Answer: To be honest I am not specifically familiar with a spooneri clematis and could not locate it in my usual quick reference books. However it is common for clematis to take a few years to settle in so this may be what yours is doing. The old adage of "first year they sleep, second year they creep, third year they leap" has certainly proved true in my garden time and time again, so it may be that your plant is simply still establishing itself.
Pruning practices can also affect flowering, with some varieties blooming only on old wood and some blooming only on new wood and some blooming first on old wood in the spring and again later on the current season's growth. If you have been pruning it may have been counterproductive. Fertility can also play a role in blooming; an overabundance of nitrogen can cause excessive foliage and reduced blooming but I don't think it would stop the blooming altogether. You might try giving your clematis an early spring feeding with a balanced granular fertilizer according to the package instructions followed by a light feeding again in late spring. This combined with an occasional top dressing of compost should supply sufficient nutrients assuming your soil is of at least average fertility. Finally, water can be very important in encouraging this plant to bloom. Be sure it receives that "inch of water a week" so that the roots stay evenly moist but are not soggy.
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