Swede is just a stem

You might have to go into more detail about your growing methods and your local weather.

I have had mixed results with swede but have grown them successfully here in the south of England.  I would sow in May into modules, grow them on into sturdy little plants, then plant out and keep well fertilised and watered over the summer.  They do tend to be trickier than cabbage and more prone to failure if the weather is a bit erratic e.g. hot dry spells in spring, droughts over summer and so on.