When the weather is hot, we look to cool blues for relief. We've written about blues in autumn, when they contrast strikingly with the fiery colors of the changing foliage, but in summer, especially late summer when we are tired of the heat, we like a splash of blue almost anywhere. The palm pictured above is hardy to about 10 degrees fahrenheit, so it is not a tropical. It's short and clump-forming, so easy to mix with other kinds of plants.
Blue repeats through the border from the Picea pungens to the Chamaerops to the Brahea at the far end.
There are lots of blue palms, many of which are cold-hardy. For a bigger plant with specimen status, try the Mexican Brahea armata.
Palms provide a very different texture and structure than other plants. Because we think of them as tropical, we hesitate to mix them with temperate species. But many palms are also temperate and grow happily among conifers and succulents in their native ranges.
This silvery blue Puya
There are lots of succulents and succulent-like plants in shades of blue. You can also add blue with pots or other ceramics.
Many rocks have blue tones and can help keep the apparent temperature down. In this garden in Roseville, Oregon, the stonework gets outdone by the spruce, though!
There are many blue conifers, beginning with Colorado blue spruce (Picea pungens). There is probably not a more maligned suburban landscape tree, due to the enormous size the species attains. Happily, there are many cultivars that are slow-growing and garden-friendly. In the shot above the spruce cools down the entire garden.
The blue comes from waxes that the plant carries outside its leaf cuticles, which retard absorption of certain wavelengths of light.
For those that can grow it (it's tender), Podocarpus Icee Blue is the ultimate summer cooler. A blade-leaved conifer (instead of needles), it works with a multitude of shrubs to bring down the hot summer temps.
So plant blue to cool down your summer and heat up your fall!