Blue Spruce (Picea pungens)

About Blue Spruce

The needles of the Colorado blue spruce have a slight blue-green tint

Our state tree can be found growing in the drainages and along streams, creeks, and rivers in riparian settings. Mature blue spruce in the Colorado Front Range will be found as tall as 75 feet tall and 30 feet wide, although they tend to be a little smaller when planted in your yard.

Even though it is known for its drought tolerance in other parts of the country, in our area blue spruce has the highest water requirement of the native conifers. Like all spruce, it prefers consistently moist soil.

Blue spruce trees also tend to grow best in more acidic soils with lots of organic matter and depth, and are often found near areas where water runoff accumulates. Because of this soil environment, spruce can be damaged by contaminated soils and groundwater before other trees, acting as a “canary in the coal mine.” This situation is prevalent near failing leach fields and roadway drainages where salt builds up in the soil.

If you plant a blue spruce seedling, be aware that the roots will only reach down about 2 ½ inches during the first year, making it more susceptible to freezing during the winter months.

Plant blue spruce in an area with well-draining soil, as water pooling can lead to rotting roots.

Pests & Diseases To Watch For

The most common blue spruce pests in the landscape are two insects that do mostly aesthetic damage; the Cooley spruce gall and white pine weevil. Both leave the tree looking less than desirable in our outdoor living areas but generally don’t significantly affect the overall health of the tree. Other pests and diseases are less common but can cause more damage.

Cooley Spruce Gall

Cooley spruce gall is caused by a small insect called an adelgid (or wooly aphid). This bug is very similar to an aphid and spends about half its life on spruce (the rest of the time, it infests Douglas fir).

The Cooley spruce gall looks a little like a 2- to 4-inch long prickly cucumber. It’s usually found on new growth at the end of spruce tree branches where it starts out a light green color in late spring and early summer, and then dries out and turns brown in July.

But while they may look alarming, Cooley spruce galls actually do little or no damage to the tree. In most cases, old galls are covered by new growth the following season and become almost unnoticeable within a few years. There’s no need to remove the galls.

See our Cooley Spruce Gall Adelgid page for more information.

White Pine Weevil

The white pine weevil causes the dominant leader (the very top of the tree trunk) to die back. This damage, known as a shepherds’ crook, will occur annually to the tree unless the weevils are controlled. Over time, white pine weevil damage leaves the plant looking more like a shrub than a tree.

Both of these pests are treated in spring and late summer/early fall.

Spruce Bark Beetle

Blue spruce is also attacked by a bark beetle, similar to the pine beetle, that can cause extensive damage to the tree. It is treated with the same methods as pine beetles (spraying and pheromone packets), although treatments are applied slightly earlier in the season.

Spruce bark beetle problems can be harder to get ahead of because diagnosis is more difficult. This difficulty is made worse by the spruce’s dense lower limbs, which obscure the view of the tree base. In many cases, once spruce trees begin to die and needles are turning color, the insect has already moved onto another tree.

Ips Beetle

Ips beetles also damage spruce, usually attacking stressed trees (much like they do with pine trees). That means recently-transplanted trees are also susceptible until they’re well-established, as are trees that are stressed by disease, drought, or other insect pests.

Treatment for Ips beetles occurs in late winter/early spring before temperatures warm up and the insects become active. Depending on weather conditions, treatment can happen as early as February or as late as April. Timing of Ips beetle treatment is the same regardless of the host tree.

See our Ips Beetle page for more details.

Pine Needle Scale

We’ve recently seen many spruce trees getting attacked by a scale insect called pine needle scale. This appears as small white dots on the interior needles of the tree. As the scale feeds, it causes the tree to drop its interior needles, making it look thin through the middle of the tree.

Treatments for scale should be done in April and early May, depending on the season’s temperatures.

You can find more information about the striped pine scale on our Scale Insects page.

Fungal Diseases

In rare cases, blue spruce will also have problems with fungal diseases. The most common of these is spruce broom rust. It’s often confused with dwarf mistletoe but it’s actually a rust fungus that uses two plants (spruce and kinnikinnick, usually) to complete its life cycle.

Treatment for spruce broom rust consists of pruning to remove the affected portions of the tree. This is done during the cold months when the tree is dormant and not actively growing.

Fun Facts About Blue Spruce

Blue spruce is the state tree of Colorado and is often referred to as the “Colorado blue spruce,” but also goes by the names green spruce, white spruce, and Colorado spruce.

Blues spruce trees are a popular Christmas tree option and their boughs can be used in wreaths and garlands.

Blue spruce trees are deer-resistant, so they are often planted on the edge of a property to discourage deer from entering.

You can buy one in a container to use as a live Christmas tree and then plant it afterward. Dig the hole before the ground freezes and store the soil in a warmer location (like a garage) so it’s easier to fill the hole when you plant the tree after the holidays.

Pungens means “sharply pointed,” referring to the blue spruce’s needles.