Vegetable · Brassicaceae
Mustard Greens
Brassica juncea
Sown while the air stays cool, mustard greens unfurl broad, peppery green blades in hardly a month.
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, grown for their peppery, slightly spicy leaves. Each plant forms a loose rosette of broad green blades that stand up from a short base, some smooth and flat, others ruffled and crimped along the edge depending on the type. Native to Asia, it now grows across temperate gardens worldwide and moves from seed to plate faster than almost anything else in cool weather.
Its speed is the striking thing. A single sowing reaches a first cutting in 30 to 50 days, and pulling the outer blades young leaves the center to keep unfurling fresh, tender leaves. Grown out, a plant stands about 12 to 18 inches (30 to 45 cm) tall in a spreading clump of foliage, though close sowing yields a low, dense mat of baby leaves instead.
Heat undoes that leafy form. When warm weather and long days arrive, a slim flower stalk pushes up through the center of the rosette, and once the plant bolts the blades stiffen and their flavor turns sharply bitter. Sown for the cool ends of the year and kept in evenly moist soil, the leaves stay broad, tender, and clean-tasting.
Care
The short version: full sun and cool weather, soil kept evenly moist so the flavor stays mild, rich ground worked with compost, and a prompt harvest before summer heat turns the leaves bitter.
Light
Mustard greens grow broadest and greenest in full sun, but they take partial shade without complaint, which helps as the season warms. A little afternoon shade in late spring holds off the heat that drives up the flower stalk.
Water
Keep the soil evenly moist and water early so the leaf blades dry before nightfall, which holds fungal disease at bay. Let the plants dry out and rebound and that moisture stress sharpens the leaves to an unpleasant, spicy bite.
Soil
Plant in rich, well-drained ground worked with plenty of organic matter. A pH near 6.0 to 6.8 suits them best, though they handle soil up toward neutral, and good fertility fills out the broad, fast-growing leaves.
Temperature
This cool-season grower is happiest between 39°F and 75°F (4°C to 24°C). A light frost does no harm and can even sweeten the blades, but warmth at the top of that range pushes up the bolting stalk.
Humidity
Average humidity around 40% to 70% is all it asks. Airflow counts for more than any exact number, since crowded, damp leaves invite the fungal spotting that watering early is meant to avoid.
Feeding
Work a nitrogen-rich balanced fertilizer into the bed at planting to fill out the leaves fast. A light nitrogen side-dressing partway through keeps new blades coming, though too much soft growth draws aphids to the tender tips.
Pruning
Cut the outer leaves young and often, and the plant answers with tender new blades unfurling from the center. Once the flower stalk rises, pinch it out, though by then the leaves have usually stiffened and turned bitter.
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 as wide, a spreading clump of foliage. Give full-size plants around 12 inches (30 cm) of room, or sow thicker for a low mat of baby leaves.
When to plant
Mustard greens are a cool-season crop with no tolerance for heat. The first sowing goes in early spring, about three weeks before the last frost, and a second follows in late summer for a fall crop. The leaves come off young, and the whole plant is cut before summer warmth drives up the flower stalk.
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 reads right off the leaf surface, so a close daily look at the blades catches it early. Match what you see below to its cause, then act while the planting is still worth saving.
Limp seedlings atop roots riddled with tunnels and rot
A seedling that looked sound the day before goes limp and folds flat to the soil, and lifting it shows roots riddled with tunnels and soft with rot. Cabbage maggots, pale white larvae, have bored through the root zone below ground. A collapsed plant will not recover and is best pulled and cleared; row covers set at sowing bar the egg-laying flies, and fresh manure only draws them near.
Fix:
- Remove and destroy infested plants
- Protect remaining plants with row covers
Needle-fine pits stippling the leaf blades
The leaf blade shows a fine stipple of round pinprick holes, each no wider than a needle, and the wounds cluster thickest on the softest young seedlings. Behind them are flea beetles, tiny dark specks that spring off the surface the moment a hand nears. A floating row cover laid at sowing shuts them out, and a plant thickening fast fills in faster than they can chew.
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
The blades come away torn and ragged, chewed clear through and dotted with dark grains of frass. The culprits are cabbageworms and cabbage loopers, plump green caterpillars whose color melts into the green leaf so they hide in plain sight. Fingertips pick off the ones you spot, a Bt spray clears a heavier feeding, and fine netting keeps the parent moths from laying eggs at all.
Fix:
- Handpick caterpillars
- Apply Bacillus thuringiensis (Bt)
- Use row covers to exclude egg-laying moths
A slim stalk climbing from the rosette as blades toughen
A slim central stem shoots up from the leafy rosette and stiffens, and the once-tender blades toughen while the flavor sharpens to a bitter edge. This is bolting, set off by warm weather and lengthening days, and it will not turn back. The leaves are best cut before they sour; a cool spring or fall planting, afternoon shade, and bolt-resistant types hold the stalk down longer.
Fix:
- Harvest promptly before flavor degrades; bolting cannot be reversed
Inward-curling blades glazed sticky and dotted with insects
The youngest leaf tips pucker and curl inward, glazed with a tacky film that catches the light, and turning a leaf reveals green clusters packed along the veins. These are aphids feeding on the underside. A hard jet of water knocks them loose, insecticidal soap wipes out the holdouts, and lady beetles patrol the rest; soft, sappy growth from heavy nitrogen is what they crowd onto.
Fix:
- Dislodge with a strong spray of water
- Apply insecticidal soap
- Encourage lady beetles and other natural predators
Toxicity
Mustard greens are a food crop and safe to keep around the house. No part of the plant, from the broad green leaf to the root, poisons cats, dogs, or other pets, and the leaves are good to eat. The one note is for 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
Safe for cats. The ASPCA leaves mustard greens off its list of plants toxic to cats, so a bite taken from the leafy blade does no harm.
Dogs None
Safe for dogs. A dog that tears off a leaf comes to no harm, though a big mouthful of any leafy green can leave the stomach briefly unsettled.
Horses Safe
Safe for a horse to graze in normal amounts, with no toxic compounds in the green foliage that would put it at risk.
Rabbits Safe
Safe for rabbits in moderation. They crop the tender leaves readily, so work them in gradually beside hay and other greens rather than all at once.
Livestock Mild
Sound, safe forage, but heavy day-after-day grazing on the broad brassica foliage lets goitrogens accumulate and press on the thyroid. It is best kept as one part of a varied diet.
Birds Safe
Safe for birds. Backyard hens shred and peck at the leaves, taking the greens as a healthy treat.
People Safe
Safe and good to eat. The peppery green leaves go into the kitchen cooked or raw, with no part of the plant off limits.
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 the differences show plainly in the leaf. These are the ones worth knowing.
Florida Broadleaf
A fast Southern favorite whose large, smooth, broad green leaves lie flat and wide and can be cut while still young.
Southern Giant Curled
Its bright green leaves ruffle and crimp along frilled, heavily curled edges, and they take a frost better than the flat-leaved kinds.
Giant Red
Purple red tints wash across its leaves over a green base, and that color pairs with a strong peppery flavor.
Tendergreen
A mild, quick type with smooth, unruffled leaves, often grown as a spinach-mustard for gentler eating.
How to propagate
Mustard greens are grown straight from seed, and few crops break the surface 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
The seed is tiny and round, and it comes up quick. Sown shallow into cool, moist soil in early spring, and again in late summer for a fall crop, the first pale seed leaves break the surface in 5 to 10 days, with seedlings settled in about two weeks. Thin them to roughly 12 inches (30 cm) apart for full, broad-leaved plants, or leave them close for a dense cut-and-come-again patch.
Myths
The leaves of mustard greens poison cats and dogs.
Brassica juncea is an everyday edible vegetable, and the ASPCA does not list it as toxic to cats or dogs. The goitrogen worry belongs to livestock grazed heavily on the foliage, not a pet that nibbles a leaf. For a household with pets, mustard greens are safe.
Mustard greens put on their best leaves in summer heat.
This is a cool-season crop that does its best work in spring and fall. Summer heat pushes it to bolt, and the leaves toughen and turn bitter once it does. The cool ends of the year are when it grows sweetest.