I believe that fern need well draining soil.
So,
Vinca minor comes to mind.
It is a ground cover vine, flowers in spring and can be invasive.
Not sure about conditions and availability in Portugal.

Deb

That is actually a great idea - and although I had never seen it around, it seems Vinca minor is actually native to Portugal so it should not be hard to find. If it grows well I might even adopt it as my new groundcover - since the current groundcover is the semi-invasive Erigeron karvinskianus (although it does fare great as a groundcover), which I had been willing to replace for some time now.

Thank you for your help.

I've quite enjoyed a patch of golden creeping Jenny, or Lysimachia nummelaria 'Aurea', in a dark, boggy corner near my fence. It's really bright, which might look nice with the white wall.

Another plant that might serve is one I use as a hanging basket plant in central Ohio, but is apparently popular as a groundcover farther south -- Tradescantia spathacea. Moses-in-a-basket, boat lily, oyster plant are some of the common names.

Mine is a dark purple with lavendar stripes, and I take cuttings every fall to plant it out in the summer, because I have trouble keeping it watered enough all summer here.

Good luck -- it sounds like a very tricky spot!

You could try Syngonium, they don't need much light at all. Schefflera is another option, it's often grown successfully in pots indoors so should do very well in the circumstances you describle.

A picture would help though.

I have actually found Vinca Minor growing in a neighbour's garden, so I will take some cuttings and try to grow it. If it does not like the spot, then I will try some of the other suggestions!

You can try out with some other plants too. If you store it in your parking space then it will minimise the space it utilises for the usage. You candiscard or remove any items that are not necessary and give yourself space to organise
the things.