For a tree that is native to the upper elevations of the Rocky Mountains, blue spruce, Picea pungens, does surprisingly well here. It only wants to be watered a bit through summer to compensate for the lack of rain and humidity in chaparral climates. It does not seem to miss a more pronounced chill through winter. Disease and insect infestation are uncommonly noticeable or damaging.
Garden varieties are impressively variable. Some are like big shrubbery that stays below downstairs eaves. The biggest do not get much taller than thirty feet, and take many years to get so tall. Most but not all are stoutly conical. Color is variable as well, ranging from grayish green to silvery bluish green. The evergreen foliage is very dense. Individual needles are only about an inch long.
Blue spruce demands patience, planning and room to grow. Pruning for containment compromises their naturally appealing conical form. Therefore, even compact cultivars that do not need much space will need enough to mature completely. However, because they grow somewhat slowly, blue spruce may take a few years to actually occupy much of their space, and function as intended.
Agaves are innately tough and undemanding. The main reason that they are not more popular in home gardens is that they are outfitted with nasty foliar spines. The worst of these spines are the distal tips of the large succulent leaves. Most agaves are also armed with shorter recurved spines on the margins of their leaves. Gardening with such well armed perennials can be dangerous.
A complete lack of foliar spines is what makes Agave attenuata such a deviant. The relatively pliable foliage forms big grayish rosettes that can get as broad and tall as four feet. Groups of these rosettes can slowly cover quite a bit of area. The plump stems below may eventually become exposed as they shed old foliage, but are they usually obscured as newer rosettes develop and grow.
The cultural preferences of Agave attenuata are also somewhat unusual. Unlike other agaves, it wants occasional watering and a slight bit of shade. If too exposed, it can get frosted in winter, or roasted in summer. Agave attenuata is also known as foxtail, lion’s tail or swan’s neck agave because its fluffy yellowish flower stalks curve downward, and maybe up again, to about six feet tall.
No, it is not an oxymoron. ‘Yellowwood’ is the common name for a few specie of Podocarpus. The evergreen (or ‘everblue’) foliage of ‘Icee Blue’ yellowwood, Podocarpus elongatus ‘Monmal’, really is as silvery grayish blue as the name implies. It can be as striking as some cultivars of Colorado blue spruce. It grows slowly in narrow columnar form to only about fifteen or twenty feet tall.
The finely textured evergreen foliage is ideal for both formal hedges and informal screens, although it takes a while to fill in, particularly for larger hedges and screens. Tip pruning of lanky growth of informal screens improves density. The narrow leaves are about two inches long. Fresh new foliage may be lighter and very slightly greener, which can contrast nicely with more mature foliage.
‘Icee Blue’ yellowwood will tolerate a bit of partial shade, but exhibits the best color in full sun. It prefers to be watered somewhat regularly while getting established. As it matures, it becomes less reliant on watering. Like many other Podocarpus, it is susceptible to infestation by scale insects and the ants that cultivate them. Scale produce sticky honeydew which blackens with sooty mold.
To avoid confusion with dwarf fescue blue turf grass, Festuca ovina glauca is more familiarly known as blue festuca. If planted close together and left to spread as a small scale ground cover, it is much lumpier and mounding than uniformly spreading turf. It is a clumping perennial that is more popularly grown as distinct tufts of finely textured blue gray foliage that looks like gray sea urchins.
Either individually, or in small herds, these resilient gray sea urchins mix nicely with brightly colored flowering annuals. They do not need too much water, but can tolerate as much as annuals want. Their color is best in full sun. Partially shaded plants are greener, with longer and more pliable leaves. So are feral plants that rarely grow from seed. Modern cultivars are bluer than classic types.
The evergreen foliage does not get much higher than half a foot, with thin and less impressive floral spikes that stand a bit higher in summer. It slowly spreads wider, but before it gets a foot wide, it will probably be going bald in the middle. Overgrown or balding plants can be dug and divided into new smaller plants in winter. Old foliage that gets shorn in the process is replaced in spring.
It is no coincidence that many plants with gray foliage are from mountains or deserts. Gray foliage is ‘glaucous’, which, like glaucoma, diffuses light. This helps to protect it from desiccation and scald when sunny weather is also hot, windy or arid. The glaucous foliage of Rocky Mountain juniper, Juniperus scopulorum, is what distinguishes it most from related North American junipers.
Garden varieties of Rocky Mountain juniper are even grayer than wild plants. Some are even silvery. Also, they tend to maintain a somewhat symmetrical form. Most are compact, with dense evergreen foliage. Some loosen up with age. All want full sun, and seem to enjoy warmth. They lean away from shade. Color seems to be better if plants get watered occasionally through summer.
‘Skyrocket’ is very narrow while young, like a small silvery Italian cypress that gets only about fifteen feet tall. ‘Blue Arrow’ is similar, and becoming more popular because it is more resistant to disease. ‘Medora’ and ‘Cologreen’ are more bluish green. All get plump with age. ‘Wichita Blue’ and ‘Moonglow’ are more conical. ‘Wichita Blue’ is more bluish. ‘Moonglow’ is more silvery gray.