Green 70 D Improved
Brassica rapa var. chinensis
Wikimedia Commons
Very similar to Gunsho, just a few days later to mature. Choi sums are among the most popular vegetables in Hong Kong, Taiwan, and China. The stems are a vibrant bright green, very sweet and tender, and are usually harvested just before, or as the first few buds are opening. The stems regrow for cut-and-come-again harvest. Excellent in stir-fries, steamed, or in soups.
Harvest
21d
Days to harvest
Sun
Full sun to part shade
Zones
5–9
USDA hardiness
Height
3 feet
Planting Timeline
Showing dates for Green 70 D Improved in USDA Zone 7
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Green 70 D Improved · Zones 5–9
Growing Details
Zone-by-Zone Planting Calendar
| Zone | Indoor Start | Transplant | Direct Sow | Harvest |
|---|---|---|---|---|
| Zone 3 | — | — | May – June | May – October |
| Zone 4 | — | — | April – June | May – October |
| Zone 5 | — | — | April – May | May – November |
| Zone 6 | — | — | April – May | April – November |
| Zone 7 | — | — | March – May | April – November |
| Zone 8 | — | — | March – April | March – December |
| Zone 9 | — | — | February – March | February – December |
| Zone 10 | — | — | January – March | February – December |
| Zone 1 | — | — | June – July | June – September |
| Zone 2 | — | — | May – July | June – September |
| Zone 11 | — | — | January – February | January – December |
| Zone 12 | — | — | January – February | January – December |
| Zone 13 | — | — | January – February | January – December |
Succession Planting
Green 70 D Improved hits harvest in about 21 days, which makes it one of the faster-cycling crops in the garden and a natural fit for tight succession planting. In zone 7, direct sow every 14 days starting March 1 and continue through early May for a spring run. Pick back up again in late August and sow every 14 days through early October — the plant handles light frost down to around 28°F, so fall sowings can stretch your harvest into November.
Stop spring sowings once daytime highs are consistently above 80°F; at that point bolting and tip burn will outpace your harvest window. A 14-day cadence means you'll have 3–4 rows at different stages at any given time, which is exactly what a CSA box needs when you're pulling cuts every week.
Complete Growing Guide
Very similar to Gunsho, just a few days later to mature. Choi sums are among the most popular vegetables in Hong Kong, Taiwan, and China. The stems are a vibrant bright green, very sweet and tender, and are usually harvested just before, or as the first few buds are opening. The stems regrow for cut-and-come-again harvest. Excellent in stir-fries, steamed, or in soups. According to Johnny's Selected Seeds, Green 70 D Improved is 21 baby; 42 full size to maturity, annual, open pollinated. Notable features: Cold Tolerant, Heat Tolerant.
Light: Full sun (6 or more hours of direct sunlight a day), Partial Shade (Direct sunlight only part of the day, 2-6 hours). Soil: Clay, Loam (Silt), Sand. Soil pH: Acid (<6.0), Neutral (6.0-8.0). Drainage: Good Drainage, Moist. Height: 0 ft. 10 in. - 2 ft. 0 in.. Spread: 1 ft. 0 in. - 2 ft. 0 in.. Spacing: 12 inches-3 feet. Growth rate: Medium. Maintenance: Medium. Propagation: Seed, Stem Cutting. Regions: Coastal, Mountains, Piedmont.
Harvesting
Green 70 D Improved reaches harvest at 21 baby; 42 full size from sowing per Johnny's Selected Seeds. As an annual, harvest continues until frost ends the season.
The fruits dry and split when ripe.
Color: Brown/Copper, Green. Type: Siliqua. Length: > 3 inches.
Garden value: Edible
Harvest time: Fall, Summer
Bloom time: Spring, Summer
Edibility: The foliage is edible raw or cooked but when cooked can emit an unpleasant odor.
Storage & Preservation
Store freshly harvested Green 70 D Improved leaves in a perforated plastic bag at 32–40°F with 95% humidity; a refrigerator crisper drawer works well. Under these conditions, expect 7–10 days of acceptable freshness before wilting accelerates. For longer preservation, blanch whole leaves for 2–3 minutes, cool rapidly in ice water, then freeze in airtight containers or vacuum-seal bags for up to three months. Fermenting is also viable: layer chopped leaves with 2–3% salt by weight in a clean jar, press to submerge under brine, and ferment at room temperature for two weeks. Because this variety matures quickly at 21 days, successive plantings allow continuous fresh harvest rather than relying on storage. Avoid washing until just before use, as excess moisture speeds decay.
History & Origin
Green 70 D Improved is open-pollinated, meaning seed saved from healthy plants will produce true-to-type offspring. Listed in the Johnny's Selected Seeds catalog.
Brassica is a genus of plants in the cabbage and mustard family (Brassicaceae). The members of the genus are informally known as cruciferous vegetables, cabbages, mustard plants, or simply brassicas. Crops from this genus are sometimes called cole crops—derived from the Latin caulis, denoting the stem or stalk of a plant.
Advantages
- +Matures in just 21 days, enabling multiple harvests per growing season
- +Cut-and-come-again regrowth allows extended harvesting from single planting
- +Vibrant green stems stay sweet and tender when harvested at peak
- +Versatile in stir-fries, soups, and steamed preparations for Asian cuisine
- +Only slightly later than Gunsho with similar quality and vigor
Considerations
- -Requires consistent moisture; drought stress causes premature bolting and bitterness
- -Prefers rich soil with good drainage; struggles in poor or compacted beds
- -Susceptible to flea beetles and cabbage loopers in outdoor growing conditions
Companion Plants
Radishes are probably the most practical companion for Green 70 D Improved in a tight row. They germinate fast — often up in 5–7 days — and you can pull them well before this bok choy needs its full 6–8 inch spacing. More usefully, radishes draw flea beetles away from the brassica leaves; the beetles will work the radish foliage first and leave your bok choy alone long enough to size up. Marigolds — specifically Tagetes patula, the French dwarf type — planted at the bed edges have documented root secretions that suppress root-knot nematodes (Meloidogyne spp.), which can be a genuine problem in Georgia's sandier soils. Chives and garlic work on a different mechanism: their sulfur compounds disrupt the olfactory cues that aphids use to locate brassica crops. In zone 7 Georgia, aphid pressure on bok choy tends to spike in April when temperatures swing between 50°F nights and 75°F days, so having alliums nearby during that window is worth the bed space.
Broccoli is the companion to skip. Both it and Green 70 D Improved are heavy feeders pulling hard on the same nitrogen and calcium reserves, and they'll undercut each other at the root level when planted within 12 inches. Walnut trees are a harder problem: black walnut (Juglans nigra) produces juglone through its roots and decomposing leaf litter, and most brassicas — including this one — will stunt or fail outright inside the drip line. If you've got one on the property, this crop needs to be well clear of it.
Plant Together
Chives
Repels aphids and improves lettuce flavor while providing natural pest deterrent
Carrots
Deep roots don't compete with shallow lettuce roots and help break up soil
Radishes
Quick-growing companion that loosens soil and deters flea beetles
Marigolds
Repels nematodes, aphids, and other harmful insects through natural compounds
Spinach
Similar growing requirements and provides ground cover to retain soil moisture
Garlic
Deters aphids, slugs, and other pests while not competing for space
Nasturtiums
Acts as trap crop for aphids and cucumber beetles, drawing pests away from lettuce
Dill
Attracts beneficial insects like ladybugs and lacewings that control aphids
Keep Apart
Broccoli
Competes for similar nutrients and can shade lettuce, reducing growth
Sunflowers
Allelopathic compounds inhibit lettuce germination and growth
Walnut trees
Produces juglone toxin that severely stunts or kills lettuce plants
Nutrition Facts
Per 100g serving. % Daily Value based on 2,000 calorie diet. Source: USDA FoodData Central (FDC #2346388)
Troubleshooting Green 70 D Improved
What you'll see, why it happens, and what to do about it.
Seedlings collapse at the soil line within the first 7–10 days after direct sowing — stems look pinched or water-soaked at the base
Likely Causes
- Damping off — a fungal complex (commonly Pythium spp. or Rhizoctonia solani) that thrives in cool, wet, poorly-drained soil
- Overwatering or compacted seedbed that holds moisture too long
What to Do
- 1.Don't replant into the same spot immediately — NC State Extension's IPM case study on lettuce seedling death points to soil history as a key factor; rotate to a fresh bed or container with new mix
- 2.If you're starting in trays, use a sterile seed-starting medium and make sure drainage holes aren't blocked
- 3.Let the soil surface dry slightly between waterings once seeds have germinated — consistent moisture doesn't mean constantly saturated
White fuzzy growth on the soil surface around seedlings, with no obvious insect damage visible
Likely Causes
- Saprophytic mold or Pythium-related damping off — the fuzzy mycelium is a visible sign of fungal activity in wet, organic-rich soil
- Mulch or organic matter sitting directly against the stem base, trapping humidity
What to Do
- 1.Pull back any mulch from within 1 inch of the stem base
- 2.Improve airflow by thinning seedlings to the recommended 6–8 inch spacing as soon as they're large enough to handle
- 3.Top-dress the immediate area with a thin layer of coarse sand or perlite to break the moisture seal at the soil surface
Leaves turning pale or bleached at the center, especially during stretches above 85°F in late spring
Likely Causes
- Tip burn — a calcium-uptake disorder triggered by rapid transpiration in heat, not a true nutrient deficiency
- Planting too late into the warm season; Green 70 D Improved matures in 21 days but still suffers when sustained heat arrives before harvest
What to Do
- 1.Shift succession sowings earlier — in zone 7, aim to have your last spring sowing in the ground by early May so heads finish before daytime highs lock in above 85°F
- 2.Water consistently in the early morning; irregular watering interrupts calcium movement through the plant
- 3.Drape 30–40% shade cloth over the bed once afternoon temps regularly hit the low 80s
Ragged holes in outer leaves overnight, with silvery slime trails visible in the morning
Likely Causes
- Slugs (Deroceras reticulatum and related species) — extremely common on leafy brassicas and bok choy types in shaded, moist beds
- Evening overhead irrigation, which gives slugs ideal conditions all night long
What to Do
- 1.Switch watering to early morning so the soil surface dries by nightfall
- 2.Sink shallow traps — a tuna can flush with the soil surface, filled with cheap beer; check and empty every 2–3 days
- 3.Sprinkle food-grade diatomaceous earth around the bed perimeter after a dry spell and reapply after rain
Frequently Asked Questions
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Growing Guides from Wind River Greens
Where to Buy Seeds
Sources & References
External authority sources used in compiling this guide.
- BreederJohnny's Selected Seeds
- USDAUSDA FoodData Central
See the Methodology page for how this data is sourced, what's AI-assisted, and known limitations.