Hostile Takeover

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Rosa mulliganii

The climbing rose Rosa mulliganii has engulfed a Douglas fir.

For many gardeners, an important principle is ‘year-round color’. We strive to ensure that there are flowers, fruits or fancy foliage to view and enjoy for twelve months of the year. At Heronswood, one of our most popular approaches is to grow flowering vines into trees and shrubs. A late-flowering clematis grown thorough a spring-flowering shrub doubles the seasonal appeal, giving much more bang for your buck. But it’s important that you take care to choose appropriate partners as some vigorous vines will smother smaller shrubs.

There are a few factors to consider when making your choice. First and most obvious, choose a vine that looks good when the tree or shrub does not. Our evergreen tree Azara microphylla flowers in spring, releasing wafts of heavenly chocolate scent. We added a summer-flowering clematis, which is barely visible when the Azara is doing its thing. Second, choose a vine whose pruning regimen is appropriate to its host. Late-flowering clematis can be pruned to ground level each year, so not only do they never overwhelm the tree, but pruning is simple. Annual or tender perennial vines work well, too, as they can be removed entirely in winter. The deep purple bells of Rhodochiton atrosanguineum form an arresting sight growing through an evergreen yew, then winter cold prevents the plant from outstaying its welcome.

The last, and perhaps most important factor is scale; choose a vine appropriate for the size of your tree. Large, vigorous vines need robust trees to hold them up. This is exemplified at Heronswood by Mulligan’s rose (Rosa mulliganii), which has already swallowed one large Douglas fir and is beginning to embrace its neighbor. Named after Brian Mulligan, former curator of the University of Washington Botanical Garden in Seattle, this botanical behemoth is in full bloom right now. Luckily, this weekend (Friday-Sunday) Heronswood will finally open its doors to the public, and it’s a great opportunity to view our many voluptuous vines in all their glory.

– Dr. Ross Bayton, Heronswood Assistant Director