This Clematis was raised by Wim Snoeijer at J. van Zoest Nursery in Boscoop, Holland, in 2000 and was introduced in 2008. In our garden in Cambridge, England, it grows through a Hypericum, possibly 'Red Robin', against an east facing fence so gets no direct sun until the afternoon. It manages to reach the height of the Hypericum - 4 feet (1.200m) - and starts to flower after the shrub has finished flowering and when it is in berry. C. 'Zoeastri' EAST RIVER seems to have integrifolia in its breeding and does not seem to cling to its host but has strong stems which allows it to grow through it without the need to entwine.
The flowers are 3 to 5 inches diameter (80 to 120 mm), outward facing to slightly nodding, initially bell shaped progressing to almost fully open flowers.
Recently Fiona Woolfenden sent me an image of a semi-double flower in her garden, but I have not observed this in the 4 years that the plant has been in our garden.
Colour is described as pink or light purple, but when photographing this plant the colour seems to vary according to light conditions and age of the flower. The RHS Colour Chart shows this as being Purple Violet N82C with the central bar on the reverse of the sepals being Purple N78A.
This week, mid July, we visited Sheila Chapman's garden in Chelmsford Essex only to find C. 'Zoeastri' EAST RIVER growing up an obelisk which enabled me to get a full size image of the plant. I prefer to see clematis growing through shrubs generally as they can enhance them when their peak of interest has waned. The plant in our garden is now starting into bloom (mid July) with only one flower fully open and two others just opening.
C. 'Zoeastri' EAST RIVER in Sheila Chapman's garden
C. 'Zoeastri' EAST RIVER growing on its own or through a shrub can be enhanced by combining it with other Clematis which is the case in our garden where C. 'Semu' and C. 'Zostarri' STAR RIVER flower, sometimes all together but there is also the chance that the flowering period will be lengthened by a careful choice of plants.
I recall that a few years ago this plant was being offered as a cut flower under the name Amazing® London, but I have no knowledge if this took off commercially.
Editor's note: According to their website, Marginpar of the Netherlands still market Clematis Amazing® Star River in their Clematis Amazing® series of cut flower clematis.