Pak choi has a reputation as a bolter: one hot, dry spell or one check in growth and the whole row runs to flower. Scotland's cooler, damper summers rarely bring the sustained heat behind most of that, so boltingA plant switching early into flowering and seed production, usually triggered by stress, after which leaves, roots or bulbs turn bitter or unusable. Full page → matters less here than it does further south. The choice between varieties comes down instead to cold-hardiness, disease risk and what you want on the plate.

Quick answer

Glacier is the best all-round choice: the hardiest of the four and bred for the British climate. Summer Breeze for a warm, dry spell or the shortest disease list. Red Choi for red-purple leaves, if you can keep it well watered.

What Scotland means for the choice

Pak choi bolts in response to heat, warm nights averaging above 10–13°C, drought, or the lengthening days of high summer. A Scottish summer rarely brings the first two, but long June days still apply here, so a dry spell or a check in growth can still set it off. That's why heavy bolt-resistance matters less here than cold-hardiness and damp-weather diseases. The pak choi growing guide covers sowing, spacing and harvesting, and the bolting page has the full list of triggers.

The four varieties compared

The RHS recommends all four with its Award of Garden Merit (AGMThe RHS's Award of Garden Merit: a UK-wide trials award for reliable performance, not a Scotland-specific recommendation. Full definition →), a UK-wide award rather than a Scottish one. Hardiness uses the RHS scale: H5 survives a severe UK winter, H3The RHS's H1a–H7 scale for how much cold a plant can survive outdoors, H1a being tender indoor-only and H7 hardy anywhere in the UK. Full definition → only a mild one.

VarietyHardinessGrowing traitDisease and pest risks
GlacierH5 (to -15°C)Bred for the British climate; slower to bolt, long cropping seasonDowny mildew, white blister, club rootA soil-borne fungal disease of the brassica family that swells and distorts roots, and survives in soil for years. Full definition →
Summer BreezeH3 (to -5°C)Good resistance to heat and coldPowdery mildew only
Choko F1The first-generation offspring of two specific, deliberately chosen parent plants, bred for a predictable, uniform result but not worth saving seed from. Full definition →H3 (to -5°C)Tolerates warmer weather; sow May–August, harvest June–OctoberBlack rot, club root, downy mildew, grey mould, leaf spot
Red ChoiH3 (to -5°C)Needs keeping well watered to avoid boltingFlea beetle, aphids, caterpillars, whitefly, cabbage root fly, club root, powdery mildew, downy mildew
A green pak choi plant with white stalks next to a pak choi plant with dark red-purple leaves
Glacier (left), the hardiest of the four, and Red Choi (right), with dark red-purple leaves.

Glacier: the best all-round choice

Glacier is bred to suit the British climate, with slower bolting and a longer cropping season than most pak choi, and it's the hardiest of the four at H5, down to -15°C. Pak choi is a spring-to-autumn crop here, not one you overwinterKeeping a plant alive and intact through the cold months, whether left outdoors, moved under cover, or stored dormant. Full definition →, so that hardiness matters most for pushing a late sowing into a cold autumn under a clocheA small, portable clear cover placed over an individual plant or short row to trap warmth and keep off wind, rain and pests. Full definition → or fleeceA lightweight, breathable fabric laid or draped over plants to trap a little warmth and keep off frost, wind and some flying pests. Full definition →. Its weak spot is damp-weather disease: downy mildew and white blister are both favoured by wet conditions, which Scotland's summers supply.

When another variety wins

Summer Breeze if you're worried about a hot or dry stretch, or want the lowest disease risk: powdery mildew is the only disease listed for it, and none of the damp-driven ones.

Red Choi if you want colour in the plot. Its leaves are dark red to purple on top, with green undersides over fleshy green stems. It needs keeping well watered to avoid bolting, so it asks for a little more attention than the others.

Choko F1 for a single, well-timed summer sowing: it's sown directly from May to August and harvested from June to October. Birds are among its listed pests, so net it against pigeons.

Club root

Pak choi is often treated as less at risk from club root than other brassicasThe cabbage family: cabbage, kale, broccoli, cauliflower, Brussels sprouts, kohlrabi, swede, turnip and more, sharing the same pests, diseases and rotation rules. Full definition →, but Glacier, Choko F1 and Red Choi all list it as a risk. Only Summer Breeze doesn't. If your soil already has club root, Summer Breeze is the safer choice, and the club root page covers rotationMoving each crop family to different ground each year, on a multi-year cycle, so pests and diseases that build up in soil don't get a repeat host. Full definition → and management. Slugs are the other main risk, and no variety resists them.

Common questions

Is pak choi likely to bolt in a Scottish garden?

Less often than further south, but it can. The triggers are heat, warm nights, drought, lengthening days and a check in growth such as transplant shock, and long Scottish June days still count.

What's the difference between Glacier and Summer Breeze?

Glacier is hardier (H5 against H3) and bred for the British climate, with slower bolting. Summer Breeze resists both heat and cold and has the shortest disease list. For most Scottish gardens Glacier is the safer default.

Does Red Choi taste different from green pak choi?

The difference that's described is in the look and texture: dark red-purple leaves over fleshy green stems. No flavour difference is claimed.

Sources

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