could be down to the mineral availability in the soil and the water retention of the soil. greenhouses tend to be better managed, well in my case it is I water that regularly where as the soil outside rarely gets watered unless it has been dry for a long time.

Thanks S, but I give them plenty of water regularly. I guess I'll just have to make extra room in the greenhouse next year. I can't see them doing any better in containers outside.

Hi S, I grow them in my greenhouse because they won't ever grow in my raised beds. But now I have your info maybe they will next year. My topsoil grows spuds, onions and peas o.k. , so is not too bad, but never beetroot.
Compost it is next year thanks.