The swede (Brassica napus), called rutabaga in North America, appeared in Sweden in the 1600s as a cross between cabbage and turnip, which is why the English name is short for Swedish turnip. It needs 90 to 110 days and, in most of the UK and northern Europe, is sown later than almost anything else in the vegetable garden. That sowing date is also the most common reason the crop fails.
Sow in June, not May
Sow directly in place from late May to mid-June. Sow earlier and two things happen: the plant runs to flower instead of forming a root, and the root turns woody and coarse before harvest.
Depth: 2 cm.
Row spacing: 40 to 50 cm.
Germination: 5 to 10 days at 12 to 18 °C.
Harvest: October, that is 90 to 110 days after sowing.
Direct sowing is better than raising plants in modules, because the taproot does not tolerate being disturbed. There is more on the technique in the guide to direct sowing.
Thin out, or you get nothing
This step is skipped more often than any other, and without it you get a row of small hard roots.
Thin in two rounds. First to 10 cm when the plants have two seed leaves, then to 25 to 30 cm when they are the height of a palm. A finished swede weighs 500 g to 1.5 kg, and it needs that room.
The thinnings can be eaten as leafy greens.
Soil and lime
Deep, humus-rich soil that holds moisture. Swede takes a heavier soil than most root crops and copes well with clay.
pH should sit between 6.5 and 7. Acidic soil raises the risk of clubroot, the fungus that gives knobbly, swollen roots and then stays in the soil for decades. Lime in the autumn the year before, not at the same time as you sow.
Do not grow brassicas on the same ground more often than every fourth year.
Even watering, or the root splits
Swede needs even moisture all the way. If it dries out and then gets a lot of water, the root splits lengthways and the flavour turns coarse.
Water deeply once a week rather than a little every day, and cover the soil with grass clippings or straw in July.
Brown heart comes from a shortage of boron
If you cut a swede open and find brown, glassy patches in the middle, it is not rot but a shortage of boron. The root is bitter and unusable.
The problem turns up on light, sandy soils and on soils that have been limed too hard, because a high pH locks the boron up. The remedy is to supply boron through a complete fertiliser with micronutrients or through seaweed, and not to over-lime.
Pests
Flea beetles make small round holes in the seed leaves in June and can wipe out a whole sowing. Cover with fleece straight after sowing.
Cabbage root fly lays eggs at the base of the stem and the larvae go for the root. Netting with a 0.8 mm mesh stops both that and the flea beetles.
Cabbage white butterfly takes the foliage in July and August. The full account is in the article on the cabbage white.
The net goes on from sowing and must not rest against the leaves.
Harvest after the first frost
Swede turns sweeter after a few frosty nights, because the plant breaks starch down into sugar as antifreeze. Wait with the harvest until October, but lift the roots before the ground freezes deep.
Twist the tops off rather than cutting them, and leave a couple of centimetres. A cut too close to the root is a way in for rot.
Storage until spring
Temperature: 0 to 4 °C.
Humidity: high. Dry air makes the root shrivelled and tough.
Method: lay the roots in damp sand in a box, or in perforated bags.
Keeps: four to five months, so until March or April.
The thin film of wax on shop-bought swedes is there for the same reason, to slow evaporation. At home damp sand does the same job.
Varieties
Nadmorska: the most common one, yellow-fleshed and a good keeper.
Vige: early and mild, suits a short season.
Wilhelmsburger: an old variety with a green neck and firm flesh.
Helenor: even shape and good resistance to clubroot.
If you want something faster in the same bed, turnip works, and it is ready to lift in six to eight weeks. The full range is among our cabbage seeds, and we go through a close relative in the article on kale.
Author: Emma Vogiatzi
Fact-checked by Erik Hoekstra
Last updated 2026-08-31