Q: I have several white and purple clematis that never seem to thrive. In the spring, the vines grow up the arbor high enough to flower, but then they blacken and die back nearly to ground level. After some weeks, a bit of green will show, and the vines will again creep upward several feet before dying back again. This happens all summer. Other clematis in my neighborhood look wonderful, so I’m baffled. — Jerry Joyce, Lexington, Ky.
A: Your plants have classic symptoms of a disease, clematis wilt. Replacing the afflicted vines with new, “clean” ones of that variety or even replacing the soil won’t help. Clematis wilt is caused by a soilborne fungus, and the popular large-flowered hybrids you are growing are very vulnerable. But the smaller-flowered clematis species and their varieties are less susceptible. If you want the classic clematis look, the best alternatives are the viticella hybrids. Their flowers are between 3 and 5 inches across (depending on the selection) — about half the size of those of the large-flowered kinds — but because the viticellas produce so many of them, the flowers will be cheek to cheek on the tops of the vines, and from a few feet away the effect will be much the same as you’d get from the large-flowered varieties. Also, they’re easy to prune. Simply cut them back to 12 inches each spring. Some good choices are ‘Blue Belle,’ ‘Étoile Violette’ (both purplish), and ‘Huldine’ (white). The biggest difference with the viticella hybrids — aside from the fact that they will actually blossom wonderfully for you — is that they flower slightly later than the large-flowered clematis, in early July rather than in June. But the viticellas continue flowering profusely into autumn. If you refuse to give up on the large-flowered varieties, set the crown (where the roots meet the stem) 4 inches below the surface of the soil. This gives the dormant buds below ground level a chance to sprout and send up replacement shoots.