Choy sum makes sense for California backyard cooks who want fast Asian greens but keep planting it too late into summer

The Problem

Choy sum makes sense for California backyard cooks who want fast Asian greens but keep planting it too late into summer heat

Plant choy sum in California when the weather is cooling, not when the backyard finally “feels like gardening season.” For most home cooks, the best move is late summer to fall, then again late winter to early spring. Once daytime heat keeps pushing above about 80°F, choy sum bolts fast, gets tough, and gives you flower stalks before you get enough tender greens for dinner.

The mistake is treating choy sum like basil or tomatoes.

It is closer to bok choy, gai lan, mustard greens, and other brassica crops. It wants short days, mild air, steady water, and quick harvests. In a California backyard, especially inland or in a hot valley, that means your useful window can be surprisingly narrow.

Coastal California: - Sow from February to April - Sow again from August to October - You may get away with small successions almost year-round if your summer highs stay under 75°F

Inland Southern California: - Best window is October to February - Try late September only if nights are cooling - Skip direct sowing during June, July, and August unless you use shade cloth and expect smaller harvests

Central Valley and hotter inland zones: - Main window is October to early March - Late summer sowing is risky unless you start under 30% to 40% shade - If a 10-day forecast shows repeated 85°F afternoons, wait

Bay Area and mild zones: - Sow February to May - Sow again August to November - In foggy areas, you can run more frequent small plantings

The practical backyard method is not one big planting.

Do this instead: sow a small patch every 10 to 14 days while the weather is right. A 2-foot by 3-foot bed section can give enough choy sum for a few stir-fries without overwhelming your kitchen. For a household of 2 to 4 people, plant about 12 to 18 plants per round.

Spacing matters if you want tender stems, not tangled seedlings.

- 4 to 6 inches between plants for young, tender harvests - 8 inches if you want thicker flowering stems - Rows 8 to 12 inches apart - Seed depth around 1/4 inch - Germination usually in 3 to 7 days in mild soil

If you scatter seed too thickly, thin early. Crowded choy sum gets skinny, stressed, and more likely to bolt. The thinnings are edible, so do not treat thinning as waste. Toss them into soup, noodles, fried rice, or a quick garlic oil pan.

For California backyard cooks, the temperature number that changes the decision is 80°F.

Below 75°F, choy sum usually behaves. At 75°F to 80°F, it grows fast but needs attention. Above 80°F, especially with warm nights, it often bolts early. Above 90°F, it is usually not worth wasting seed unless you are testing shade.

Bolting is not a total failure, though. Choy sum is grown for its flowering stalks. The problem is premature bolting, when the plant flowers before it has enough leaf and stem mass. You want thick, juicy stems with unopened yellow buds, not tiny stressed plants throwing flowers at 5 inches tall.

Start checking around 25 to 35 days after sowing for baby greens. Expect fuller stalk harvest around 35 to 50 days, depending on variety and weather. Cut when stems are about 6 to 10 inches tall and buds are formed but not fully open. Use a knife or scissors and cut above the base if you want a small second flush.

The best kitchen harvest is usually not the largest plant. It is the one with crisp stems, glossy leaves, and tight buds. If flowers are already wide open, still eat it, but cook it that day. Texture declines fast.

Water is the other place California gardeners lose it.

Choy sum has shallow roots. It does not want to dry hard between waterings. In a raised bed, check the top 1 inch of soil. If it is dry and the weather is warm, water. In mild fall weather, that may be every 2 to 3 days. In a warm spell, it may be daily for seedlings.

- Compost mixed into the top 4 to 6 inches before sowing - Mulch lightly once seedlings are 2 to 3 inches tall

The Result