There is not much actively growing at this time of year, but it has been a mild winter so some cold-tolerant plants are making good growth.
Autumn sown peas have survived and thrived in large Air-Pot containers. Sweet Peas can do well over winter as well as hardy culinary varieties, if given some protection. My pot full of Meteor is about 30cm tall now and has just produced its first flower. A January sowing has just been made in gentle warmth and will go into an unheated greenhouse once germinated. These pot grown peas should give a succession of pickings. Later sowings can be the more tender second early and maincrop varieties and particularly productive are the sugar snap and mangetout types which have edible pods.
The mild winter has benefited plants which sometimes look very bedraggled after harsh weather. Evergreen ferns such as the Japanese Tassel Fern still has fresh-looking lustrous dark green fronds. Also exotics such as Agave filifera from Mexico are looking fairly unscathed by the dark days of winter.
An Air-Pot container thinly sown now with leek seed should quickly produce little grass-like plants. These do better in a potful of clean well drained potting compost than sown directly in a seed bed, where they can easily be overwhelmed by weeds. These plants should go on to become pencil thickness transplants by mid-summer and full grown leeks a year from now.
If you can provide some heat and light it is not too soon to be sowing a few tender crops such as aubergine and hotter chillies like Scotch Bonnet which need a really early start if they are to crop well before the end of summer. But it is easy to get carried away and end up surrounded by an indoor jungle of overgrown tomatoes and cucumbers by late Spring. On balance with faster growing plants I favour holding back and delaying sowings.