When to plant Kohlrabi in London

Sow seeds around 21st March - 18th April in drills or short blocks, about 1.5–2 cm deep. Sow a little at a time every 21 days for a steady run of crops rather than one large batch.

From 4th April, thin seedlings so the strongest plants are left at 25 cm apart. Keep the soil lightly moist so the remaining plants keep moving without checking.

From 21st March, cover the bed with fine mesh to keep out cabbage white butterflies and pigeons. Fit brassica collars snugly at the stem base to cut cabbage root fly damage, and check the netting after strong wind.

From 11th April to 11th July, feed every 28 days with a nitrogen-rich fertiliser and keep the bed evenly watered. A steady feed helps the swollen stems bulk up without turning pithy.

Start lifting or cutting from 16th May once the swollen stems are about 5–8 cm across and still tender. Pick over the crop through 11th July, because older plants soon become woody and splitting is more common after dry spells.