← Plant Guides

How to Grow Improved Purple Choy Sum

Wikimedia Commons

Improved Purple Choy Sum

Brassica rapa subsp. parachinensis

vegetable

Improved Purple Choy Sum is a leafy Asian brassica featuring deep purple stems and dark green leaves with tender flowering buds. It's a quick-maturing cool-season crop prized for its tender leaves, stems, and unopened flower clusters that can be harvested and cooked whole. This variety offers better color retention and improved vigor compared to standard choy sum.

When should you plant Improved Purple Choy Sum in your zone?

Get a personalized planting timeline — when to start seeds, transplant, and harvest — based on your USDA zone and local frost dates. Free to start.

Get my Improved Purple Choy Sum timeline →

Example Improved Purple Choy Sum timeline · Pittsburgh, PA (Zone 6b)

  1. Plant Improved Purple Choy Sum

    Around Apr 17

    Near Pittsburgh's average last spring frost.

  2. Tend & protect

    Late spring–summer

    Watering, feeding, and pest-watch reminders.

  3. Harvest Improved Purple Choy Sum

    Around Jun 1

    ≈ 45 days after planting

Sample dates for Pittsburgh, PA. Sign up to get exact Improved Purple Choy Sum dates for your own zip code.

Growing Conditions

☀️
Sun: Full sun to partial shade; 6+ hours of direct sunlight daily
💧
Water: Consistent moisture; keep soil evenly moist but not waterlogged. Water deeply 1-2 times per week depending on weather. More frequent watering during hot spells.
📏
Spacing: 6-8 inches
📅
Days to maturity: 45-60
🌱
Planting depth: 0.5 inches

Soil

Type: Well-draining, fertile loamy soil rich in organic matter
pH: 6.0-7.5
Amendments:
Compost aged manure nitrogen-rich fertilizer bone meal

Growing Zones

Find your zone →

Thrives in zones 3-9; best in cool seasons (spring and fall)

3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a 9b

Sign up free to see if Improved Purple Choy Sum grows in your zone — and get a personalized planting timeline.

Get my Improved Purple Choy Sum timeline →

Growth Stages

1

Seedling

7-14 days

Tiny cotyledons emerge and develop the first true leaves; plant is delicate and small

Keep soil moist but not waterlogged. Provide bright light (indoors under grow lights or outdoors in dappled shade initially). Thin seedlings to proper spacing once they have 2-3 true leaves.

2

Vegetative Growth

2-3 weeks

Rapid leaf development; purple stems elongate and dark green leaves expand; plant becomes bushy

Maintain consistent moisture and cooler temperatures (60-70°F ideal). Apply balanced fertilizer every 2-3 weeks. Ensure adequate sunlight for deep purple coloration. Monitor for pests closely.

3

Flowering Bud Formation

1-2 weeks

Unopened flower clusters (buds) form at leaf axils and stem tips; buds are tight, tender, and purple-tinged

Continue regular watering and feeding. Harvest buds promptly when tight and tender before they open into flowers, as this triggers continuous production. Cool weather extends this stage.

4

Harvest-Ready

1-3 weeks

Entire plant including stems, leaves, and flower buds are at peak tenderness and flavor; buds are plump but unopened

Harvest regularly by cutting stems above a lower leaf node to encourage branching and continued bud production. Morning harvests when buds are firmest offer best quality.

5

Maturation/Bolting

Variable; triggered by heat stress or maturity

If unharvested, flowers open into yellow blooms and stems become tougher and more fibrous

Plant becomes less desirable for eating once flowering occurs, though flowers are edible. Allow to bolt if you want to save seed. Succession plant new crops for continuous harvests.

Companion Planting

Plan your garden →

Plant with:

Garlic onions beets carrots chard spinach chamomile dill mint

Avoid planting near:

Cabbage broccoli kale other brassicas (within same bed) pole beans fennel strawberries

Common Pests

  • Row covers on young plants, neem oil spray, kaolin clay, insecticidal soap. Remove plant debris and use trap crops.

  • Row covers, hand-picking, Bacillus thuringiensis (Bt), neem oil. Monitor undersides of leaves for egg clusters.

  • Strong water spray, insecticidal soap, neem oil, reflective mulches. Encourage beneficial insects like ladybugs.

  • Bacillus thuringiensis (Bt), row covers, spinosad, removal of affected leaves.

  • and

    Handpicking at dusk, beer traps, copper barriers, diatomaceous earth, remove hiding spots and excess moisture.

Uses

🍳

Tender Asian Greens for Stir-Fry & Cooking

Culinary

Improved Purple Choy Sum is prized in Asian cuisines, especially Chinese cooking, where the tender leaves, stems, and unopened flower buds are stir-fried, blanched, or steamed whole. The mild, slightly sweet flavor and tender texture make it a versatile vegetable that cooks quickly. [source]

🍳

Nutritious Green Vegetable with Calcium & Iron

Culinary

Like other brassicas, purple choy sum is nutrient-dense, providing significant calcium, iron, vitamins A and C, and glucosinolates (compounds with potential anti-cancer properties). It's an excellent addition to healthy diets and Asian cuisine. [source]

🏠

Ornamental Garden Appeal

Household

The striking purple stems and dark green leaves add visual interest to vegetable gardens and can be used as an ornamental-edible border plant or in containers. Many gardeners grow it as much for appearance as for culinary use. [source]

🍳

Quick-Harvest Crop for Succession Planting

Culinary

With a 45-60 day maturity and the ability to produce multiple harvests from a single plant, Improved Purple Choy Sum is ideal for succession planting to provide fresh greens throughout the cool season. [source]

🦋

Pollinator Support

Wildlife

If allowed to flower, choy sum produces abundant yellow flowers that attract bees, butterflies, and other beneficial pollinators, supporting garden ecology and biodiversity. [source]

Harvest Tips

Begin harvesting when flower buds are tight and tender, typically 45-60 days from planting. Cut entire flowering stems 4-6 inches from the base just above a leaf node to encourage branching and continued production. Harvest in early morning when buds are firmest and most tender. Regular harvesting delays bolting and extends the productive season. All parts—leaves, stems, and buds—are edible; harvest whole plants or pick outer stems first, leaving inner growth to mature.

Fun Facts

  • 🌱 Improved Purple Choy Sum is native to China and remains a staple in Chinese and Southeast Asian cuisines, often sold fresh in Asian markets. The name 'choy sum' means 'vegetable heart' in Cantonese, referring to the tender new growth.
  • 🌱 Unlike some brassicas, choy sum produces tender, edible flower buds that are harvested before blooming—this mimics the plant's natural strategy of producing new growth to ensure seed production, making continuous harvesting possible.
  • 🌱 The purple pigmentation in the stems comes from anthocyanins, powerful antioxidants also found in blueberries and red cabbage. This improved variety was specifically bred to retain vibrant purple color longer and resist common brassica pests more effectively.

Gardening Terms

New to gardening? Learn about terms used in this guide:

Bolt Full Sun Partial Shade True Leaves
Shop Improved Purple Choy Sum plants and related plants at Plant Addicts →

Join 30,000 gardeners planning their gardens with LizPlants.

Get your personalized Improved Purple Choy Sum planting timeline

Tell us your zip code and we'll calculate exactly when to start Improved Purple Choy Sum seeds, transplant seedlings, and harvest — based on your USDA zone and local frost dates. Includes calendar reminders and printable task lists. Free to start.

Get my Improved Purple Choy Sum timeline →