“Sport. New growth that spontaneously appears on a plant but bears no resemblance to the parent plant. Horticulturally it is an abrupt deviation or mutation. For example ‘Multi Blue’ (a double flower) is a sport of ‘The President’ (a single flower).” (Source: Simply Clematis: Clematis Made Simple)
I have had my Clematis ‘Multi Blue’ for at least 10 years now and it has always been a very dependable bloomer producing lots of spectacular sea-urchin type blossoms. However, this year is different because along with its regular crop of double flowers, it has generated two “single”, large-flowered blooms (see picture above). This manifestation happens when a clematis “sport” starts to revert back to its original parent plant. If you are new to growing clematis and came across this strange plant phenomenon of having two different flowers residing on the same plant, you might possibly be puzzled by the occurrence. However, since I know C. ‘Multi Blue’ is a sport of C. ‘The President’, I was better prepared for the possibility of it doing an about-face.
So, if you are growing: C. AVANT-GARDE (sport of C. ‘Kermesina’), C. ‘Blue Light’ (sport of C. ‘Mrs Cholmondeley’), C. CRYSTAL FOUNTAIN (sport of C. ‘H.F. Young’), C. ‘EMPRESS’ (sport of C. ‘JOSEPHINE’), C. ‘Fairydust’ (sport of C. ‘Venosa Violacea’), C. ‘Multi Blue’ (sport of C. ‘The President’), C. ‘Sprinkles’ (sport of C. ‘Prince Philip’) or C. ‘Tie Dye’ (sport of C. ‘Jackmanii’), there may be a chance (since sports do not always remain permanent) that any of these clematis will revert to its parent plant. If this “sport spectacular” should happens to you (rather your plant) I think you should take consolation in the fact that it is not the end of the world as you will still possess a clematis, only now it will be that of the original parent plant form, which are still pretty plants. Think of it as trading your plant in on a new model, but without having to go to the trouble of digging out the old one and planting a new one.
For me, the stunning C. ‘Blue Light’, C. ‘Fairydust’, C. ‘Multi Blue’ and C. ‘Tie Dye’ are well worth growing in spite of the possibility they may take you on a morphological adventure. In my case, I have truly appreciated every minute that they graciously have bestowed upon me with their altered genetic forms in my garden. I love these plants, so if they should (or should I say when they) decide to return to their roots, I have every intention of acquiring new ones. The bottom line is don’t be at odds with this oddity, embrace it, because it is one wager in life that, in my opinion, you won’t lose.