Spruce trees’ full-bodied and continually green-blue color are of high value in Denver. That, plus their hardiness 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 with these spruce tree care tips.
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:
On its branches, needles of a spruce tree attach individually, rather than growing in clusters. You can roll them gently between your fingers and feel their flexible four sides.
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.
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. Branches are upturned and grow in a making the spruce a full and bushy shape.
Spruce Tree Species Commonly Found In Denver
Spruce trees are a part of the Pinaceae Evergreen Tree family and 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 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 ft 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 popular 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 even makes a great Christmas tree!
With dark green to blue-green needles and 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 is best grown in moist and 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. Because of its fantastic year-round color and outstanding pyramidal shape we recommend you use it as an ornamental tree. Thick, dense needles and a strong central leader give the Blue Spruce an excellent form.
The Colorado Blue Spruce grows at a medium rate to a height of 50–75 ft and a spread of 10–20 ft at maturity. It can also tolerate Denver’s acidic soil and mild flooding and drought.
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:
IPS Beetles, also known as an engraver beetle, are dark, reddish-brown or black colored and feed on the phloem of wood. They mark and carve the wood as they feed, hence the name engraver beetle. Only about 1/8 to 3/8 in long, they are small as individual insects.
Truly, the growing number of IPS beetles in Denver is concerning. Presently, there are eleven species native to the area. IPS beetles are spreading more rapidly than other pests because they can withstand the cold winter temperatures and have 2-4 generations per year. The beetles are active from early March all the way through November.
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. Occasionally, they become rust-colored on the tree.
Needles drop from branches when the tree is 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.
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 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 or exposed roots, such as through damage from a lawnmower. 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
- branch die-back that spirals ups the crown
Year-old needles cast after turning rust colored in the spring. Blue spruce is very susceptible to this fungal disease, as are black and white spruce.
Spruce tree care may sometimes include destroying 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 1.5 inches long and again 3 weeks later to protect young needles from infections that occur in late spring and early summer.
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 1.5 inches long and again three 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 Care And Treatment Options
Healthy spruce trees can fight off disease, infection, and infestation. Keeping up with spruce 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.
- 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: Our arborists recommend trunk injection treatments and crown sprays as preventative methods, regardless of species and size. Pest prevention and control helps your spruce trees maintain their signature vibrant blue-green color. Chemical treatments such as insecticides are especially important in combating the IPS beetle infestation ravaging the Denver metro region. It needs to be controlled or homeowners are going to lose their prized possessions. These destructive pests require a proactive approach in order to save evergreen trees in our state.
Visit the rest of our website to learn more about spruce tree care or to schedule your complimentary on-site diagnosis. 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.