Asian Greens / Mustards · Cool-season annual leafy vegetable; open-pollinated

Ruby Streaks Mustard New · Sep 2026

Brassica juncea 'Ruby Streaks'· Ruby Streaks mustard, Red mustard, Purple mizuna-type mustard

FallSpring

Ruby Streaks Mustard — Young — Seedling / just planted
Red mustard seedlings (cultivar Red Giant, same species) at the cotyledon stage a week after sowing, already flushed purple the way Ruby Streaks seedlings are.

Species-level photo (not this exact cultivar).

Photo: Goldlocki· CC BY-SA 3.0

Ruby Streaks Mustard — Full grown — What you’re aiming for
A harvest-size bed of red mustard (cultivar Red Giant, same species) showing the dark maroon color Ruby Streaks develops in cool weather; note Red Giant has broad savoyed leaves whereas Ruby Streaks leaves are finely cut like mizuna.

Species-level photo (not this exact cultivar).

Photo: Goldlocki· CC BY-SA 3.0

Planting window · Zone 8a, Decatur

Decatur (Zone 8a): direct sow or transplant from late August through mid-October for fall and winter harvest (a late-October sowing under a low tunnel still yields baby leaves in December), and again from mid-February…

Growing stages

What to look for, and what to do, at each point in its life

This group (mizuna, pac choi varieties Rosie F1, Baby Choi, and Prize Choy, and mustards Ruby Streaks, Red Giant, and Southern Giant) follows the same fall-through-spring rhythm as the other greens in Decatur, sown in September for a winter harvest and again in February-March before spring heat pushes them to bolt, but several of these mustards will happily reseed themselves if you let a plant flower.

1
Sowing
Early-mid September (fall crop) or mid-February to early March (spring crop)

You'll see Seeds are small and round, reddish-brown for mustards and pac choi, and show nothing above ground for several days after sowing.

Do Direct sow 1/4 inch deep, or start pac choi varieties in cell trays for a head start, and keep the surface consistently moist.
2
Seedling
Days 4-18 after sowing

You'll see Round seed leaves appear first, then true leaves show each variety's character: mizuna's deeply feathered leaf, pac choi's smooth spoon shape, and the mustards' ruffled, sometimes reddish-purple edges (Ruby Streaks and Red Giant color up early, even as seedlings).

Do Thin to 4-6 inches apart for mizuna and mustards, 6-8 inches for pac choi, and watch for flea beetle shot-holes.
3
Transplant
3-4 weeks after starting indoors, when seedlings have 2-3 true leaves

You'll see Transplant-ready pac choi seedlings are compact, 2-3 inches tall, with a small but well-formed rosette and a root ball that holds together.

Do Harden off over 5-7 days, then set plants at the same depth they grew, spaced 8-10 inches apart for pac choi in beds or grow bags.
4
Cut-and-come-again harvest
Starting 25-40 days after sowing, continuing 4-8 weeks

You'll see Leaves reach 4-8 inches, with pac choi forming a loose vase-shaped rosette and mustards and mizuna forming a spreading clump of individual leaves.

Do Harvest outer leaves first, or shear the whole plant an inch above the crown for a quick regrow.
5
Bolting
Late spring, typically May, once daylength lengthens and temperatures push past 75-80°F

You'll see A central stalk shoots up, leaves become sparse and pointed, and small yellow four-petaled flowers cluster at the top, a classic mustard-family (Brassica) bloom.

Do Harvest what you can before leaves turn bitter, then either pull the plant or leave a few to flower for pollinators and seed.
6
Seed saving
4-8 weeks after bolting, once seed pods dry from green to brown

You'll see Flower stalks turn from bright yellow blooms to slim, brown, brittle pods that rattle with seed when dry.

Do Cut dry seed stalks into a paper bag, finish drying, then crush and winnow to collect seed; note which varieties are worth saving.

Techniques — transplant, prune, propagate, divide, seed

At a glance

Botanical name: Brassica juncea 'Ruby Streaks'
Family: Brassicaceae (mustard family)
Type: Cool-season annual leafy vegetable; open-pollinated
Native range: Brassica juncea is an ancient natural hybrid of B. rapa and B.
Hardiness: Zones Grown as an annual in all zones; in Zone 8a a fall, winter (with cover) and early-spring crop
Height: 10-18 in at full size (leaves are cut at 3-6 in for baby leaf); 2-3 ft when it bolts

Sun

Full sun for the deepest maroon color and fastest growth; tolerates part shade (leaves…

Water

Even moisture, about 1 in per week; dry soil makes the leaves tougher and much hotter and…

Spacing

Baby leaf: sow 3-5 seeds per inch (up to 60 seeds per ft in a 2-4 in band), 1/4 in deep,…

Soil

Fertile, well-drained soil rich in organic matter, pH 6.0-7.5.

Care

Sow 1/4 in deep and keep moist; seedlings emerge in 3-7 days and are purple-tinged from the start. Shade or water twice daily for sowings made while it is still hot in early September.
Thin to 6-8 in for full-size plants when seedlings have 3-4 true leaves, or leave dense for baby leaf; the thinnings are salad-ready.
Feed lightly: compost at sowing plus fish emulsion or 1/2 cup blood meal per 10 ft after the first cutting; too much nitrogen makes rank, greener growth.

Good to know

A Frank Morton (Wild Garden Seed, Oregon) breeding original that combines the finely cut mizuna leaf shape with the maroon color and bite of Red Giant mustard; it is a true mustard (Brassica juncea), not a mizuna (B.

Where it fits

A natural partner for green mizuna and lettuce in a cut-and-come-again salad bed; interplant between slower kale and collards, or edge beds and grow bags with it for color.

Harvest

Begin cutting baby leaves at 3-6 in tall, about 3 weeks after emergence, with a knife 1 in above the crown (above the growing point);

In the kitchen

Mild and slightly pungent when young with a horseradish-like zip that grows with leaf size;

Watch for

Flea beetles are the main pest of fall mustards in Georgia; also cabbage worms, diamondback moth, harlequin bugs, aphids, slugs.

Wildlife & pollinators

Host plant for cabbage white, cabbage looper and diamondback moth larvae; spring flowers draw honeybees, native bees and hoverflies.

Toxicity

None known; safe for people and pets as food. The pungent leaves and seeds contain glucosinolates and goitrogens, and large amounts can upset a dog's…

Propagation

Seed; open-pollinated, so seed can be saved from plants that overwinter and flower in spring, isolated from other flowering Brassica juncea (it does…

General Asian Greens / Mustards guide

Transplant in the evening; shade cloth the first 3–5 days if highs are above 85°F.
Row cover (AG-19) from day one keeps cabbage worms, flea beetles and harlequin bugs off — the #1 fall greens fix.
Sow a new short row every 2–3 weeks through October for a continuous harvest.
Harvest outer leaves and let the center keep producing (cut-and-come-again); or cut whole plants 1" above the crown and they'll regrow once.
Mustards and mizuna shrug off frost and freezes into the low 20s; pac choi needs row cover below ~28°F.
Let one plant bolt in spring — the yellow flowers feed bees and the seed comes true for open-pollinated types.

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