Picea pungens
The striking color of the Colorado blue spruce (Picea pungens) is instantly recognizable. If you see a silvery-blue to blue spruce in a landscape, it’s almost certainly a Colorado blue.
There are some silvery evergreen species out there, but almost none of them have the true blue hue of a water spruce, as it’s sometimes called.
Here’s a fun fact for your trivia folder: the color comes from a waxy coating on the needles, not from the pigment in needles themselves.
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As the name “Colorado” suggests, this coniferous species is native to western parts of North America including Arizona, Colorado, Idaho, New Mexico, Utah, and Wyoming.
It also happens to be one of the most drought-tolerant types of spruce out there, which should come as no surprise given that it grows wild in some extremely dry areas.
But this adaptable species can also thrive in moist environments and anything in between. It’s versatile, low-maintenance, and distinct.
Ready to learn more about this fantastic conifer? Great! Here’s what we are going to go over to help you make the most of your blue spruce:
What You’ll Learn
Spruce trees can be identified by their four-sided needles that grow on short pegs that encircle the stem.
On Colorado blue, the needles are very sharp with a colorless tip, and they are held individually on tan to rust-colored pegs.
As the name suggests, the needles are often blue, but not always. We’ll talk about why the needles might look green in a bit.
Each of the four needle surfaces have a stomatal line, which you can see if you look closely. It just looks like a pale stripe running lengthwise.
The female cones, which produce seeds, are conical and can grow up to 10 inches long. When young, they may appear pink, green, or purple, fading to a buff hue as they mature.
These cones have thin, papery scales, which sets them apart from most other common garden spruces, except Sitka (P. sitchensis) and Engelmann (P. engelmannii). Most other spruce species have thicker, more rigid scales.
Seed dispersal occurs in the fall when the cone scales open to release seeds.
However, cones don’t begin producing seeds until the tree reaches reproductive maturity at about 20 years of age.
Male cones, known as strobili, are typically pink and turn yellow when they release pollen in the spring. They’re much smaller than female cones, usually just an inch or two long.
A mature tree can release a significant amount of pollen, which might not be ideal next to patios or entryways unless you don’t mind sweeping frequently during the season.
The bark of mature trees is a silvery gray and somewhat flaky, adding attractive texture to the garden. If the tree is growing in low-light conditions, the bark may show a rust-colored undertone.
Growth tends to be dense, with lots of branches and twigs covered in needles.
These trees can reach a towering 160 feet tall and about 50 feet wide in the wild, though they rarely exceed half that size in home gardens.
Many cultivated varieties are smaller, topping out at around 60 feet tall and 20 feet wide. Dwarf cultivars may grow just a few feet tall and wide.
Mature trees typically have a narrow, pyramidal shape, though some cultivars vary.
This tough, adaptable tree thrives in USDA Hardiness Zones 3 to 8, provided the soil is well-draining and the climate isn’t overly hot and humid, sorry, gardeners in the southern states.
Quick Look
Common name(s): Colorado blue, blue spruce, Colorado spruce, silver, water, white spruce
Plant type: Evergreen conifer
Hardiness (USDA Zone): 3-8
Native to: Western North America
Bloom time / season: Evergreen
Exposure: Full sun to light shade
Soil type: Loamy, moist, well-draining
Soil pH: 5.5-7.5, slightly acidic to neutral
Time to maturity: 20 years
Mature size: 50 ft wide x up to 160 ft high (depending on cultivar)
Best uses: Specimen planting, windbreaks, privacy screens, Christmas tree
Taxonomy
Order: Pinales
Family: Pinaceae
Genus: Picea
Species: Pungens
In the wild, some trees lack the blue color and are more of a drab green. Those with the blue hue are grouped into the variety P. pungens var. glauca.
These color differences tend to occur in clusters, suggesting a genetic basis rather than environmental causes.
A glauca variety can also turn green. We’ll talk about why that happens and how to fix it.
New growth emerges as a lighter, silvery shade in spring before maturing to the familiar blue tone.
This tree was never widely harvested for its wood, since it tends to be brittle and full of knots, Colorado blue spruce is extremely popular as a landscape ornamental and Christmas tree.
Huge plantations in the northeast and northwest supply the Christmas tree market each year.
So, ready to plant and grow your own? Let’s talk about how to do that.
How to Grow
When you’re choosing a spot for blue spruce in your garden, make sure it’s somewhere out of the way.
The needles are stiff and sharp, and you don’t want to be stepping on fallen foliage or brushing up against the branches, believe me, they hurt!
There’s a reason that the Navajo word for this tree is c’ó deniní, which roughly translates to “it’s a sharp spruce.”
These trees have also started falling out of favor for use as Christmas trees because of those sharp needles.
Just something to keep in mind when selecting a new home for one in your landscape.
As mentioned earlier, the pollen can be messy in spring. That’s another good reason to keep the tree away from patios, entryways, or frequently used walkways.
Climate
Colorado blue spruce thrives in cool, dry climates. It has excellent cold tolerance, capable of surviving temperatures as low as -40°F.
On the other hand, it doesn’t handle extreme heat very well. If temperatures regularly rise above 80°F and the humidity is high, your spruce is likely to suffer.
Heat combined with humidity is a quick blue spruce killer.
Yes, this tree grows in hot regions, but in nature it grows in high elevation canyon bottoms where it tends to be cooler and there’s more water available.
Light
Colorado blue spruce trees do best in full sun, though a few hours of shade is fine.
A little shade in the afternoon is preferable if you live somewhere that becomes very hot during the summer. The best color appears when the tree is grown in bright sun.
Soil
To help your blue spruce to thrive, pick a spot in the garden with organically-rich, loose, moist soil.
Because the root system is extensive and deep, trying to amend your soil won’t do much good in the long run.
Instead, it’s better to choose a spot with naturally good conditions rather than trying to fix poor soil.
Blue spruces are adaptable, so they will be fine in slightly sandy or clay soil, but heavy clay or extremely sandy soil is a no-go.
Water
Though this is a drought-tolerant species that survives in arid regions, you’ll most often find growing wild near sources of water like streams or lakes.
This tells us that the species is adaptable. Blue spruce prefers a moist spot, but it can get by on less, so long as the soil is well-draining.
Avoid planting in areas with soggy or standing water. When the tree is young, keep the soil evenly moist but not wet.
Once established, you can reduce watering. Mature trees won’t need supplemental water except during extended periods of drought.
Cultivars to Select
Visit just about any nursery and you’re likely to find several blue spruce cultivars available as well as the species plant.
On that note, if you want to grow the species, you can find plants available at Fast Growing Trees.
Here are a few standout cultivars to consider:
Baby Blue
‘Baby Blue’ has everything you love about a Colorado blue spruce in a petite, semi-dwarf package. It tops out at just 15 to 25 feet tall and up to 15 feet wide.
This cultivar maintains the classic pyramidal shape and features extremely vivid needles that are even bluer than those of the species.
You can find ‘Baby Blue’ plants available from Fast Growing Trees.
Blue Wonder
If your main interest is the distinctive color of a Colorado blue spruce, then ‘Blue Wonder’ should be at the top of your list.
It shares all the typical characteristics of the species, though it tends to stay a bit smaller.
This cultivar has bright gray-blue needles that are especially vibrant and guaranteed to stand out in the landscape.
You can find ‘Blue Wonder’ available at Fast Growing Trees.
Baker’s
Baker’s blue spruce (P. pungens var. glauca ‘Bakeri’) has more of a columnar shape than your typical spruce and it’s also far more petite.
Perfect for a smaller landscape, this one will mature to a perfectly manageable 30 feet tall and just 15 feet wide.
Grower R. Ellery Baker of Hiti Nurseries in Pomfret, Connecticut discovered this seedling in Massachusetts in the late 1920s and developed it for commercial release in 1933.
Want one? Nature Hills Nursery has this beauty in #5 containers.
Fastigiata
‘Fastigiata’ is a semi-dwarf cultivar with an upright, columnar growth habit that gradually tapers through the top third of the tree, giving it a somewhat pyramidal silhouette.
It typically grows up to 15 feet tall and about five feet wide, making it a smart choice for narrow spaces in the garden. Just be sure to give it enough room to reach its mature size.
The needles tend to retain their blue color more reliably than many other cultivars, and certainly more consistently than the species. It’s also hardier than most, withstanding conditions as cold as USDA Zone 2.
While the exact origin is unclear, ‘Fastigiata’ has been available in Canada since 1989 and the U.S. since 1993.
Fat Albert
The well-respected Iseli Nursery in Boring, Oregon – renowned for breeding unique and interesting conifers – is credited with introducing ‘Fat Albert’ in the 1970s.
Founder Jean Iseli said that he found the natural hybrid in a field of seedlings, and he was clearly onto something!
Despite the name, ‘Fat Albert’ isn’t particularly wide. It reaches up to 45 feet tall and 20 feet wide at most. The name is a nod to the popular cartoon character, not its shape.
This cultivar features that perfect pyramidal shape and striking silver foliage.
It’s particularly slow growing and long lived, so it can be a highlight in your garden for decades (even centuries) to come.
If you want a tried-and-true option with the perfect shape, bring home ‘Fat Albert’ from Fast Growing Trees.
Globe
For a truly dwarf option, there’s nothing better than the glorious Globe (Picea pungens var. glauca ‘Globosa’).
This compact cultivar reaches just five feet tall and six feet wide at maturity, with a naturally rounded shape that requires no pruning to maintain.
It’s one of those set-it-and-forget-it plants you can enjoy for years without lifting a finger.
Bred by Luis’ Nursery in Boskoop, Holland, in 1937, it was later refined and introduced by Le Feber & Company in 1955.
Clearly, they were onto a hit as this cultivar has become the go-to choice for gardeners wanting a dwarf blue spruce, especially one with a bushy, compact habit.
If that sounds like you, visit Fast Growing Trees where you can find plants available in five-gallon pots.
Slenderina
So far, we’ve talked about upright spruce and one cute little shrub. But I’m a total sucker for a weeping tree, so I’d be remiss to skip the lovely ‘Slenderina.’
I have grown this gorgeous weeper in several of my gardens and it is always the one that draws stares and comments.
‘Slenderina’ grows to about 15 feet tall and about half as wide, with pendulous, weeping branches that can also twist and turn as they emerge from the central trunk.
You can even train the main trunk itself to curve and twist, too. I once saw one trained into a half arch as the entrance to a wisteria tunnel and it was magnificent!
You can find ‘Slenderina’ available at Nature Hills Nursery.
Maintenance
You don’t need to prune a Colorado blue spruce regularly.
The only time you’ll need to bring out the pruners is if a branch dies, is damaged by pests, or doesn’t fit the overall shape you’re aiming for.
The best time to prune is in late winter while the tree is still dormant – just avoid doing so when temperatures are below freezing.
Use loppers, a saw, or hand pruners to remove unwanted branches. Cut as close as possible to the adjoining branch or trunk.
There’s no need to seal the wound, the tree will do that on its own with the sticky resin common to spruces, pines, and firs.
Learn more about pruning conifers here.
Fertilizing is typically unnecessary unless your young tree appears stunted or unhealthy.
In that case, start with a soil test to determine if there are any deficiencies and feed according to the test results.
Your local university extension office is an excellent resource for soil testing kits and region-specific recommendations.
Propagation
You can’t reproduce blue spruces through layering, but you can grow them from seed. The easiest way to get started is to purchase a plant from a nursery for transplanting.
These are slow-growing trees and if you start one from seed, it can take decades for it to reach its mature size.
From Seed
Propagating any evergreen from seed tends to be a slow process, so if you want to use this method you’ll need to exercise some patience.
We have a guide to growing pines from seed, and the process is the same. Here are the basic steps:
- Start by harvesting a mature cone that hasn’t yet released its seeds. It should be buff-colored with closed scales, though you’ll notice small cracks between them – that means they’re close to opening.
- Next, stratify the seeds for several months in moist sand to mimic natural winter conditions.
- In late winter or early spring, sow the seeds in pots filled with a well-draining potting mix. Keep the soil consistently moist during this stage.
When the seedlings are a few inches tall, they’re ready to be transplanted into the garden or a larger container.
Transplanting
To transplant a seedling you grew yourself or a plant you purchased from the nursery, the first step is to choose your location.
Dig a hole that is just a bit deeper and at least twice as wide as the growing container. I like to make a generously-sized hole to allow the young roots to spread out and become established.
Remove the plant from its container and gently loosen up the roots. If the plant is particularly rootbound, you can soak the root ball for an hour or so in water to help loosen it up.
Spread the roots outward and away from the trunk, then place the plant in the hole. Backfill with the soil you removed and water thoroughly.
Keep the soil moist like a well-wrung-out sponge for the first few years. When the plant is established, you won’t need to water at all unless there’s an extended dry spell.
Pests and Disease
The stiff, spiky needles are pretty unattractive to herbivores, and Colorado blue spruce trees are almost disease-free.
But that doesn’t mean they’re entirely problem-free, pests can still show up from time to time.
Aphids
Aphids are the most common culprits, particularly the spruce aphid (Elatobium abietinum).
These pests can strip the needles of their signature gray-blue hue, turn them yellow, or even cause them to drop entirely.
A single infestation may not be a big deal, but repeated infestations over multiple years can weaken and eventually kill a tree.
If your spruce is looking sparse or the older foliage is yellowing and falling off, get in close and check for tiny aphids.
Populations typically swell in the spring, though the damage might not show until summer, by then, it’s too late to prevent it.
Start managing them in fall and again in early spring with the appropriate treatment.
You can learn more about how to deal with aphids here.
Scale
Scale insects are less common but still a concern. The most likely offenders are spruce-bud scale (Physokermes piceae) or blackpine scale (Nuclaspis californica).
While the species may vary, the treatment approach is largely the same.
Check out our guide to scale insects for help managing an infestation.
Western Spruce Budworm
Another serious pest in the tree’s native range and up through the Pacific Northwest is the western spruce budworm (Choristoneura freemani).
Repeated infestations can kill trees. The adult is a moth with gray, brown, and orange wings marked with a single white dot. The wings are about an inch wide and half an inch long when fully extended.
In spring, females lay eggs on the undersides of needles. The larvae hatch as yellow-green caterpillars with brown heads, eventually developing reddish-brown bodies with black heads and growing over an inch long.
Young larvae don’t feed right away. Instead, they wiggle into soft parts of the tree like new buds or tender needles and spin silky webs as shelter.
Then they begin feeding, targeting developing foliage and cones. Their feeding kills affected areas, and young shoots may emerge twisted or deformed.
Fortunately, natural predators like native parasitic wasps and flies, birds, rodents, and small herbivores often keep populations in check.
But if you spot budworms on your spruce, don’t wait for beneficial insects to take care of the problem.
Use a product containing Bacillus thuringiensis kurstaki (Btk), a beneficial bacterium that targets insects in the order Lepidoptera including budworms, without harming bees, beetles, or flies.
Bonide’s Thuricde uses Btk and you can find this product available at Arbico Organics ready-to-use or as concentrate.
Spray every week from early summer until the fall or until no new damage symptoms develop.
Don’t Be Blue… or Do!
Blue isn’t a common color in the plant world. Green is everywhere, and even red and yellow show up regularly. But blue? Not so much.
That’s only one of the reasons that this tree is such an incredible standout. In a sea of green, it’s a beacon of color.
But even if it were green, I still think it would be eye-catching. That classic Christmas tree shape is pretty cool, but even the weeping and bushy types are fantastic.
So, what appeals to you about this unique evergreen? Is it the color, the ease of care, the shape, or all of the above? Let us know in the comments section below!
And for more information about growing conifers in your landscape, add these guides to your reading list next:
