Clematis (Clematis spp.) is the name of a large group of evergreen and deciduous vines from the buttercup family. Clematis vines occur in a range of sizes and flower colours. The vines grow best in areas with cold winter weather. Yellowing foliage is a commonly encountered problem with clematis.
Excessive application of a potassium-rich fertiliser results in a magnesium deficiency, which in turn causes leaf yellowing.
The foliage on affected plants starts to turn yellow between the veins. Leaf yellowing in clematis frequently starts to appear early during the growing season.
To help cure leaf yellowing in clematis, incorporate Epsom salts or magnesium sulphate directly into the soil. The recommended rate of application as listed in "An Illustrated Encyclopedia of Clematis" is 28.4gr. for every 10 square feet of land.