Clematis are happiest when their roots are kept cool and moist, so try to plant them where that the base of the plants will be lightly shaded by other, lower-growing species. Otherwise, use a clematis root protector, or top-dress the rootball (avoiding the immediate crown), with a generous layer of shingle or pebbles. In early spring cut back the previous year's stems to a pair of strong buds about 15-20cm (6-8in) above ground-level and apply a slow-release balanced fertiliser and a mulch of well-rotted garden compost around the plant - again avoiding the immediate crown.