Answer: The most common reason for lack of bloom on a trumpet vine (Campsis radicans) is probably lack of sun and/or pruning at the wrong time and/or overfertilizing. This plant needs a warm location with full sun all day long to bloom its best. The north side is definitely too shady, the east side might work if it is in full direct sun all morning including the hour of noon but with a half day situation the west side would be better since the afternoon sun is much more intense. Trumpet vines bloom on new growth of the season, so avoid pruning during once it has come into active growth for the season. An oversupply of nitrogen can cause excess foliage growth at the expense of blooms, so make sure you are not feeding it too much especially if is it growing along a lawn that is fertilized regularly.
Clematis can fail to bloom for a variety of reasons, but most new plants do take a few years to settle in and perform well. Three years seems pretty typical for clematis. An eastern exposure or sun all day would be fine for this vine; it likes its head in the sun and its feet in a cool, evenly moist yet well drained soil. Some clematis bloom on old growth from the year before, some bloom on new growth of the current year, and some are able to bloom on both. So pruning can sometimes help or hinder flowering but this depends on which specific cultivar you are growing.
I hope this helps.
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