I think any of those listed would work fine. Here, the native species C. ligusticifolia or virginiana (depending on which of the country one resides) grow in exactly the manner you describe - no attention, a fair amount of shade and clambering up into and over anything in their path. If not excessively invasive in your area, Clematis vitalba is another possible candidate.

I grow some clematis on trellises, many on shrubs, and a few just rambling. Of the ones I grow, I think Betty Corning would be fine scrambling across the ground or up a large shrub. Mrs. Robert Brydon (C. heracleifolia var. davidiana x C. virginiana, but also listed as C. x jouiniana) scrambles across the ground for me and is quite large and vigorous. While both of these are hybrids, both are easy- to no-care, type 3, and compete well with other plants. C. virginiana grows wild here where it scrambles up large shrubs and trees including in areas that are totally unmanaged.

Hi Campanula,

I grow Fargessii in full shade (building shade). From a 10 inch plant it has morphed into a 12' X 12' monster in 3 years only. It is the longest flowering clematis in my neck of the woods, approx. for 2 months. It flowers in stages, so you'll have a cluster of flowers, here and there.

You can also consider planting one of my favourites, triternata 'rubromarginata'. Not a species, mind you. Mine, flowers with less than 3 hours of direct sunlight. The plus with this clematis is the lovely almond fragrance of the flowers that wafts unexpectedly now and then...

I'm sure you can plant any from the Tangutica group also. Mine has grown into a monster that scrambles all over the place. Apparently Clematis serratifolia (same group) has a citrus scent, if you are fragrance inclined.

Good Luck :-)

cheers, True-Blue, I had quite forgotten about the tanguticas and now I am thinking of yellows, I might have a stab at rehederiana again. I grew one from seed a few years ago but it completely overwhelmed my tiny garden....but maybe scrambling about on one of the sunnier banks. Definitely keen on Fargesii.

Yes, the tanguticas could be kind of giant. They will scramble over anything in order to get to sun. What I like about it (I have the Golden Harvest cultivar) is the fine tender green leaves. Very dainty.
In comparaison Fargesii's leaves are rather coarse.
The good thing is you can chop them off, otherwise they'll develop those thick woody stems...