The late large-flowered clematis trial at Wisley provides a real wow factor from mid-summer until the autumn frosts. And for the last year of the trial, we are displaying these plants in a more naturalistic way by using birch obelisks as supports for them to climb up (rather than the less aesthetically pleasing bamboo cane and wire mesh system used previously).
Birch saplings at least 2.5m (8ft) high and about 5cm (2in) in diameter were used to create these obelisks. Three foundation holes were made in a triangular formation around each clematis and the birch supports placed in the ground to a good depth to prevent them toppling over when the plants are in full leaf. They have survived the recent strong winds, so this plan seems to be working so far!
Three birch stems are used per plant - their sharpened ends are driven by hand into holes and firmed in. The fun weaving process now begins. Branches from each adjacent support are woven together.
Young birch trees are used, as their pliable wood is less likely to snap. This process creates the struts that the clematis climb up. Working from bottom to top, each layer of supports is created, gradually transforming the birch saplings into unique works of art. Lastly, the dome effect at the top is made by bending young growth from each support into a curve and then interweaving the three supports.
The ongoing construction process has resulted in much interest from garden visitors, with some even helping briefly with the weaving. These structures have brought an amazing architectural feature to the trials field and will complement the plants as they flower later this year.
More from the RHS
See a full list of plants in the current clematis trial.
10 Award of Garden Merit (AGM) winning clematis
RHS advice: Clematis
Find out more about RHS Plant Trials