Tatsoi

Main crop: direct-seed for fall and winter cutting

Direct-seed tatsoi a quarter to a half inch deep in late summer to early fall, timing sowings so the stand matures as temperatures fall, and repeat every couple of weeks for a continuous supply. Sow thickly rather than in careful stations, then thin as you cut - the crowded stand smothers weeds and the thinnings are salad. Cut leaves about an inch above the ground for cut-and-come-again. Expect baby leaf in roughly three to four weeks and full 8-inch rosettes in six to seven, depending on variety and how cold it is running. Tatsoi is a cool-season brassica that builds its sweet, tight rosette in falling temperatures, and fall sowings run into cold as they mature, which is the direction that suppresses bolting. It is normally direct-seeded: brassica greens establish easily from seed, and transplant stress is itself one of the triggers that sends the plant to seed.

Spring sowing: get it in and out before heat

You can sow a spring crop as soon as the soil can be worked, but plan to cut it at baby-leaf size rather than waiting for full rosettes. Do not rush seed into cold soil to gain a week, and do not let a spring stand sit once warm weather arrives. Asian brassica greens bolt in response to cold temperatures in spring as well as to transplant stress - a seedling chilled early reads it as a completed winter and runs to seed. Spring plantings then finish into rising heat, which pushes the same result, so the spring window is genuinely narrower than the fall one.

Band nitrogen at seeding, and do not overdo it

Work fertilizer into a band near the seed row at sowing rather than broadcasting it wide. Leafy greens as a class want the equivalent of 75 to 150 pounds of nitrogen per acre over the crop, with soil pH held at 6.5 to 7.5. Cut the rate back if the bed got manure or compost, or if it follows a legume cover crop. Tatsoi has a shallow root system living mostly in the top foot of soil, so it responds to banded fertilizer it can actually reach and wastes broadcast nitrogen. Excess nitrogen is not free yield either - it produces soft, watery growth that invites aphids and tipburn.

Flea beetles: check young plants, treat at one beetle per plant

Walk the bed and look at seedlings for shot-hole feeding. On young plants, treat when you average about one beetle per plant or roughly 10 percent leaf damage. If you need a material, spinosad (sold as Entrust in the organic formulation) gave the best control in UMass trials; kaolin clay (Surround WP) is the non-toxic alternative but needs constant agitation to stay in suspension. Tatsoi is susceptible from emergence right through to harvest, not just at one stage, and because you eat the leaf there is no cosmetic slack. Seedlings are where the damage compounds - beetle feeding that stunts a cotyledon costs you the whole plant, while the same beetles on an established rosette cost you a few holes.

⚠ Follow the label's days-to-harvest interval; systemic insecticides carry noticeably longer intervals than contact products, and tatsoi is often cut within days of a spray, so time the application to the next cutting and not to your convenience. Do not spray any insecticide on a stand that has bolted into flower - bees work brassica bloom hard.

Cabbageworms and diamondback moth: Bt while the caterpillars are small

Scout for green larvae, frass and chewed leaves, and spray Bacillus thuringiensis while the caterpillars are still small. Bt is the right call when diamondback moth is the species you are finding, or when any of them are caught young. Spinosad works on larger larvae that Bt will no longer touch, but it is less selective. Bt has to be eaten to work and it kills small larvae far more reliably than large ones, so a late spray simply fails - the pesticides are less effective once the caterpillars have size on them. Bt also spares the parasitoid wasps and predators that carry the rest of your season, which a broad-spectrum material would remove along with the pest.

⚠ Always follow the label and observe the stated number of days between application and harvest. Never spray an insecticide on plants in flower.

Row cover over the bed the day you seed it

Lay spun-bonded row cover or insect mesh over the bed immediately after seeding, and secure every edge with soil or sandbags - a gap anywhere is an open door. If you need to cultivate, pull the cover and put it back the same day. Also site this planting as far as you can from where you grew brassicas last season. Tatsoi has glossy, unwaxed leaves, which puts it in the group of brassicas flea beetles find most attractive, and unlike a cabbage the whole damaged leaf is the product you are selling or eating. Flea beetles overwinter in and near last year's brassica ground, so distance plus an intact barrier beats spraying them after they arrive.

Row cover on hoops for winter standing

For winter harvest, hold tatsoi under a medium-weight row cover supported on hoops rather than laid on the leaves. Under an unheated tunnel this combination carries tatsoi through the dead of winter. Add a second layer if you are trying to keep the greens from freezing outright on the coldest nights. Tatsoi is one of the short list of greens - with spinach, mache, claytonia and minutina - that actually survives the dead of winter under cover rather than merely finishing a fall crop. A medium-weight cover on hoops buys 5 to 10 degrees F, and more on the coldest nights, which is the margin that decides whether the crown lives.

Cut only after the leaves have thawed

Harvest with a sharp knife, cutting the rosette about an inch above the ground so it regrows, or take outer leaves and leave the center. In cold weather, wait for the plants to thaw before you cut - after a hard night that often means mid-morning. Frozen tatsoi leaves are brittle and rupture when cut or handled, so the cells collapse as they thaw and the harvest turns to slime in the box. Frost itself is not the problem - tatsoi sweetens under it - the problem is only cutting the tissue while it is still frozen.