Myths About Growing Kohlrabi in Scotland

“Kohlrabi is a root vegetable, like a turnip or swede”

Kohlrabi forms a swollen stem base, often called a bulb, not a root. It develops above the soil surface, unlike turnip or swede, which swell underground.

Our read The confusion is understandable, since it eats and tastes like a turnip and sits low in the bed the same way, but the part you're growing is stem tissue, not root tissue.

What to do: Nothing changes in practice, since the growing advice is similar to a root crop either way, but it's worth knowing when a source talks about root disturbance or transplanting: kohlrabi's swollen part isn't underground, so covering or mounding soil over it doesn't help it the way earthing up helps an actual root or tuber.

“The leaves you trim off kohlrabi are just waste, only the bulb is worth eating”

The leaves can be harvested alongside the bulb, and can be steamed like spinach.

Our read Guides often focus only on the bulb, which is how this idea sticks. The leaf trim is a second crop from the same plant.

What to do: Don't compost the leaf trim from a kohlrabi you're harvesting. Steam or wilt it like spinach or spring greens, the same day if possible, since it won't keep as well as the bulb.

“Purple and green kohlrabi are the same vegetable, just a different colour”

Two independent sources agree on a real growing difference: RHS and Gardener's World both say purple varieties are hardier and slower-growing than green, which matures faster.

Our read Colour looks purely cosmetic on the shelf, but it's tracking a genuine difference in how the plant handles a late or unsettled sowing, which matters more in a Scottish shoulder season than it would somewhere with a longer settled summer.

What to do: Choose green varieties, such as 'Korist', for a fast spring crop, and save purple varieties, such as 'Kolibri', for a late-summer sowing where hardiness through less predictable weather matters more than speed.

“Leave kohlrabi in the ground longer to grow a bigger, better bulb”

All three institutional sources agree: RHS, Garden Organic and Gardener's World each independently say to harvest at golf-ball to tennis-ball size, warning that anything larger turns woody and tough.

Our read It's the same intuition that applies to a squash or a marrow, where bigger genuinely can mean more of the vegetable to use, but kohlrabi runs the other way. This is the rare case where three sources gave us the exact same warning without prompting, which is about as settled as a claim gets.

What to do: Check plants every few days once bulbs start sizing up, since the plants mature quickly. Pull at golf-ball to tennis-ball size rather than waiting for it to look more substantial.

“Kohlrabi only bolts if the weather turns cold”

Bolting has three separate triggers, not one: heat, drought, or cold. The risk is highest in hot, dry conditions, not just a cold snap.

Our read Cold gets blamed because it's the trigger most gardeners have heard of for brassicas generally, but for kohlrabi specifically, a dry hot spell is at least as likely a cause.

What to do: Keep the soil consistently moist through any dry spell, not just in cold weather, since drought stress is named as a bolting trigger in its own right, alongside making the bulb woody.

“Kohlrabi has to go in open ground — it won't work in a pot”

Container growing is a standard alternative, specifically recommended for gardeners short on ground space: a pot at least 30cm wide and deep, in sun or semi-shade, filled with peat-free multi-purpose compost, thinned to 15cm spacing.

What to do: If you don't have a spare bed, use a 30cm-plus pot rather than skipping the crop. It's suggested specifically as a way to grow a quick crop of mini veg.