Mizuna

Sow seed into moist soil a quarter to a half inch deep once the soil can be worked, in a bed with a pH near 6.0 to 6.5 and at least six hours of sun. Mizuna is best seeded straight into the ground rather than started indoors, and it germinates from 55 to 75F and will still come up in soil as cold as 40F. Seed buried deeper than half an inch usually never emerges, and mizuna is a cool-season green that sizes up best before summer heat pushes it to bolt.

Look over the seedlings at least twice weekly, hunting for shallow pits and rounded shot holes under an eighth of an inch. Keep it up until plants carry four to five true leaves, then ease off. Treat seedlings if you find roughly one to five beetles per plant. Flea beetle injury is severe on young plants and shrugged off later, so the entire decision window is the few weeks between emergence and the fourth or fifth true leaf.

If scouting finds about one beetle per plant or ten percent leaf damage on young plants and cover was not an option, spray spinosad, which had the greatest efficacy of the organic materials in trials. Kaolin clay and pyrethrin are weaker alternatives. Spray only while plants are seedlings, then stop. Only the adult beetle chewing seedling leaves is worth a spray, since a plant past four or five true leaves outgrows the feeding and the crop is a leaf you eat raw.

Lay floating row cover or insect netting immediately after seeding and bury or weight every edge so nothing can walk under it. Put the bed somewhere you did not grow brassicas last fall. Crucifer and striped flea beetles overwinter as adults in shrubby borders and emerge in May hunting exactly this crop, and mizuna is one of the tender non-waxy greens they prefer over cabbage or kale. Cover is only a barrier if it goes on before they arrive and the ground underneath is not already holding them.

Harvest in the morning once the dew has dried but before the heat softens the leaves. For repeat cuts, shear the greens two inches or more above the ground and leave the crown; to end the crop, cut the whole plant off near the soil. The growing point sits low in the rosette, so a cut above it leaves the plant intact to push a fresh flush, and leaves picked cool and dry hold their texture instead of wilting.

Look up your own average first frost date and count back roughly 30 to 40 days to set your sowing date, then keep sowing a small patch every few weeks for a steady supply of young leaves. Mizuna and its mustard relatives mature in about a month and survive light frost, so a crop timed off your local frost date rides the cooling weather instead of fighting summer heat.

After you take a cutting, side dress lightly with a nitrogen source alongside the row and water it in. Cutting the crop removes most of the leaf the plant built, and a light shot of nitrogen after cropping is what pushes it to develop new leaves for the next harvest.

For a late crop under a tunnel or cold frame, keep row cover on hand and pull it over the greens whenever the forecast drops below 25F. Harvest by cutting an inch or two above the soil and the rosette will regrow, faster in warm spells and slowly in cold ones. Mizuna keeps producing well past frost under protection, and 25F is the point where the crop needs a cover over it rather than the tunnel alone.