Clematis and Cup Plant: A Fabulous Combination. Or Not.
So I had what I thought was a brilliant, original idea. Grow Cup Plant (Silphium perfoliatum) in front of ‘Jackman’ Clematis (Clematis jackmanii).
I love both plants. Jackman Clematis are widely esteemed for being smothered with rich purple flowers. Cup Plant, on the other hand, is not too common as a garden plant. Mainly it is grown by wildflower enthusiasts and prairie restorationists.
Almost everything about Cup Plant is big: the plant itself (up to 10′), the leaves, the enormous clumps it will form if not kept in check. The sunflower-like yellow flowers are on the small side, but they are produced in quantity. For those of you who are not part of the Big is Beautiful School of Gardening (I am a charter member), Cup Plant has other virtues. The perfoliate leaves clasp the stem to form a cup that holds rainwater, which attracts birds and insects. In addition, the seeds are addictive to goldfinches.
My Clematis grow on the west-facing wall near the garage, and they do very well if I say so myself. My idea was that they would grow through the Cup Plants. Then they would bloom at the same time, the yellow Cup Plant and purple Clematis contrasting nicely.
Sounds nice, doesn’t it? Never happened. Not gonna happen. Basically, they never bloom together. While they could in theory, they seem to react differently to variations in the weather so that any overlap in bloom time is minimal at best. In addition, the Clematis don’t seem to like climbing on the Cup Plant. All the Cup Plant does in practice is hide the blooming Clematis. In fact I get complaints from neighbors who enjoy looking at the Clematis and don’t like having their view obstructed.
I’ve thought of getting rid of the Cup Plant at this location – I have them growing in two other spots in the garden. Judy doesn’t want me to, though she also complains of the Clematis not being shown to their full glory. I’ve thinned the Cup Plant stalks, but I’m not that solves the problem.
Plants just refuse to follow directions if they don’t feel like it.
gardeninacity 
Ain’t that the truth! Go ahead, finish the job. Remove the cup plant in front of the Jackmanii.
I would but first I have to convince my Life Partner, who just doesn’t like change in general.
Ah yes, we’ve all head experiences like this. Last year, I planted Joe Pye weed in my Gettysburg garden with the idea that it’s tall pink blooms in August would echo the blooms of the tall Sedum matrona on the far side of the flower bed. It looked beautiful in my imagination — but the Eupatorium was finished blooming long before the Sedum began. Sigh.
Seems the best combinations are usually accidental. Planning puts a jinx on it.
I battled this with my hyacinths and tulips. If they don’t bloom together this year, I’ll need to fill in with other things that do.
Hmmm. Which blooms first?