Growing roquette

My friend gave me some organic roquette seed which I planted. However, the plants just grew a thin stem, a couple of very small leaves at the bottom and nothing else except a white flower! I am going to leave it and hope it will self seed with better results, but what did I do wrong?

 

I find it does much better sown in the autumn, producing leaves from Oct thru til April in an average winter.
Like you I leave some plants to self seed and find plenty of seedlings from end of Aug to Sept depending on the rain. I transplant into composted beds following early crops and find they grow away strongly and also avoid the flea beetle holes they suffer from in spring.
I also use the same self seeding technique for corn sald and land cress and haven't bought seed of them for about 7 years

 

That will be it then, I didn't treat the soil before hand and just left them to it as my friend had with hers ( we have same soil type). I will try again in the autumn.