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Using the palette of colours, textures & shapes that is available for the late summer perennial border is one of the enduring pleasures of planting design. Similarly, blending colour & form to create a seasonal mixture of highlights is one of the great challenges, taxing even the most inspiring designers.
Given that the nature of the perennial border is to grow, one of the most demanding aspects of design is to fill the rear sections of the bed with perennials that will achieve sufficient height to display their charms to the full, over the heads of their stockier compatriots. There is a select band of perennials to fulfil this role, some of which can reach three metres in height in one growing season. They can provide a backdrop for early & mid season perennials in the front of the border & then wave their flags as brightly as any other as summer blends seamlessly into a golden autumn. For some of these perennials, winter is merely an opportunity to extend their influence on the border, providing structure & form until the early spring bulbs push through. It may come as no surprise to know that some of the larger perennial grasses are perfect to create a highlight in the rear of the border. Miscanthus x giganteus climbs to 9ft or more in my Surrey garden by September, & as it is virtually indistinguishable from Miscanthus floridulus I would recommend both. Flowering varieties such as M. sinensis ‘Grosse Föntane’ & M. saccariflorus will throw tall plumes of feathery fronds, but will fall short of the formers height by a foot or so. German plantsman Karl Foerster bred grasses to grow tall & straight, so you should take a good look at those cultivars bearing his name. Molinia caerulea subsp. arundinacea 'Karl Foerster' & Calamagrostis × acutiflora 'Karl Foerster' are the ones to keep an eye out for. None of these grasses need staking – a large bonus for the work-shy gardener. Macleyea cordata is a 7ft tall, large leaved perennial that is topped with tiny peach florets. Orangey stems & glaucus leaves create an unusual backdrop for a border, but care should be taken, as it can be invasive if left to spread as it wishes. Again, no staking is needed. Helianthus salicifolius is a type of sunflower that has very fine leaves & small yellow flowers. Best viewed from a distance it makes a superb focal point to a long vista but it comes with the caveat that staking is required from quite early on. Similarly Rudbeckia ‘Herbstonne’ & R. maxima offer yellow daisy like flowers with more conventional leaves & much the same inebriate habit. Helenium ‘Goldshrauch’ is slightly smaller but will stand on its own stem with no support. In boggy conditions the fabulously named Eupatorium purpureum subsp. maculatum 'Atropurpureum' stands upright to 7ft & produces rich red umbels (a flower head shaped like un umbrella) Canna lilies are one of the most exotic plants available in the designers’ palette & they offer many different flower colours & leaf markings. Of the taller varieties, Canna musifolia is one of the more impressive. Literally ‘banana-leaved’ this species will send out leaves to a length of around 4 to 5 ft. Other Cannas like ‘Wyoming’ have copper leaves whilst ‘Striata’ has yellow & green stripes. Previously it was thought that Cannas were unable to over winter in Britain, but many people leave at least half of their plants out, as they will probably survive 9 out of 10 years in well-drained, mulched soil. |
