Swede (rutabaga in North America) looks and cooks like a bigger, denser cousin of turnip, but botanically it's a genuinely different species -- Brassica napus rather than turnip's Brassica rapa -- and it doesn't cross with turnip or any of this site's other brassicas (all a third species, Brassica oleracea). It's also a living larder like parsnip, but only in mild zones -- swede is cold-tolerant, not extreme, and colder zones need to treat it more like carrot: lift before a hard freeze and store in sand.
Water need
Inconsistent watering is the main cause of woody texture and can trigger premature bolting -- keep moisture even through dry spells.
Calories at a glance
370 kcal/kg -- modest, similar to turnip and below the other root vegetables covered so far (scale is log-based across all 55 crops in the calculator).
Temperature Range by Month
Month on the bottom, temperature up the side. The pale green background is what the plant can survive at all -- fatal above or below it, labelled directly on the chart where that applies to your zone. The coral band is its ideal range, and only fades in during the months this zone would actually have the crop in the ground -- reusing the exact same sowing/harvesting data as the calendar further down the page. The blue line is real monthly climate data (not a modelled estimate) for a representative rural/agricultural location in this zone -- a small farming town or agricultural research station rather than a major city, to avoid the warmer bias city weather stations have. For the actual verdict on how well this crop does in your zone, see the badge at the top of the page -- that's based on the site's own researched yield figures, not this chart.
Quick Start: Sowing to Harvest
- Sow direct. Swede doesn't transplant well -- sow direct into the bed it will grow in, in soil that's had recent lime or isn't acidic, since acidic soil increases the risk of clubroot.
- Thin to final spacing. Thin to around 20-25cm apart once seedlings are established -- swede needs more room than turnip to bulk up to full size.
- Tend through the season. Keep watering even, especially in dry spells -- inconsistent moisture leads to woody texture and can trigger premature bolting.
- Harvest once sized, or leave standing in mild zones. Roots are ready from tennis-ball size upward. In mild zones, leave them in the ground and dig as needed through winter; in colder zones, plan to lift before the ground freezes solid.
- Store in sand if your zone needs it. Where the ground does freeze hard, lift before that happens, twist off the tops, and layer the unwashed roots in slightly damp sand in a cool shed or cellar.
Sowing & Harvesting Calendar
Pick your zone under "Temperature Range by Month" above and this updates too. The Sow row: green is the normal safe sowing window, amber is pushing the season by roughly a month either side, blue is an even earlier under-glass start. The Harvest row has two shades: solid green is the main harvest window, while the striped tail reflects the living-larder option covered in Storage & Preservation below -- remember that tail is only realistic in your zone's milder winters, not everywhere it appears.
Calories & Yield
Swede is a modest calorie crop at about 370 kcal per kg -- similar to turnip, below the other root vegetables covered on this site. Maritime and Continental zones give the best yields here.
| Climate Zone | Yield per plant | Calories per plant | Viability |
|---|---|---|---|
| Tropical / Humid | -- | -- | Not viable |
| Subtropical | 0.5 kg | 185 kcal | Viable |
| Mediterranean | 0.6 kg | 222 kcal | Viable |
| Temperate Maritime | 0.7 kg | 259 kcal | Viable -- best yield |
| Temperate Continental | 0.7 kg | 259 kcal | Viable -- best yield |
| Cool / Boreal | 0.5 kg | 185 kcal | Viable |
| Arid / Semi-Arid | -- | -- | Not viable |
| Highland / Alpine | 0.4 kg | 148 kcal | Viable |
Figures per plant sown, from the site's own crop database.
Varieties Worth Knowing
Swede has fewer named varieties in wide circulation than most root crops, but they still differ meaningfully on disease resistance and winter hardiness. All the varieties below are open-pollinated (OP), meaning seed saved from them breeds true and is worth keeping under this site's seed-saving approach; none are F1 hybrids.
Seed Saving -- Quick Guide
Swede is a different species from cabbage and kale, so it won't cross with them -- but it shares a species with oilseed rape, which means gardens near farmland face a crossing risk most people don't expect.
SERVINGS, NOT DAILY CALORIES This works out plate-sized servings of swede from your seed during its fresh harvest window only, not your group's full daily calorie needs. For that, use the main calculator.
BIENNIAL Swede is a biennial, not an annual -- it doesn't produce seed in its first year. Roots grow in year one, a few overwintered roots flower and set seed in year two, and that seed is only ready to sow in year three. If you're starting from scratch with no ongoing seed supply, that means having enough seed on hand for both year one's and year two's sowing up front. Plan for roughly double the seed quantity below if that's your situation.
Estimated for your selected zone above, using this site's own germination, loss and yield figures for swede -- a helping is roughly what you'd put on a plate as part of a meal with other veg. Treat it as a planning estimate, not a promise.
Storage & Preservation
The site's own crop data calls swede a living larder that rarely freezes solid in mild zones -- meaning in those zones, roots can simply be left in the ground and dug as needed right through winter, the same as parsnip. Check your own zone's calendar above: a long striped harvest tail means this is realistic for you.
In colder zones where the ground genuinely does freeze solid, treat swede like carrot instead: lift before the hard freeze, twist off the tops, and layer the unwashed roots in slightly damp sand in a cool shed or cellar, where they'll keep for several months.
Growing Swede Without Bought Inputs
Swede shares the same pest pressure as this site's other brassicas -- flea beetle on young seedlings and cabbage root fly at the base of the stem are the two to watch for.
Fine mesh or fleece from sowing onward is the single most effective input-free defence against both -- it physically excludes the adult insects before they can lay eggs.
Non-acidic soil matters more for swede than most crops here -- acidic conditions increase the risk of clubroot, a serious soil-borne disease with no cure once established. Liming acidic soil ahead of planting is a real preventative step.
Crop rotation reduces clubroot and other soil-borne brassica problems building up -- avoid growing swede or any other brassica in the same spot two years running.
Frequently Asked Questions
Does swede cross-pollinate with turnip or the other brassicas on this site?
No -- despite the family resemblance, swede is genuinely a different species (Brassica napus) from both turnip (Brassica rapa) and the kale/cabbage/broccoli/cauliflower/Brussels sprouts/kohlrabi group (all Brassica oleracea). Different species don't cross under normal garden conditions, so swede can flower for seed without worrying about anything else in this database.
What does swede actually need isolating from, then?
Other Brassica napus -- other rutabaga varieties, and rapeseed/canola if it's grown as a field crop nearby. Neither is a site crop here, so in practice most home gardeners only need to worry about isolating different swede varieties from each other.
How cold and hot can swede survive?
Roughly -10°C to 29°C (14°F to 84°F), with ideal growth in the 10-21°C range and flavour improving after light frost. It's genuinely cold-tolerant, but noticeably less extreme than parsnip -- swede's own crop data specifically notes it rarely freezes solid only in mild zones, not everywhere.
Can I leave swede in the ground over winter like parsnip?
In mild zones, yes -- the site's own crop data models it as a living larder there too. In colder zones where the ground genuinely freezes solid, that's not reliable, and lifting before the hard freeze and storing in sand is the safer approach. Check your zone's calendar above for how long a harvest window you actually get.
Is swede a good calorie crop for self-sufficiency?
Modest -- around 370 kcal per kg, similar in scale to turnip and below carrot, beetroot or parsnip. Best treated as a filling winter vegetable and nutritional variety rather than a calorie strategy on its own.
Do I need pesticides to grow swede?
No. Swede shares brassica pests like flea beetle and cabbage root fly with the site's other brassicas, and the same input-free defences apply -- fine mesh or fleece from sowing, and crop rotation to avoid a soil-borne pest build-up.