How to Fertilize ground clematis?
Balanced clematis feed monthly in spring, higher potash before bloom

ground clematis · Clematis recta
Plant in a moisture-retentive, well-drained soil. Keep the base of the plant and roots cool and shaded by other plants or a layer of pebbles or flat stones at the base. Plant with the crown of the clematis at soil level. Mulch in late winter with garden compost or well-rotted manure, avoiding the immediate crown. Ideal for a border where it can be supported by other plants. See clematis cultivation for more advice
Balanced clematis feed monthly in spring, higher potash before bloom