Komatsuna
A versatile Japanese mustard spinach with glossy, dark green leaves that can be eaten raw or cooked.
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Meet Komatsuna
A versatile Japanese mustard spinach with glossy, dark green leaves that can be eaten raw or cooked. Flavor is mild and slightly sweet compared to other brassica greens, making it a good substitute for spinach in any recipe. Plants are remarkably adaptable, tolerating both heat and cold better than most leafy greens. Harvest at any size from microgreen to full maturity for different culinary applications.
When to plant Komatsuna
Direct sow is preferred as komatsuna establishes quickly and grows fast. Sow one-quarter inch deep in rows from early spring through late fall. Germination takes 3 to 7 days at 50 to 80 degrees Fahrenheit. For earliest spring crops, start indoors 3 to 4 weeks before last frost. Thin seedlings to 4 to 6 inches for full plants or grow closer for baby leaf production.
Your Komatsuna Year
Composed for Zone 7 · typical seasons · frost passes Apr 2, returns Nov 1
Sow Komatsuna Mar – Apr, Aug – Sep, pick May – Jun, Oct – Nov. Set your climate below and every date on this plate re-times itself.
How to grow Komatsuna
Komatsuna, also known as Japanese mustard spinach, is an exceptionally versatile and easy-to-grow Asian green that tolerates both heat and cold better than most leafy vegetables. Direct sow seeds one-quarter inch deep from early spring through late fall, spacing 4 to 6 inches apart in rows 12 inches apart. Seeds germinate quickly in 3 to 7 days at 50 to 80 degrees Fahrenheit.
Komatsuna grows rapidly, reaching harvestable baby leaf size in just 20 to 25 days and full maturity in 35 to 50 days. It tolerates light frost to about 25 degrees Fahrenheit and continues producing in temperatures that cause lettuce to bolt. Provide consistent moisture for the most tender leaves.
Succession sow every 2 to 3 weeks for year-round production. Komatsuna performs well in containers, cold frames, and unheated greenhouses during winter. It is one of the most reliable greens for all-season growing. Apply light nitrogen fertilizer every 2 weeks for lush, rapid growth. Both baby leaves and mature plants are equally delicious.
72 plants fit a 4 × 8 ft bed
Each Komatsuna wants 20 cm of elbow room. The planner keeps that spacing for you — every plant, every bed.
Komatsuna's best neighbours
Komatsuna grows well alongside lettuce, peas, beans, and herbs like cilantro and dill. Radishes make good companions and are ready to harvest before komatsuna needs the space. Avoid planting near other brassicas to reduce shared pest pressure. Marigolds and nasturtiums help deter flea beetles and attract beneficial insects.
Garlic belongs beside it. Strawberry doesn't.
Old growers' knowledge, checked against Komatsuna's real companion table below — test any plant you're growing.
Related growing guides
Feed it well
Komatsuna grows well in any fertile, well-drained soil with a pH between 6.0 and 7.5. Work in compost before sowing for the most productive plants. Apply nitrogen-rich liquid fertilizer every 2 weeks for rapid, tender growth. Komatsuna is not a heavy feeder compared to other brassicas but benefits from consistent nutrition for continuous production.
Ideal Temperature
Hardiness Zone Compatibility
From seed to harvest, stage by stage
Seed Germination
Small round brassica seeds germinate quickly in a wide range of soil temperatures, often emerging within 3-5 days. Rounded cotyledon leaves appear first, pale green and fleshy. Komatsuna seeds are moderately small at roughly 250-300 seeds per gram, making them easy to handle and sow evenly.
Seedling Development
True leaves develop rapidly, showing komatsuna's characteristic broad, rounded shape with smooth edges and a slightly glossy surface. Unlike many mustard greens, komatsuna leaves are thick and succulent from an early stage. The root system establishes quickly in loose, fertile soil.
Rosette Formation
Plants form a compact, upright rosette of thick dark green leaves with pale, juicy stems. Leaves broaden significantly and develop a slight waxy coating that gives them a glossy appearance. This is the phase of maximum vegetative growth and the plant's most productive period.
Mature Harvest Stage
Rosettes reach full size at 25-40 cm tall with thick, succulent stems and broad, dark green leaves. This is the prime harvest window for whole-plant harvest. Outer leaves can be picked individually while the center continues to produce new growth. Flavor is mild and sweet with a gentle mustard undertone.
Bolting and Flowering
As day length increases or temperatures rise, the central stem elongates and produces clusters of small yellow four-petaled flowers. Leaves become tougher and develop a stronger mustard bite. Flower buds and young flower stalks are still edible and have a pleasant mild brassica flavor similar to broccoli rabe.
Seed Set and Completion
Flowers develop into slender seed pods (siliques) that dry and split when mature. Each pod contains 8-15 small round seeds. The plant becomes woody and fibrous as all energy shifts to seed production. Komatsuna freely cross-pollinates with other Brassica rapa varieties, so isolate seed crops if purity matters.
Sow seeds 1 cm deep in moist, well-drained soil. Komatsuna germinates at soil temperatures from 8-30°C (46-86°F), though 15-25°C (59-77°F) is optimal. Keep soil consistently moist but not waterlogged until seedlings are established.
Caring for Komatsuna month by month
What to do each month for your Komatsuna
July
You are hereIn hot climates, pause komatsuna plantings until late August. In maritime or mountain climates with cool summers, continue succession sowings. Irrigate consistently — heat combined with drought stress causes rapid bolting and bitter flavor.
Know exactly what to do in your garden — every month
One email at the start of each month: what to sow, plant, and tackle right now — for your Komatsuna and everything growing around it. Plus a short starter course that helps you dodge the classic mistakes.
- What to do, right now
- Matched to your season
- Starter course included
Harvesting Komatsuna
Harvest komatsuna at any size from baby leaf at 2 to 3 inches to full-grown plants at 10 to 12 inches tall. For baby greens, cut entire plants with scissors just above the soil for regrowth. For mature plants, harvest outer leaves individually or cut the whole rosette. Komatsuna is harvested like a more versatile spinach that does not bolt quickly. Morning harvest ensures maximum crispness.
assuming you sow when the window opens — set your real date
Pick Komatsuna promptly and the plant keeps producing.
Storage & Preservation
Fresh komatsuna stores for up to 1 week in the refrigerator in a sealed bag with a damp paper towel. For freezing, blanch leaves for 1 minute, ice-bath, squeeze out excess water, and freeze in portions. Komatsuna can be pickled Japanese-style with salt and chili. It also works well dried and rehydrated for soups and stews.
What goes wrong — and the fix
Flea Beetles
PestSmall round holes peppering the leaves, most problematic on young seedlings in warm weather.
Slugs
PestIrregular holes in leaves and slimy trails, damage worst in cool damp conditions.
Clubroot
DiseaseWilting in warm weather, stunted growth, and swollen misshapen roots.
Troubleshooting Common Problems
Flea beetles are the most persistent pest, particularly on young seedlings in warm weather. While komatsuna is very bolt-resistant, extreme heat combined with drought can trigger flowering. Clubroot disease affects komatsuna like all brassicas, especially in acidic soil. Overcrowding leads to elongated, lanky plants with reduced leaf quality.
Growing Tips
- Succession sow every 2-3 weeks from early spring through late autumn for an uninterrupted supply. Komatsuna matures in 35-50 days and can produce 5-7 successive crops per year in mild climates, maximizing your harvest from minimal garden space.
- Komatsuna excels as a cut-and-come-again crop — harvest outer leaves when they reach 15-20 cm tall while leaving the growing center intact. A single planting can produce 3-4 harvests over 4-6 weeks using this method, significantly extending the productive life of each sowing.
- Take advantage of komatsuna's exceptional cold tolerance by growing it through winter under simple row cover or in an unheated cold frame. Established plants survive to -6°C (21°F), and frost exposure actually sweetens the flavor as the plant converts starches to sugars for cold protection.
- For baby leaf salad harvests, sow seeds densely at 2-3 cm apart and harvest when leaves are 10-12 cm tall at around 20-25 days. Baby komatsuna leaves are tender, mild, and make an excellent salad green that even children enjoy.
- Komatsuna handles mild summer heat better than most Asian greens, but provide afternoon shade and consistent irrigation when temperatures exceed 27°C (80°F). A shade cloth at 30-40% density over the bed extends the growing season through warmer months.
- Flea beetles are the primary pest — their tiny holes in leaves can devastate young seedlings. Cover newly sown beds with fine insect mesh (0.8mm or smaller) immediately after planting and leave in place until plants are well established with at least 6-8 true leaves.
- Grow komatsuna in containers at least 15-20 cm deep for a productive balcony or patio crop. Its compact rosette habit, shallow roots, and rapid maturity make it ideally suited to container culture. Use quality potting mix and water daily in warm weather.
- Rotate komatsuna with non-brassica crops to prevent the buildup of clubroot (Plasmodiophora brassicae) and other soil-borne diseases. Avoid planting where any brassica — including cabbage, broccoli, bok choy, radish, or turnip — has grown in the previous 2-3 years.
Pick your Komatsuna
Komatsuna
The standard green variety with broad, glossy dark green leaves and mild, sweet flavor.
Red Komatsuna
A striking purple-red variety with attractive coloring that intensifies in cool weather.
Tendergreen
A hybrid selection with extra-tender leaves and excellent bolt resistance for warm-season growing.
Senposai
A komatsuna-cabbage cross with large, tender leaves and very mild flavor.
Komatsuna offers excellent value for home growers. A single seed packet ($2-4) contains 200-500+ seeds — enough for an entire season of succession plantings. Fresh komatsuna sells for $4-7 per bunch at Asian grocery stores and $6-10 per pound at specialty farmers markets, and organic komatsuna commands even higher prices. A modest 3-meter garden bed with successive sowings can yield 6-12 kg over the season, representing $60-150 in savings compared to retail prices. Because komatsuna matures in just 35-50 days, offers multiple harvests per planting, and grows nearly year-round in mild climates, it delivers one of the highest returns on garden investment per square meter of any leafy green.
Quick recipes
Sesame Garlic Komatsuna Stir-Fry
10 minA quick and aromatic stir-fry that highlights komatsuna's juicy stems and mild mustard flavor. The high heat of the wok keeps the leaves vibrant and the stems crisp-tender, while toasted sesame oil and garlic create a fragrant, savory finish.
8 ingredientsKomatsuna Miso Soup
15 minA comforting Japanese home-style miso soup featuring tender komatsuna leaves, silken tofu, and a rich dashi broth. Komatsuna holds up beautifully in hot broth without becoming slimy, making it the preferred green for miso soup throughout Japan.
6 ingredientsJapanese Komatsuna Ohitashi
8 minA classic Japanese side dish of blanched komatsuna dressed in a savory dashi and soy sauce mixture, served chilled. This elegant preparation showcases the clean, mild flavor and satisfying texture of komatsuna at its simplest and most refined.
6 ingredientsCulinary Uses
Komatsuna is incredibly versatile, suitable for raw salads, stir-frying, steaming, braising, and soup. The mild, slightly sweet flavor works in both Asian and Western dishes. It is a staple in Japanese home cooking, often sauteed with sesame oil and soy sauce. Use as a spinach substitute in any recipe. Baby leaves are excellent in salad mixes.
What's inside
Health Benefits
- Outstanding source of vitamin C (130mg per 100g, 144% DV), providing potent antioxidant protection that supports immune function, enhances iron absorption from plant foods, and is essential for collagen synthesis in skin, joints, and connective tissues.
- Exceptionally high in bioavailable calcium (210mg per 100g) with very low oxalate levels — unlike spinach, the calcium in komatsuna is readily absorbed by the body, making it one of the best plant-based sources for supporting bone density, muscle contraction, and nerve signaling.
- Rich in beta-carotene and vitamin A (63% DV per 100g), critical for maintaining healthy vision, supporting skin cell turnover, and bolstering immune defenses — particularly the mucosal barriers in the respiratory and digestive tracts.
- Abundant in vitamin K (over 170% DV per 100g), which plays an essential role in blood clotting, bone metabolism, and emerging research suggests cardiovascular health through its regulation of calcium deposition in arteries.
- Contains glucosinolates and isothiocyanates — sulfur-containing compounds characteristic of brassica vegetables that have been extensively studied for their anti-inflammatory and potential anti-cancer properties, particularly in supporting the body's detoxification enzyme systems.
- Provides significant iron (2.8mg per 100g) alongside its extremely high vitamin C content, creating an ideal pairing for non-heme iron absorption. This combination makes komatsuna particularly valuable for vegetarians, vegans, and anyone managing iron levels through diet.
Where Komatsuna comes from
Komatsuna (Brassica rapa var. perviridis) originated in Japan, where it was developed from Chinese mustard greens and turnip relatives brought to the archipelago centuries earlier. The vegetable's name traces directly to the Komatsugawa district of Edo (present-day Tokyo), where it was first cultivated as a distinct variety during the early Edo period in the 17th century. A well-known legend credits Shogun Tokugawa Yoshimune with naming the green after enjoying it during a hunting excursion near Komatsugawa around 1719.
Over the following centuries, komatsuna was refined through selective breeding by Japanese farmers who prized it for its mild flavor, thick succulent stems, rapid growth, and exceptional cold tolerance. Unlike many brassicas that were bred for a single harvest, komatsuna was developed as a cut-and-come-again crop suited to the small, intensively managed plots typical of Japanese agriculture. Regional varieties proliferated across Japan, each adapted to local climate conditions — from snow-hardy types in Hokkaido to heat-tolerant strains in Kyushu.
By the 20th century, komatsuna had become the most consumed leafy green in Japan, outpacing even spinach in household consumption. Its low oxalate content, high calcium, and versatility in the kitchen made it a nutritional cornerstone of the Japanese diet. In the postwar era, improved varieties were developed for year-round greenhouse and open-field production, and komatsuna became a staple of Japanese school lunch programs nationwide. Today, komatsuna is gaining international recognition among gardeners and chefs worldwide, valued for its ease of cultivation, exceptional cold hardiness, nutrient density, and gentle flavor that appeals to those who find other mustard greens too pungent.
Komatsuna: did you know?
Fascinating facts about Komatsuna
Komatsuna (Brassica rapa var. perviridis) gets its name from Komatsugawa, a district in Edo (now Tokyo), where it was first cultivated in the early Edo period around the 17th century. Legend holds that the Tokugawa Shogun Yoshimune named it after tasting the green during a falconry hunt near Komatsugawa.
Komatsuna questions, answered
When should I plant Komatsuna?
What are good companion plants for Komatsuna?
What hardiness zones can Komatsuna grow in?
How much sun does Komatsuna need?
How far apart should I space Komatsuna?
What pests and diseases affect Komatsuna?
How do I store Komatsuna after harvest?
What are the best Komatsuna varieties to grow?
What soil does Komatsuna need?
What does komatsuna taste like?
Can komatsuna replace spinach in recipes?
How cold-hardy is komatsuna compared to other greens?
Why is my komatsuna getting small holes in the leaves?
How is komatsuna different from tatsoi?
When is the best time to harvest komatsuna?
You just read the theory. Now grow it on autopilot.
Everything that makes Komatsuna fiddly — the timing, the spacing, the companions, the harvest window — is exactly what PlotMyGarden handles for you, for every plant in your garden.
A plan that knows your weather
Set your location once. Get sow, feed and harvest dates built around your real last-frost date and live forecast — no more guessing from a generic seed packet.
From the “When to plant” sectionDrag-and-drop bed planner
Design beds on a grid. Every plant snaps to its proper spacing, and you can see your whole season laid out before you spend a cent on seed.
From the “Growing guide” sectionCompanion conflicts, caught early
200+ good-and-bad pairings checked live as you plant — so a season-wrecking mistake never makes it into the ground.
From the “Companions” sectionReminders you'll actually act on
“Water the beans.” “Pick today before it turns.” Timely, specific, and tied to the plants you're really growing.
From the “Harvest” sectionSuccession, scheduled
Want a harvest for six weeks, not six days? It spaces your sowings automatically and reminds you when each new block is due.
From the “When to plant” sectionA record that gets smarter
Every harvest you log teaches it your garden. Next year's plan starts from what actually worked in your soil, not a textbook's.
From the “Overview” sectionPlant these alongside Komatsuna
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