greenhouse in winter

Hi Wesley, welcome to GOY.
Many vegetables can be grown in a cold greenhouse, with the aid of thin polythene sheets. Lettuce in deep trays made of pallet wood. Radishes in normal plastic seed trays. Potatoes and carrots in large deep pots. Start cabbage and cauliflowers for planting outside later. Cover with bubble wrap when it is frosty. Do not over water.

You will have to get them well started before winter and don't water too much unless they are dry. Water in the morning if possible so they do not sit in cold compost overnight. Salad leaves are successful also coriander ,parsley, sage but not basil unless it's warmer. I start climbing French beans (or you could do dwarf) in a large pot and you get a few beans quite early on. Don't expect too much to produce, but it is nice to be able to pick something early.

I usually grow 'oriental' salad/stirfry greens, (komatsuna, mibuna, mizuna, pak choi) and rocket. I started some off in the autumn and am still harvesting leaves by cutting some and leaving the younger ones. Also started some off as late as December and although they have survived even when the top of the GH was covered in frost, they have been very slow growing in comparison so I probably wouldn't sow those as late again. I once started off some broad beans in the autumn in there but they got a bit leggy so I do those outside now.