I grew a fine crop of Purple Vienna Kohl rabi last year outside in a raised bed. I followed the instructions on the packet for growing outside so did not plant out but thinned out the plants as they get quite big and need a lot of room. A very useful and delicious veg. You eat the greens like spinach and the swollen stem like turnip, great in stews and raw in salads alike!
I too direct sow my kohlrabi with good results. A big problem is dry soil, they really do not like going dry at the roots so moisture retentive soil and possibly a mulch, (I use grass clippings, but don't if you use chemicals on your lawn.)
Lastly, I sow little and often as they are much nicer when small.
I plant gives one stem corm which is what you don't want to let get bigger than a tennis ball in cade it goes stringy. I found they kept well. Good advice from Tootsietim about sowing little and often. I was making loads of stews and soups and freezing them for the winter. It was a very popular veg. in Victorian times in this country and still a staple in Eastern European countries where they have it three or four times a week like we have potatoes.
No, it grews above the soil on the stem. The stem just swells as the plant grows! It is fascinating to watch. You are not at all dim. Dim people don't ask.
This shows it quite well
I start in modules and plant out like all brassicas at the 5-leaf stage. They are one of the most reliable crops on my clay soil.. as long as I remember to net them before the flyling rats (wood pigeons) get them! Purple vienna here, too - later sowings often last into the winter without going too woody.
Don't forget when thinning out to put the leavef the thinnings in your salad bowl - delicious.