Mustard Greens

Mustard greens (Brassica juncea) are the fastest-returning leafy green you can plant after radish. From direct sowing to first cut, you’re looking at 35 days. The leaves are spicy - more so than arugula, less fire than raw horseradish - and that heat level is what divides gardeners on them. If you cook them, the sharpness mellows dramatically. If you eat them raw, young leaves under an inch are much milder than mature leaves, which is why baby mustard greens end up in spring salad mixes at specialty grocers.

B. juncea is also used as a cover crop and soil biofumigant - the glucosinolates in the plant’s tissue suppress certain soilborne pathogens and nematodes when the green matter is tilled in before it fully decomposes (Punja & Yip, Canadian Journal of Plant Pathology, 2003). This dual-use profile makes mustard greens one of the more practical plants you can put in your rotation.

What you’re actually growing

B. juncea is a distinct species from cabbage, kale, or broccoli (B. oleracea) and from turnip (B. rapa). It’s the source of most commercial mustard seed. The leaves range from flat to deeply crinkled, and color runs from bright green to red-purple depending on variety.

‘Southern Giant Curled’ is the traditional green type - large, crinkled leaves with moderate heat. ‘Red Giant’ has reddish-purple leaves with more pronounced heat and better heat tolerance before bolting than green types. ‘Mizuna’ is technically B. rapa var. nipposinica and a separate species; it’s sometimes grouped with mustard greens culinarily but is a distinct crop (see the mizuna entry). ‘Amara’ is an Ethiopian variety with very strong flavor, grown as both food and biofumigant.

The ROI case

A $1.99 packet of mustard greens seed plants a substantial row. At 3-inch spacing you get 80-100 plants per 25-foot row. Baby greens can be harvested as a cut-and-come-again crop at 35 days; full-size leaves by 45-50 days. USDA AMS Specialty Crop Market News (2023) reports specialty salad greens and mustard greens at $2.00-$4.00/lb at farmers market and specialty retail.

The cut-and-come-again characteristic is the real return mechanism. Cut leaves 1 inch above soil and the plant regrows. A well-managed planting yields 2-3 cuts before bolting, which means roughly 3x the yield per plant compared to a single-harvest crop.

Mustard greens also function as a low-cost cover crop when finished. Till remaining plants into soil 2-3 weeks before planting the next crop. The decomposing tissue suppresses some fungal pathogens.

Growing requirements

Direct sow spring or fall; mustard greens grow best in cool weather (45-75°F) but tolerate light frost and handle early-season heat better than spinach before bolting. In most climates, two windows exist: early spring (sow 4-6 weeks before last frost) and late summer for fall harvest (sow 6-8 weeks before first frost).

Sow 1/4 inch deep, 1 inch apart, in rows 12 inches apart. Thin baby greens by harvesting selectively. For full-size plants, thin to 6 inches.

Soil pH 5.5-7.0. Not particular about soil type as long as drainage is adequate. A basic soil prep with 2 inches of compost is sufficient; mustard greens are not heavy feeders.

Bolting (sending up a flower stalk) is triggered by long days combined with heat. Once the plant bolts, leaves become very hot and tough. In spring plantings, bolt typically occurs in June as days lengthen and temperatures rise. Fall plantings often get 2-3 weeks longer before bolting because day length is decreasing. Red types generally have slightly better bolt tolerance than green types.

What goes wrong

Flea beetles (Phyllotreta species) are the most common problem - small, round holes in young leaves. Row covers prevent access. Heavy infestation on seedlings can kill plants. Diatomaceous earth around seedlings deters adults.

Aphids colonize new growth. Water blast; insecticidal soap for heavier infestations.

Downy mildew (Peronospora parasitica) causes yellow patches on upper leaf surfaces with white fuzzy growth underneath in cool, wet conditions. Improve air circulation, avoid overhead watering, and remove affected leaves. Copper-based fungicides help preventively.

Bolting is the primary productivity constraint - it’s triggered by heat and long days, not a disease or pest. The fix is timing, not treatment. Fall plantings escape much of the bolting pressure.

Harvest and storage

Begin harvesting baby leaves at 35 days, using scissors to cut 1 inch above the soil line. Let the stump regrow for subsequent cuts. For full-size leaves, snap or cut individual leaves from the outside of the plant inward, leaving the growing center intact. Harvest in the morning when leaves are crisp and temperatures are cool.

Fresh mustard greens wilt fast. Use within 3-5 days or store in a damp paper towel in a sealed bag in the refrigerator. For longer preservation, blanch and freeze - cooked mustard greens freeze well. Braised or sauteed mustard greens freeze better than spinach because the leaves are sturdier.

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Related crops: Arugula, Kale

Related reading: Succession Planting Calendar - timing fast-maturing greens for continuous harvest through spring and fall