Swedes like 'heavy ground' ie. clay soil, so if you don't have that, you have to try & mimic it. You can sow seeds into module/cell trays of compost, really firm down the compost, dib a small hole & sow 2 seeds, firm the compost down on top. Keep damp until seeds germinate, then thin out the weakest seedling. Transplant the seedlings into their growing position when they have a set of true leaves - if sandy soil, really tread the soil before & after planting, if loam or clay, firm the plants in by treading after planting.
Keep them watered in dry spells - a good soaking once a week.

The plants can be susceptible to other brassica problems such as cabbage white caterpillars, flea beetle (if the ground is too dry), club-root, etc.

I've grown Best of All & Marian and they both did fine.

__________________
Sarah

“Tell me one last thing,” said Harry. “Is this real? Or has this been happening inside my head?”
“Of course it is happening inside your head, Harry, but why on earth should that mean that it is not real?”