Winter greenhouse - should lettuce follow tomatoes or potato

[Sabz]

Hi guys,

It is my third time trying to post something, hope I get it right this time.

I would like advice on crop rotation. I will build a winter greenhouse to grow lettuce, spinach, etc.
I can build this on two gardens:
#1 - that had sunflower in 2014, will have tomatoes in 2015.
#2 - that had tomatoes in 2014 and will have sweet potatoes in 2015.

The challenge I have is that some of the winter crops need to be planted around 4 weeks before I finally cut down the previous crop.
I think it would be easier to sow through the sweet potatoes as they are less "bushy" than tomatoes and create less shadow.
But, the potatoes can remain in ground later in the year than tomatoes, so using the potato bed would require that I harvest the potatoes a bit earlier than I would like.

Thanks!

[FelixLeiter]

I would normally advise direct sowing in early autumn, while the soil is warm and when germination will be rapid and robust. But in this case I would advise bringing on your lettuce in pots / cell trays. By the time they are planted out, they will have advanced about 4 weeks. If you don't have room in the greenhouse for raising seedlings, raise them outside then bring them in.

[peter]

Sabz, where are you based?
From your outdoor crops it sounds like outside the UK.