My thanks also to Wim Snoeijer for a number of the photos.
This is an attractive cultivar and a suitable gift for a friend or relative with a birthday as it a strong grower and should therefore be able to survive, even if your friend or relative is not that knowledgable about clematis.
Clematis 'Zohapbi' HAPPY BIRTHDAY was one of the varieties in the Royal Horticultural Society (RHS) Late Large-flowered Clematis Trial held at Wisley, UK from 2012 to 2015. I visited the trial at Wisley several times and reported on it over three years in the Society's journal, Clematis International. In 2016 my comment on C. 'Zohapbi' HAPPY BIRTHDAY was that it was Very Good/Excellent and that it deserved an Award of Garden Merit (AGM). The RHS judges also rated it highly and it was awarded an AGM as the result of the trial.
The flower colour is interesting and challenging! I would describe it as a deep purple with a blue tinge but the colour is very difficult to photograph, especially in a garden setting in bright sunlight. When the news of the RHS AGM award appeared in the RHS magazine, "The Garden", the photo of the clematis printed was a light mauve, I suspect having been taken by a gardener, rather than a photographer, in bright sunlight. Wim Snoeijer, the breeder, sent me a photo of some flowers of C. 'Zohapbi' HAPPY BIRTHDAY lying on top of "The Garden" magazine and the flowers were unrecognisable as the same plant.
Wim Snoeijer also sent me two other photos which he confirmed were the correct colour and these are shown on this web page. Part of the problem of photographing this cultivar is that the flower colour fades as the flowers age. They are definately a purple on opening and they mature a lighter colour which is described elsewhere as cobolt blue but I think that purply blue is a more accurate description as, for me, cobalt blue is a bright blue. The photo at the top of the page shows the difference between the newly opened darker flowers and the open lighter flowers.
My husband's photos (Ken being the photographer in our family) taken on a sunny day at Wisley showed the flowers lighter and redder than Wim's photos and Wim told me that the colour on this photo was not correct. In the RHS trial two plants were grown together so I have included one photo taken by Ken to give you an idea of how the plants growing in the trial performed. The photo was taken in 2015 so the plants were 3 years old and they are about 2 m or 6 feet high, perhaps a little taller, as they covered their support.
On J. van Zoest's web site, C. 'Zohapbi' HAPPY BIRTHDAY is described as reaching 3 m high and liking a sunny place in the garden. The flowers are 6-10 cm across and are more or less upright so they face you. There are usually 6 tepals. In Europe it should flower from late June into early September. The plant should be pruned in spring to about 25 cm above soil level and it is suitable for Zone 5.
C. 'Zohapbi' HAPPY BIRTHDAY was raised by Wim Snoeijer in 1999 and selected in 2002. We don't know its parentage but this cultivar is placed by Wim in the Jackmanii group which is part of the Late Large-flowered Clematis group. It is propagated by J. van Zoest B.V., Boskoop, The Netherlands and was introduced in 2009. The plant has Plant Breeders Rights which means that unlicensed propagation is forbidden.
When the plant was introduced in 2009 it won a KVBC Bronze Medal at the Plantarium in The Netherlands. The British Clematis Society grew it for 3 years in a growing trial similar to garden conditions and awarded a Commended Certificate in 2013.
So whatever the exact flower colour, C. 'Zohapbi' HAPPY BIRTHDAY should give you or your friend or relative a lovely display in the garden!