Rooftop trumpet vines?

Dear Expert (Carrie, Bob or Susan)
We have a client who’s property is situated on the 16th floor with a rooftop garden in downtown Seattle. The terraced garden faces south and southeast. The 4 trumpet vines are each in their own containers that are 24″ square x 26″ deep along with Algerian Ivy, trailing Rosemary. They get full sun and some wind, but are up against a wall. The foliage growth appears normal and they’re working their way up the metal trellis support. They have not bloomed yet, nor do they seem to be developing any buds. They bloomed last year (their 1st year in that spot) just coming out of a #5 nursery pot. So I can’t imagine that it’s because they’re growing in containers now. The pruning I did this spring was very light so I can’t see how that may be to blame. I also fertilized them in spring with an organic 9-3-4 all purpose fertilizer. I can’t figure out why they haven’t bloomed and hope you can.

Dear Cheryl,

Thank you for your question on trumpet vines, (Capsis radicans).  An American native, this vine really likes warm weather and with the exception of several days we really didn’t even have summer this year.  Also, some say it takes several years for the trumpet vine to flower but since it flowered last year this is probably not the problem.

This size of your container sounds fine, and your pruning technique was probably okay. The trumpet vine blooms on new wood, but it’s best not to cut it back too severely in the winter.

We’d recommend fertilizing your container plants more often, at least every two weeks if not weekly.  Miracle Grow would be an easy product to use.

Let us know how this works (next year).

Susan, Bob, and Carrie

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