Winter vegetable and herb growing

I divided some of the herb plants growing in the patio and potted them up to grow on my kitchen windowsill this winter. We'll see how they do. Years ago I attempted this for several years in a row, but each time the herbs developed insistent aphids and gnats that would not go away not matter what I did.

I also have a small experiment growing in a small section of the patio. I cleared a way maybe a three-foot patch in which I sowed a few rows of spinach seeds. I covered the area with clear heavy-duty plastic sheeting, suspended/attached between two half moon metal supports...essentially creating a coldframe. Not exactly sure how water's going to get in there, but of course the soil with the seeds in it will get moisture from surrounding soil I suppose...wicking.
If this goes well, I will consider expanding the area. Trouble is I'd have to move some perennials.