Colorado’s Iconic Blue Spruce

Bowman's Root and Blue Spruce_DBG_LAH_4163Colorado has a love affair with the blue spruce (Picea pungens). Perhaps we’re enamored with the striking, steel-blue tint to the needles, and the way the color causes fall’s orange leaves to glow. Perhaps we appreciate the towering, pyramidal shape of a mature tree, or the short and squat dimensions of a dwarf cultivar.

A number of gardeners I’ve talked to added a blue spruce to their yard because it’s Colorado’s state tree. Blue spruces may not be the easiest species for Front Range landscapes, but they’re definitely worth the effort.

For one thing, spruces need a fair amount of water. Yes, they’re natives. But they’re native to the higher elevations that receive twice the precipitation as do the foothills and high plains. They’re commonly found along stream banks or the bottom of canyons, where the soil is constantly damp. While they can grow on mountain slopes —spruces can be found all the way to the tree line— it’s usually a site shaded by other conifers. Supplemental water is a must; don’t plant them in a xeric section of your garden.

Picea - Spruce_FedWayWA_20090920_LAH_0762Another consideration is how big these trees get. A mature blue spruce can reach over 150 feet in height, with a spread of 25 feet or more. That’s a lot of tree for a small yard! And remember that the branches start at ground level. I’ve seen spruces that have been “limbed up” to create space underneath, but they look atrocious with their knobby trunk exposed. I want to run over and put bloomers on them! Don’t shame your spruce. If you want to walk or landscape under your tree, plant something else.

For those of us who love spruces, but don’t have an estate to accommodate them or the budget for lots of water, there is still hope. We can plant smaller cultivars. As the name suggests, ‘Fat Albert’ is a short and squat tree. Developed in the late 1970s, it grows ten to fifteen feet tall, and seven to ten feet high—much smaller than the standard species. Shaped as a perfect pyramid, it would make an excellent living Christmas tree for the front yard.

Picea pungens 'Montgomery' - Blue Spruce_XG_20090826_LAH_9731.nefIf your space requires a shrub instead of a tree, ‘Montgomery’ (left) is even smaller, typically reaching only three feet in height and width. However, some individuals throw off all restraint and grow taller than we expect, so you have to keep an eye on them!

Both of ‘Fat Albert’ and ‘Montgomery’ spruces have closely-spaced branches and needles that shine a silvery blue. Other smaller cultivars include ‘Blue Globe’ and ‘Iseli Foxtail.’

While they tolerate deer and rabbit damage, spruces are subject to a number of pests which can damage needles, disfigure branches, or even kill the plant.

Blue spruce tussock moth selectivity - scanned CSUEx-001Perhaps the worst pest in our area is the Douglas-fir Tussock Moth. In spite of its name, this insect prefers blue spruces, like the one shown here, courtesy of CSU. The larvae work downward from the top of the tree, defoliating the twigs and branches as they go. (Note the dead top on this tree.) They’re so voracious that the top of the tree may be killed in only one season. If not controlled, these hungry caterpillars will eat so many needles that the tree dies. If the top of your spruce looks as if it’s going bald, take action immediately. CSU has an excellent fact sheet with more information: Douglas-fir Tussock Moths.

Other possible pests include various spider mites, budworms, needleminers, sawflies, aphids, beetles, scale, and weevils, along with various fungal diseases, but a healthy tree has little to worry about.

Coolie gall on Picea pungens @ColoCollege 2003july6 LAH 096Sometimes spruces develop weird growths at the end of their branches. These are Cooley spruce galls, and they’re caused by a type of aphid. While some gardeners consider them unsightly and prune them off, Cooley spruce galls won’t hurt your spruce.

Perhaps the best reason to plant a blue spruce cultivar is that it isn’t yet another juniper. At least, that was my motivation!

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