Tatsoi, often called Rosette Bok Choy or Spoon Mustard, is a leafy green that grows quickly. This Asian brassica forms a low, thick rosette of dark green, spoon-shaped leaves, offering a mild, slightly sweet flavor with subtle mustard undertones. Its rapid maturity and tolerance for cold temperatures make it a favorite for home gardeners seeking a dependable, cool-weather crop. Tatsoi adds texture and nutrients to salads when young and holds up well in stir-fries, soups, and braised dishes as a mature green.
Essential Growing Conditions
Tatsoi thrives when planted during the cooler parts of the year. The optimal temperature range for robust growth is between 50°F and 75°F (10°C to 24°C), as prolonged heat above 80°F (27°C) will prompt the plant to prematurely flower and set seed, a process known as bolting. While it can handle full sun in cooler climates, providing partial shade is beneficial in warmer regions, helping to moderate soil temperatures and delay bolting.
The plant requires fertile, well-draining soil that is rich in organic matter. Before planting, amend the soil with compost or aged manure to ensure adequate nutrient availability. Tatsoi prefers a slightly acidic to neutral pH, ideally falling within the range of 6.0 to 7.5. Mature plants can withstand light frost and temperatures as low as 15°F (-9°C), allowing the harvest season to extend into winter in many areas.
Sowing and Initial Establishment
Timing the planting correctly is important for a successful tatsoi harvest, with seeds sown either in early spring a few weeks before the last expected frost or in late summer for a fall crop. Direct sowing the seeds into the garden bed is the most common method, as tatsoi generally establishes easily without the need for indoor starting. The tiny seeds should be planted shallowly, barely covering them with about a quarter-inch of fine soil.
Once the seedlings emerge (typically 4 to 12 days depending on soil temperature), they must be thinned to their final spacing to ensure proper air circulation and growth. For harvesting baby leaves, space plants 4 to 6 inches apart for a dense yield. If the goal is to grow large, full rosettes, thin seedlings to a wider spacing of 8 to 12 inches between each plant. The young thinned greens are entirely edible and can be incorporated into a salad.
Cultivation and Maintenance
Consistent moisture is crucial for cultivating tender, flavorful tatsoi, as fluctuating soil moisture can lead to bitter leaves and encourage bolting. Plants require about one inch of water per week, delivered through deep, regular watering to keep the soil evenly moist but never waterlogged. Applying a layer of organic mulch around the plants helps to regulate soil temperature and retain moisture, which is helpful during warm spells.
Since tatsoi is a fast-growing leafy green, its nutritional needs focus on nitrogen. If the soil was well-amended before planting, additional feeding may not be necessary, but a light application of a nitrogen-rich fertilizer can boost leaf production. Managing heat is essential for preventing premature bolting, which diminishes the quality and flavor of the leaves.
Monitor for common brassica pests, including slugs, cabbage worms, and flea beetles, which can quickly damage the leaves. Flea beetles create small, circular holes in the foliage, particularly in the spring, while cabbage worms chew larger, irregular holes. Simple organic controls include handpicking larger pests, applying Bacillus thuringiensis (Bt) for cabbage worms, or covering the crop with a fine mesh row cover.
Harvesting and Usage
Tatsoi is ready for harvest quickly, often yielding baby greens in as little as three weeks from sowing and developing mature rosettes in about 40 to 50 days. There are two primary methods for harvesting. The “cut-and-come-again” method involves snipping the outer leaves individually, leaving the central growing point of the rosette intact. This technique allows the plant to continue producing new leaves for several weeks, extending the harvest window.
Alternatively, the entire head can be harvested at once by cutting the plant about an inch above the soil line. If the weather remains cool, cutting slightly higher can allow the plant to resprout for a smaller second harvest. The entire plant is edible, including the stems, which can be used alongside the leaves. Harvested tatsoi should be washed, dried, and refrigerated quickly to maintain freshness. Succession planting—sowing a small batch of seeds every two to three weeks—ensures a steady supply of fresh leaves throughout the cool season.