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How to Grow Kohlrabis Canada | Care, Pests & Disease Control

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Kohlrabi (Brassica oleracea Gongylodes Group)

Young kohlrabi seedlings growing in a tray — “Kohlrabi EPT-Jungpflanzen-2--Josef Schlaghecken” by Schlaghecken Josef is licensed under CC BY-SA 4.0. Source: Wikimedia Commons

11 sources cited · Verified

The short answer

Ready in
42–84 days
Site
soil pH 6–6.5
Biggest risk
Brassica downy mildew

In the UK, kohlrabis are ready to harvest 42–84 days after planting.

Kohlrabis (Brassica oleracea Gongylodes Group) — biennial, grown as annual.

This crop carries an unusually heavy problem load: 3 diseases, 5 pests and 0 nutrient issues are documented for it, so most of the effort in growing it well goes into prevention.

Core growing advice on this page is checked against named horticultural and university-extension sources — see References.

Diseases

Young kohlrabi seedlings growing in a tray — “Kohlrabi EPT-Jungpflanzen-2--Josef Schlaghecken” by Schlaghecken Josef is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Kohlrabi EPT-Jungpflanzen-2--Josef Schlaghecken” by Schlaghecken Josef is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.
Brassica downy mildew

Hyaloperonospora brassicae (syn. Peronospora parasitica)

White blister

Albugo candida

Plasmodiophora brassicae

Pests

Young kohlrabi seedlings growing in a tray — “Kohlrabi EPT-Jungpflanzen-2--Josef Schlaghecken” by Schlaghecken Josef is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Kohlrabi EPT-Jungpflanzen-2--Josef Schlaghecken” by Schlaghecken Josef is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.
Slugs

Gastropoda (slugs, various spp.)

Cabbage root fly (US: cabbage maggot)

Delia radicum

Cabbage caterpillars

Pieris brassicae; Pieris rapae; Pieris napi; Mamestra brassicae; Plutella xylostella

Flea beetles

Chrysomelidae: Alticini (various spp.)

Mealy cabbage aphid

Brevicoryne brassicae

Quick Facts

A purple kohlrabi globe growing in the ground — “Brassica oleracea var. gongylodes 01” by Σ64 is licensed under CC BY 4.0. Source: Wikimedia Commons
“Brassica oleracea var. gongylodes 01” by Σ64 is licensed under CC BY 4.0. Source: Wikimedia Commons.
Factor Value
Soil pH 6 - 6.5
Optimal growing temp 12-18C
Minimum survivable temp -2C
Time to harvest 42-84 days
Drainage Chalk, Loam, Clay, Sand; fertile, moisture-retentive soil, less nitrogen-demanding than other brassicas
Lifecycle biennial, grown as annual
Edible parts swollen stem, young leaves

At a Glance

A purple kohlrabi globe growing in the ground — “Brassica oleracea var. gongylodes 01” by Σ64 is licensed under CC BY 4.0. Source: Wikimedia Commons
“Brassica oleracea var. gongylodes 01” by Σ64 is licensed under CC BY 4.0. Source: Wikimedia Commons.
Brassica oleracea Gongy… Kohlrabi Brassica downy mildew White blister Club root Slugs Cabbage root fly (US: c… Cabbage caterpillars Flea beetles Mealy cabbage aphid DISEASES PESTS

Soil & Growing Conditions

Young kohlrabi seedlings growing in a tray — “Kohlrabi EPT-Jungpflanzen-2--Josef Schlaghecken” by Schlaghecken Josef is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Kohlrabi EPT-Jungpflanzen-2--Josef Schlaghecken” by Schlaghecken Josef is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.

Soil pH range

6 6.5

Span reflects genuine variation between the cited authorities, not a single agreed figure.

Growth Stages

A bolted kohlrabi plant in flower — “Brassica oleracea gongylodes without sun” by Crusier is licensed under CC BY-SA 3.0. Source: Wikimedia Commons
“Brassica oleracea gongylodes without sun” by Crusier is licensed under CC BY-SA 3.0. Source: Wikimedia Commons.
Stage BBCH Notes
Sowing and germination 0 Sow 1.5cm deep, indoors in spring for transplanting 3-4 weeks later, or outdoors March-July (August in mild areas) once soil exceeds 10C; germinates in under 2 weeks (RHS).
Thinning and establishment 1 Thin to a final spacing of 15cm apart in rows 30cm apart once seedlings reach 2.5cm tall or show their first true leaves; water regularly until well rooted (RHS).
Stem swelling 4 Keep soil consistently moist -- drought causes woodiness and bolting; hand-weed near plants to avoid damaging the swelling stem; protect with insect-proof mesh and against slugs/snails (RHS).
Harvest 8 Harvest once the swollen stem is between golf-ball and tennis-ball size for best tenderness; larger specimens turn woody. Harvest window runs May-November, or into December in milder areas (RHS).

Harvest & Storage

A pair of harvested green kohlrabi — “A pair of cabbage turnips in home” by Peachyeung316 is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“A pair of cabbage turnips in home” by Peachyeung316 is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.

When to pick: Harvest when young, between golf-ball and tennis-ball size (5-6cm diameter); larger specimens lose flavour and turn woody, especially in hot dry weather

References

  1. country=USA

  2. country=INTL

  3. country=UK

  4. country=UK

  5. country=UK

  6. country=UK

  7. country=UK

  8. country=UK

  9. country=UK

  10. Directly fetched and verified (canonical URL differs from requested URL /biodiversity/slugs -> redirects to /biodiversity/slugs-and-snails). RHS explicitly advises against slug pellets (even organic) due to wildlife harm, and cites RHS's own controlled trial finding no damage reduction from physical barriers (copper tape, bark mulch, eggshell, grit, wool) -- while also noting some other studies have shown copper barriers to repel slugs, a preserved disagreement rather than a silently resolved one. Details Nemaslug (Phasmarhabditis hermaphrodita) biological control including application temperature range and its lack of effect on snails specifically.

  11. country=USA

11 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.

Frequently Asked Questions

How long do kohlrabis take to grow?

Typically 42–84 days, depending on cultivar and growing conditions.

What soil pH do kohlrabis need?

A pH of about 6–6.5. That span reflects genuine variation between the authorities we cite rather than a single agreed figure — the References section lists each source's exact range.

What problems affect kohlrabis?

Our data links 3 diseases and 5 pests to this crop. See the sections above for each one and how to manage it.

Plan next season before the problems start

Short-season growing is arithmetic before it is technique: days to maturity against frost-free days decides what will finish at all. The Canada Garden Planner does that subtraction for your region before you sow.

Get the Canada Garden Planner →

Instant PDF download · Written for Canadian growing conditions

SoilCommander Editorial Team

Canadian vegetable growing guides · Checked against provincial agriculture & university extension guidance

Every SoilCommander guide is written and maintained by our editorial team for real Canadian growing conditions, and checked against provincial agriculture and Canadian university extension guidance, and against frost-date and growing-season data, before publication.

Vegetable Growing Guides Canada

Last verified 2026-08-30

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