Answer: You might be able to train a weeping Blue Atlas cedar (Cedrus atlantica 'Glauca Pendula') into a pattern or at least grow it as an espalier flat against the wall, but that is the only blue evergreen I can think of that might do that for you. You could also use some of the blue and silvery toned junipers in such a grouping or perhaps some of the so-called blue hollies or spruces such as Picea pungens 'Globosa'. Among deciduous plants, possibly Salix purpurea 'Canyon Blue'; some of the white variegated plants will read as silvery blue such as the Emerald Gaiety Euonymus fortunei, or the variegated shrub dogwood such as Cornus alba "Elegantissima". Yight also look at some of the grasses including Festuca cultivars such as Festuca cinerea 'Elijah Blue' or a Panicum such as "Heavy Metal". Butterfly bushes are another possibility. Perennials offer a wide choice but certainly lavenders such as Munstead and Hidcote need to be there as do the many different types of Iris and perennial Salvias in purple and blue along with Liatris. You might also want to try Verbena bonariensis, although not reliably hardy it sometimes overwinters and usually seeds about, it has flowers and foliage perfect for your scheme. Clematis might be another possibility as it has many cultivars with blue and purple flowers. If you have a shady spot you will want to use some of the blue toned hostas along with Pulmonaria and Tricyrtis. You might find the following listing of perennials and annuals helpful as a start. You may need to cut and paste the complete url into your browser to make it work correctly.
Have fun with your project!
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