I am having trouble with one of my clematis. It is six years old and both last year and this year it did not bloom. This plant receives the same care as all my other clematis.
Too much shade, excess nitrogen and improper pruning can prevent clematis from blooming. Evaluate the light conditions and look for any changes in the area. A new structure may have been installed or a tree grown and is now casting shade on this plant. You may need to move the plant to a sunnier location. Avoid high nitrogen fertilizers. A low nitrogen slow release fertilizer will provide the plant with needed nutrients without interfering with flowering. Have a soil test before using a blossom booster or other high phosphorous fertilizer. Most garden soils have high to excessive levels of phosphorous and potassium. Now evaluate your pruning techniques. Early blooming clematis species and cultivars bloom on old wood. These must be pruned after flowering. The summer and fall bloomers can be pruned during the dormant season, preferably late winter. Double-check flowering time and pruning practices.