Clematis vines are HUNGRY for vitamins and nutrients. Feed them a clematis smoothie for massive blooms.
Save banana peels, eggshells, and tomato discards. Put in a blender with water, purée, then pour around the root areas.
Clematis eat a lot and should be fed supplements like this from February through September.
You can also feed them coffee grounds in the same manner as you would a rose plant (See post on coffee & roses).
Clematis seems to love the same nutrients that roses love. You CAN co-plant them, and the clematis will climb the rose bush, but you’ll need to feed heavily so the clematis doesn’t starve the roses of nutrients.