One of my favourite gardening books is Allen Lacy’s “The Garden in Autumn.” In it he speaks of lingering perennials, those plants which are interesting over a long period of time. He writes “A garden may be transformed when the plants specific to autumn begin to bloom, but the lingerers, together with the architectural features of the garden such as pathways and walls and steps, give it a sense of unity over a longer period.” A perennial that has lingered in our garden centre for months is Penstemon mexicali ‘Red Rocks.’ Our crop began blooming in June, we sheared back the remaining plants in late July and they were back in bloom a month later. Now that it’s October the few pots that are left still have blooms lingering.
Penstemon is a large genus of annuals and perennials. Penstemon mexicali is a hybrid between Mexican and American species. It has glossy, narrow foliage, grows about 18 inches high and 15 inches wide. Tall spikes of bell-shaped rose-pink blooms with white throats form in late June. Shear back these blooms when they’re finished and the plant will quickly bloom again. ‘Red Rocks’ will tolerate drier soils and thrives in full sun. Hummingbirds find both the colour and shape of the blooms irresistible. Most penstemon are deer resistant. This hybrid is hardy to about -28 deg. C. Don’t cut back the foliage until spring and ensure that the soil is well-drained to enhance winter hardiness.
‘Red Rocks’ is an excellent perennial, as are many of the penstemon, for a sunny slope. You can see several examples of this genus growing on the south sloping Xeriscape Garden at the Summerland Ornamental Gardens. It combines beautifully with the blue flower spikes and mounding growth habit of Nepeta ‘Walker’s Low.’ Use ‘Red Rocks’ as a thriller plant in a container garden, planting blues, greys and whites as fillers and spillers.

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