Mustard Greens

Sow the spring crop as early as the soil can be worked

Direct seed a quarter to a half inch deep once the soil has thawed and drains, and thin the seedlings to four to eight inches apart, in rows twelve to sixteen inches apart. Seed emerges in three to seven days, and germination stalls below 40F, so there is no gain in sowing into ground that is still cold. Mustard is a cool-season green that bolts once heat arrives, so every week of cool weather you give it early is a week of tender leaves before the plant runs to seed.

Sow the fall crop once the worst heat breaks

Direct seed a quarter to a half inch deep in late summer, timing it so plants size up as the weather cools rather than germinating into peak heat. Thin to four to eight inches apart in rows twelve to sixteen inches apart. Germination stagnates above 85F, and the fall crop is the better one anyway: it grows into cooling weather instead of racing the heat, so it never gets the bolting signal that ruins the spring planting.

Light nitrogen side dressing after each cutting

After you crop the plants, side dress lightly with nitrogen alongside the row and water it in. Adjust the rest of the fertility before planting based on a soil test, and hold the soil pH between 6.0 and 6.5. You are harvesting the leaves themselves, so every cutting removes the nitrogen the plant needs to build the next flush of them; without it the regrowth comes back thin and slow.

Scout leaf undersides for young caterpillars

Check the undersides of leaves weekly for cabbage looper, imported cabbageworm, and diamondback moth larvae and their frass. Handpicking is genuinely effective in a garden-sized planting. Act while the caterpillars are still small rather than waiting until the damage is obvious. Insecticides, including the organic ones, are far more effective against small young caterpillars than large ones, so the scouting is what makes any later spray work at all.

Bacillus thuringiensis for caterpillars, while they are small

When scouting turns up young loopers, cabbageworms, or diamondback larvae, spray Bacillus thuringiensis var. kurstaki and cover the leaf undersides where the caterpillars actually feed. Bt is short-lived on the leaf, so repeat while pressure lasts. If Bt is not holding, spinosad also works on brassica caterpillars. Bt kurstaki is a stomach poison that has to be eaten to work, and only young larvae ingest enough to die, which is why a late spray on big caterpillars fails while an early one succeeds.

⚠ Bt kurstaki carries a zero-day preharvest interval on greens and spinosad a one-day interval on mustard, so check your label before picking. Do not spray plants you have let bolt into flower, since bees work mustard bloom, and spinosad is toxic to bees while the spray is still wet.

Cover seedlings against flea beetles

Lay floating row cover over the bed right after sowing or transplanting, on hoops or straight on the plants, and bury or weight the edges on all sides so beetles cannot walk underneath. Treat when you find one to five beetles per plant or defoliation reaches 10 to 30 percent. If you are letting a few plants bloom for pollinators, pull the cover off those before the flowers open. Flea beetles chew small round holes straight through the leaves you intend to eat, and they hit hardest at the seedling stage in spring, when a plant has too little leaf area to outgrow the damage.

Let the frost land, but cover for a hard freeze

Leave the fall planting out through ordinary frosts, which it takes without harm. When a hard freeze is forecast, throw row cover or a blanket over the bed and pick anything you want at full quality first. Fall mustard tolerates frost, and the cold is part of why the fall crop eats better, but a hard freeze is a different event and will damage the plants outright.

Cut and come again, starting at baby leaf

Pick fully expanded outer leaves and leave the crown standing, or cut the whole plant just above the crown and let it push a second flush. Mustards reach full maturity anywhere from 25 to 50 days from sowing depending on the cultivar, and you can start taking leaves as baby greens well before that. Skip yellowing or dead leaves. Mustard regrows from the crown, so taking the outer leaves rather than the whole plant turns one sowing into several harvests, and picking young keeps the leaves before the pungency and toughness climb.