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RHS WISLEY STEPPE – PRAIRIE 2008 –

As part of the new landscape by Tom Stuart Smith around the Bicentennial Glasshouse, I was invited to develop the last portion of space to the North West of the Glasshouse with a naturalistic plant community that would cope with the dry sandy soils of the site.  In January 2008 the 1400m² site was sown with a prairie-steppe vegetation.  The steppe species included Western North American species such as Penstemon, and European Pulsatilla and Dianthus.  The design assumption was always that the relatively short lived Penstemon species would gradually decline and the system become dominated by the larger and more long lived prairie species, and this is what has happened.  The vegetation is managed by cutting off in spring and then flash burning. Pulsatilla vulgaris has responded very well to this regime and in spring is the dominant species, but because of the fear of damaging this early flowering species, burning has been carried out in Februrary rather than in March or even April.  As a result the burning has not controlled weeds as effectively as there has been a window of many weeks in which competition post–burning from the steppe prairie species is non-existent.  This chain of unintentional events has led to prairie become weedier and more slug rich with a corresponding decline in Echinacea pallida.  In 2014 we intend to hold our nerve and burn later as the first step in recovering the Echinacea, even if we destroy the flowers of the Pulastilla.


The steppe species were almost mind-blowing in June 2009, with jewel box like combinations of colour and form

The steppe species punctuated by the paddle shaped, ultimately enormous leaves of prairie dock,
Silphium terebinthinaceum


By the following year (early June 2010) some of the Penstemon are being excluded by the closing vegetation as the take over of the prairie species begins


By July-August 2011, Echinacea pallida is one of key dominants in the community, with the white  “bobbles”  of Eryngium yuccifolium providing constrast, although this species is in decline;  the site soils are too dry for this species.  4m tall emergents of the yellow see through daisy, Silphium laciniatum  provide abundant vertical scale.


The dry, relatively open site suits species that are often difficult in British plantings, for example the orange Asclepias tuberosa.


Late October (2013) is dominated by Aster oblongifolius and A. turbinellus, two species that have done rather too well on the site and which will be dramatically thinned in winter 2013-14.


The magnificent foliage of Silphium terebinthinaceum turns copper and rust in late October as the asters reach their peak