Bok Choy are one of those crops that reward a little planning before a single seed goes in. Bok choy grows as a neat rosette of crisp white stems and dark green leaves. It prefers part shade, is hardy, and matures in 45–60 days, making it a cool-season crop. The companions you choose decide whether that bed works hard all season or sits half empty while one crop slowly does its thing.
Our crop data lists four companions for bok choy — marigolds, basil, onions and lettuce — and each earns its place for a different reason. Heads are cut whole or the outer stems are picked as needed. This guide covers the four companions, the plants to avoid, and a layout for part shade, soil pH 6.0–7.5 and 45–60 days to maturity.
Best companion plants for bok choy
| Companion | Why it is grown with bok choy |
|---|---|
| Marigolds | Gardeners plant marigolds around brassicas. The strong scent is traditionally said to confuse pests such as cabbage worms that hunt by smell, and the flowers bring in hoverflies that eat aphids. |
| Basil | Basil suits the sunny edge of a brassica bed once frost danger has passed. Its scent is traditionally said to confuse flying pests, and its flowers bring in bees and hoverflies. |
| Onions | Onions are slim and shallow-rooted, so they slot between leafy brassicas without stealing light or deep soil. Their strong smell is traditionally said to confuse pests such as cabbage worms. |
| Lettuce | Lettuce grows in the shade of leafy brassicas and is cut before the main crop closes over. It uses the lower layer of the bed and shades the soil. |
None of the four fights bok choy for the same layer of the bed: marigolds and basil work the sunny edges, onions use the shallow soil between plants, and lettuce fills the gaps and is gone before the main crop needs the room.
If you only have room for one companion, plant marigolds: they are the most forgiving of the four and flower for months. If you have room for two, add lettuce — it is ready in weeks and turns empty gaps into food while you wait for the main crop.
How companion planting works
Companion planting is not magic. Some pairings help a little, in specific ways, and the best gardeners use them as one tool among many — alongside rotation, spacing, watering and keeping the bed clean.
The first principle is pest confusion. Many pests find their host plant by smell, and a strongly scented neighbour such as marigolds, basil or onions is traditionally said to make the crop harder to find. That is a traditional claim, not a proven guarantee: it may reduce damage, it will not eliminate it.
The second principle is pollinator attraction. Flowers such as marigolds and basil, once they bloom, bring bees and hoverflies into the bed — and hoverfly larvae eat aphids. Let a little basil flower rather than pinching every stem.
The third principle is nitrogen fixing by legumes. Peas and beans work with soil bacteria to fix nitrogen from the air. None of the four companions listed for bok choy is a legume, so do not expect a nitrogen boost from this pairing.
The fourth principle is ground cover. A low, fast crop such as lettuce shades bare soil, holds moisture in, and suppresses weeds — which matters for a crop with moderate water needs growing in part shade. A living mulch does the same job as straw, and you can eat it.
Plants to avoid near bok choy
The crops to keep away from bok choy are its own relatives. Bok Choy belong to the Brassicaceae family, and plants in the same family tend to attract the same pests and suffer the same diseases — in this case cabbage worms, aphids, flea beetles, slugs. Planting relatives side by side gives those pests a continuous buffet and leaves the same nutrients depleted in one patch of soil. So do not plant bok choy next to Broccoli, Cauliflower, Cabbage, Kale, Radishes, Turnips, Brussels Sprouts, Collard Greens, or the other Brassicaceae relatives in the garden, and do not follow bok choy with any of them in the same bed next year. Rotate the whole family to a fresh bed instead.
Planting layout and spacing
| Growing factor | What bok choy need |
|---|---|
| Sun | part shade |
| Soil pH | 6.0–7.5 |
| Days to germination | 7–10 |
| Days to maturity | 45–60 |
| Spacing | 8–12 inches |
| Water needs | moderate |
| Cold tolerance | hardy |
| Sowing method | both |
| Family | Brassicaceae |
Start with the spacing: bok choy need 8–12 inches between plants, and that figure is for the mature plant, not the seedling. Mark the rows out before you sow, and use our plant-spacing calculator or the square-foot garden planner to work out how many plants your bed holds. Crowding is the commonest mistake in a companion bed.
Put the companions where they belong: marigolds at the ends of rows and along the sunny edge, basil at the sunniest edge after the last frost, onions tucked between plants, and lettuce filling the gaps in succession. Nothing should be planted so close that it shades bok choy or blocks airflow — damp, still air is where disease starts.
Aim for a soil pH of 6.0–7.5, with plenty of well-rotted compost worked in before planting. Water needs are moderate, so keep the soil evenly moist and mulch to hold that moisture in. The watering calculator gives a starting point for your bed size.
Common problems and fixes
| Problem | What to do |
|---|---|
| Cabbage worms | Check leaf undersides weekly, pick caterpillars off by hand, and cover the bed with fine insect mesh. |
| Aphids | Spray off with a strong jet of water, encourage ladybirds and hoverflies, and remove badly curled leaves. |
| Flea beetles | Cover young plants with fine mesh, keep the soil moist, and mulch to reduce the dry conditions they favour. |
| Slugs | Water in the morning, clear debris where slugs hide, and hand-pick at dusk or set simple beer traps. |
| Bolting in hot weather | Keep the soil cool and moist with mulch, and sow for the cool part of the season. |
| Small or loose heads | Give each plant its full spacing and steady water; crowding is the commonest cause. |
Cabbage worms
Cabbage worms are listed among the common pests of bok choy in our crop data, so check for them weekly rather than waiting for visible damage. Check leaf undersides weekly, pick caterpillars off by hand, and cover the bed with fine insect mesh.
Aphids
Aphids are the second pest to watch for on bok choy. Spray off with a strong jet of water, encourage ladybirds and hoverflies, and remove badly curled leaves.
Flea beetles
Flea beetles are another problem that shows up on bok choy, often a sign of the growing conditions rather than bad luck. Cover young plants with fine mesh, keep the soil moist, and mulch to reduce the dry conditions they favour. If it keeps returning in the same bed, rotate bok choy to a fresh bed next year. Our pest-identifier helper can help confirm what you are looking at.
Frequently asked questions
What is the best companion plant for bok choy?
Marigolds are the safest first choice: they suit every bed and flower all season. After them, pick from the table above — lettuce for quick gaps, onions for narrow edges, basil for a sunny border.
Can I plant bok choy with lettuce?
Yes. Lettuce is listed as a companion for bok choy in our crop data, and it is one of the most useful gap-fillers in the garden. Sow it between the plants, cut it young, and it will be finished before the main crop needs the space.
What should I not plant near bok choy?
Avoid its own family. They share the Brassicaceae family, so they share the same pests (cabbage worms, aphids, flea beetles, slugs) and the same soil demands. Keep the family apart in the same season and rotate it to a different bed next year.
How far apart should I plant bok choy and its companions?
Give bok choy its full spacing of 8–12 inches — crowding is the commonest cause of small harvests. Companions go in the gaps, at the edges or between rows, but never so close that they shade or crowd the main crop. Our plant-spacing calculator works out how many plants fit your bed.
When should I plant the companions?
Sow or set out the companions at the same time as the main crop, or just after. Marigolds and basil are tender, so they go in after the last frost, even if the main crop went in earlier. Check dates with our frost-date calculator.