cool, moist soil in early spring, then again in late summer for a fall crop, and it'll pop up in 5 to 10 days with the seedlings settled in about two weeks. Want full-size plants? Thin them to roughly 12 inches (30 cm) apart, or leave them close for a nice cut-and-come-again patch.
Myths
A pet that eats mustard greens will be poisoned.
Not so. Brassica juncea is just an everyday edible vegetable, and the ASPCA doesn't list it as toxic to cats or dogs. That goitrogen worry? It's about livestock grazing heavily on the foliage, not a pet grabbing a leaf. For a household with pets, mustard greens are safe.
Mustard greens do their best growing in high summer.
Nope, it's the opposite. This is a cool-season crop that really hits its stride in spring and fall. Summer heat just pushes it to bolt, and once that happens the leaves go harsh and bitter. So sow it for the cool ends of the year instead.