Full-bodied, continually green-blue spruce trees are valued in Denver for many purposes. Their hardiness, vibrant color, and sturdy shape make them a go-to choice for residential and community landscapes. Learn how to identify different spruce varieties and how to help them grow strong and healthy!
Spruce Tree Species Commonly Found In Denver
Part of the Pinaceae evergreen tree family, there are 35 spruce species in total. Denver is home to five of these large, conifer tree varieties. Although they share some basic similarities, each spruce species is unique. Learn more about the different varieties and see if you can spot them apart on your next bike ride around Denver!
This green short-needled spruce grows in a columnar fashion, making it a great choice for a vertical accent. The fastest growing of all spruce varieties, the Norway Spruce stands about 40–60′ ft tall and 25–30 ft wide when fully developed. It prefers full sun and will tolerate acidic, loamy, moist, sandy, well-drained and clay soils. The Norway spruce is useful as a windbreaker and can withstand snow loads, but limbs are known to sag and droop with age.
A Christmas tree favorite, the White spruce has curved, pale green needles and hanging cones. This hardy variety grows well in urban and rural areas and will tolerate wind, heat, cold, drought, crowding and some shade. The White spruce can thrive in Denver’s alkaline soil, growing to 40–60′ ft tall and 10–20′ wide at maturity. Its seeds will attract wildlife like crossbills, evening grosbeaks, and red-breasted nuthatches to your yard.
Black Hills Spruce
The Black Hills spruce is sought after for its ability to resist winter injury and drought damage. Its hardiness and conical shape make it ideal for use as a windbreak/shelterbelt, privacy screen, and accent planting. It is even used regularly as a Christmas tree! With dark green to blue-green needles brown cylindrical cones, the Black Hills spruce grows slowly to stand 30–60’ ft tall and 15–25′ ft wide. Due to its shallow root system, it cannot handle flooding and is highly sensitive to soil compaction.
Commonly planted as an ornamental evergreen, this variety is native to the Rocky Mountains. The Colorado spruce grows best in moist, acidic soils that are well-drained. Its hardy nature helps it tolerate conditions such as urban pollution and drought. In full sun it grows at a medium rate to stand upright, approximately 50 ft tall at maturity.
Colorado Blue Spruce
With brilliantly bright blue needles, the variety stands out in the landscape. It is regularly used as an ornamental tree due to its fantastic year-round color and outstanding pyramidal shape. Thick, dense needles and a strong central leader give the Blue Spruce excellent form. The Colorado blue spruce grows at a medium rate to a height of 50–75′ and a spread of 10–20′ at maturity. It can also tolerate Denver’s acidic soil and mild flooding and drought.
How to Identify Spruce Trees
Wondering if you have any spruce trees on your property? You can do a quick check in the yard following this easy three-step guide:
Leaf: On its branches, needles of a spruce tree are attached individually rather than growing in clusters. You can roll them gently between your fingers and feel their flexible four sides.
Cone: Spruce cones are flexible and bend easily. Their smooth, thin scales, make their texture unique. This sets them apart from traditional pine cones that have rough, thick, inflexible scales.
Form: Spruce needles sprout and grow from small pegs on the branches. After dead needles fall off the tree, these pegs remain, giving the branches a noticeably rough texture. The pegs appear to dot the surface of each branch. The branches themselves are upturned and grow in such a way that gives the spruce a full and bushy shape.
Spruce Tree Diseases
Spruce trees suffer from a variety of fungal diseases on the Colorado front range. Find out what kind of threats spruce trees are up against in Denver and how to spot the first signs of disease with details in this guide from Penn State Extension:
This fungal disease can cause serious damage to your cottonwoods. The Leucostoma kunzei fungus enters the tree through stressed or injured openings in the bark. As the fungus spreads, sunken cankers form. If left untreated, the cankers eventually girdle the branches, restricting the flow of water and nutrients, and killing that area of the tree. This disease is slow to develop. Be on the lookout for signs of infection:
- cracked, dry or discolored cankers
- sunken, discolored bark
- oozing resin
Year-old needles are cast after turning rust colored in the spring. Blue spruce is very susceptible to this fungal disease, as are black and white spruce.
Destroy heavily infected trees. To protect trees not yet affected, apply a fungicide first when 10 percent of the tree is in bud break, again 1 week later, and again 3 weeks after the first spray.
Year-old needles turn lavender in color and have tiny, black fungal fruiting structures in rows on either side of the midvein on the underside of the needle. Large bare areas develop on the tree as needles fall.
Control proper air circulation around the tree by spacing trees strategically and removing weeds. Apply a fungicide when new shoots are 1½ inches long and again 3 weeks later to protect young needles from infections that occur in late spring and early summer.
Stigmina Needle Blight
Year-old needles turn yellow, brown and then fall in the Spring a year after infection. Brown needles have tiny, black fungal fruiting structures in rows on either side of the midvein on the underside of the needle. Large bare areas develop on the tree as needles fall while the new, current year’s needles appear healthy. The dark fruiting structures sometimes appear to have fuzzy tops.
Space trees and provide good weed control to ensure free air circulation around the tree. Apply a fungicide when new shoots are 1½ inches long and again 3 weeks later to protect young needles from infections that occur in May through June. For best control, apply the fungicide three consecutive years.
Spruce Tree Infestations
Not only are spruce trees plagued by disease, but they are also susceptible to pest infestation. Keep an eye out for possible pest attacks by looking for these signs described by the Colorado State Forest Service:
These native bark beetles typically infest Colorado and Blue spruce trees. Needles on infested trees may turn a pale yellowish-green color and tend to drop to the ground after high winds, but rarely turn rust colored on the tree. Needles typically drop from branches the second summer after the tree has been infested. Boring dust, produced when beetles bore new entry holes, may accumulate in bark crevices and around the base of the tree. Streams of resin along the main trunk are often associated with recently attacked trees.
Preventive insecticide sprays may prove effective in preventing spruce beetle infestation. Certain formulations of pyrethroids that are registered and tested for effectiveness are the primary preventive insecticidal sprays used to help reduce the likelihood of attacks on individual trees. The Colorado State Forest Service (CSFS) recommends spraying only high-value trees, such as those near homes, businesses or recreation sites. Follow the label of any chosen product.
These tiny insects harm spruce trees by feeding on shoots and sucking the plant sap. In doing so, they cause the shoots to deform and produce galls that resemble cones. The damage from gall adelgids is mainly cosmetic and can be controlled proactively with an insecticide.
Spruce Spider Mites
Damage caused by spruce spider mites is often mistaken for needle cast disease because the main visible symptom is discoloration and eventually dead needles. Not all insecticides will control mites. Consult with an arborist for treatment and pest management options.
Spruce Tree Care And Treatment Options
Healthy spruce trees can fight off disease, infection, and infestation. Keeping up with tree care is an important investment in your tree’s longevity. Here are our top recommendations for annual care that will help your spruce trees thrive:
- Watering: proper watering is an overlooked but very important tree care practice. Some spruce species are prone to fungi related diseases if their soil becomes too saturated with water. They need the soil to be drained regularly. We can provide expert consultation on how much water you should be giving your spruce trees, and how often.
- Fertilization: for many spruce trees, even the ones commonly found in Denver, the high alkaline soil can lead to problems. The best way to neutralize this threat is with the right fertilizer application. Balancing the soil and getting your trees the nutrients they crave will keep them strong and healthy.
- Tree trimming: annual pruning and trimming help spruce trees keep their beautiful shape. It’s also a good opportunity to check and trim away any parts of the tree suffering from infection or pests.
- Insecticides: although spruce trees are not preyed on by destructive pests like the EAB, an insecticide may still be applicable for large infestations of spruce beetles or gall adelgids. Pest control helps your spruce trees maintain their signature vibrant blue-green color.
If you are concerned that your spruce tree is showing signs of disease or infestation, contact one of our certified arborists immediately! At Fielding Tree & Shrub Care we take a four-step approach for treating spruce trees:
- Step 1: A complimentary on-site disease diagnosis of your trees and/or shrubs. Sending a picture in advance helps speed things up!
- Step 2: We work to cure the disease or at least slow it down with the most viable treatment option available for your tree or shrub’s unique situation.
- Step 3: A proactive approach is implemented to protect your existing trees from disease or infestation.
- Step 4: Unfortunately, sometimes trees and shrubs die, even with our best, safest, and most proven treatment solutions. If your tree or shrub dies, we try to remove the dead plant as soon as reasonably possible. This keeps your property safe from unnecessary infestations and unsightly rotting trees or shrubs.
To learn more, schedule your complimentary on-site diagnosis today! One of our arbor experts will walk you through our four-step approach for treating spruce trees and create a custom plan for the unique needs of your trees!