Dense, bright green pine trees are sought after in Denver for several purposes. Their vibrant color and ability to thrive in adverse conditions make them a top choice for residential gardens and public spaces. Learn how to identify different pine tree varieties and how to help them grow strong and healthy!
Pine Tree Species Commonly Found In Denver
Part of the Pinaceae Pinus tree family, there are believed to be 126 species of pine trees in total. Denver is home to a handful of these hardy and attractive conifer trees. Each pine species is distinct, even though they share some fundamental similarities. Learn more about each species and see if you can identify them the next time you’re out on a hike!
Bristlecone pines are famous for being the oldest living tree species! Adaptable to many climates, they grow well in zones 3-7 and even thrive in acidic soil. They prefer full sun and under ideal conditions, they’ll grow 20-60 ft tall and spread 15-20 ft wide. Thanks to their dense wood, Bristlecone pines can fend off attacks from harmful pests and fungi. This variety is also hardy during drought conditions and makes a great patio or garden accent tree.
Found in zones 4-7, this fast-growing pine species is highly drought-resistant and tolerant of many soils. Limber pines prefer well-drained soil and can thrive in rocky soil, making them a strong choice for natural plantings. It’s dense blue-green needles form an attractive pyramid shape. This hardy species is often sought after for its ability to resist disease and pests. At maturity, it only grows to 20 or 30 ft, making it a great option for a garden or screening.
When it is young, the lodgepole pine makes an excellent ornamental tree. Its yellow-green needles and flaky orange bark are unique and attractive. As it ages, it grows in a rounded shape, reaching 70–80 ft tall and 20 ft wide at maturity. The Lodgepole pine can thrive in acidic, loamy, moist, and even clay soils. It prefers full to partial sun and grows at a medium rate.
Adding 12 inches of height or more each year, the Ponderosa pine quickly grows to stand between 60 and 125 feet tall at maturity. This species features an orange-brown bark that grows in patterned rough rectangular plates. The tree has an overall narrow conical shape and attractive rugged appearance. Of all the pine varieties, it is most resistant to salt-spray and has few issues with disease or pests. Although it is low maintenance, this pine needs room to grow and should not be planted in a crowded garden area. Its trunk alone can span 4ft when fully mature! For best results, plant in full sun and well-drained soil.
Native to the southwestern United States, the Pinyon pine is a slow-growing but long-living variety. Dense and compact, this soft bushy tree grows only to 10 or 20 ft, so it won’t crowd out other plants or shrubs. Its cones produce edible nuts that are tasty raw or toasted! Drought resistant and tolerant of many soils, Pinyon pines work well in rock gardens and xeriscaping.
Standing 30′ to 50′ tall, and spread almost as wide, at maturity, the Scotch pine has a unique conical shape. It’s branches spread horizontally with age, giving it a flattering full shape and making it an ideal Christmas tree. The average lifespan of a Scotch pine is typically 150–300 years! This variety tolerates many soil types and climates, prefers full sun, and can be transplanted with ease. It’s an ideal choice for tough sites and makes an excellent shade or screen tree.
How to Identify Pine Trees
Wondering what’s the difference between a fir and a pine tree? You can do a quick check in the yard following these easy steps. Pine tree identification typically depends on three things: the cones, bark, and the way the needles are clustered.
Needles: Pine tree leaves are called needles because they’re long and thin in shape. If you look closely, you’ll see they grow in a spiral out of the twigs stemming from larger branches. These spirals are called “candles” and they fall from the tree after about two years. If you feel the needles, you will see that they have a waxy protective outer layer. This layer helps the pine withstand drought and prevents it from catching fire.
Bark: Pine bark is usually rough to the touch and thick, which helps it defend itself from pests. It is typically reddish-brown in color, with grey or black edges.
Cones: Pine trees produce both male and female cones. The female cone is chubby, with thick woody petals growing from the center outwards. Male pine cones are formed in a tighter cylinder shape and hold pollen that will fertilize the female pinecone.
Pine Tree Disease
Pine trees are primarily plagued by just one major disease in the Denver area, Pine Wilt disease. Find out what causes Pine Wilt in Denver and how to spot the first signs of disease with details in this guide from Colorado State Univeristy Extension:
Pine Wilt disease
- Pine wilt is a lethal disease caused by a native nematode, vectored to trees by a wood borer insect–the pine sawyer beetle.
- Exotic pines, including Scots, Austrian, and mugo, are susceptible to infection by the nematode. Native pines are not susceptible to this pathogen.
- High summer temperatures are required for the nematode to develop in the beetle and within infested trees.
- The disease is now a threat in both eastern and western Colorado. It can be prevented by timely sanitation and chemical injections.
- Native ponderosa, limber, bristlecone, and lodgepole pines are normally not susceptible to the disease. They have built up a resistance to the nematode, but that resistance can be compromised by periods of drought.
- Pine wilt is a lethal disease of the widely planted Scots, Austrian and mugo pines.
- Infection usually starts in June or July but visible symptoms won’t appear until early fall.
- When nematodes attack susceptible trees, they feed on the epithelial cells of resin ducts and move systemically throughout the sapwood of the branches, trunk, and roots. This causes physical changes within the tree resulting in water blockage, wilting and death.
- Needles to initially turn grayish turn from gray-green to tan and eventually brown due to lack of water.
- Dead needles remain attached to the tree through the winter.
- Diseased wood is very dry to the touch as the infection process interferes with resin production.
- Infected trees also develop a blue stain in the wood.
- On Scots pine, the entire tree usually wilts and dies within a few months.
Pine Tree Infestation
Pine wilt is a serious problem, but pest infestation should not be overlooked. Pine trees in Denver are especially susceptible to the Mountain Pine Beetle. Keep an eye out for possible pest attacks by looking for these signs described by the Colorado State University Extension:
Mountain Pine Beetle
- Mountain pine beetles (MPB) are the most important insect pest of Colorado’s pine forests. MPB often kill large numbers of trees annually during outbreaks.
- Trees that are not growing vigorously due to old age, crowding, poor growing conditions, drought, fire or mechanical damage, root disease and other causes are most likely to be attacked.
- For a long-term remedy, thin susceptible stands. Leave well-spaced, healthy trees.
- For short-term controls, spray, cover, burn or peel attacked trees to kill the beetles. Preventive sprays can protect green, unattacked trees.
- Mountain pine beetles develop in pines, particularly ponderosa, lodgepole, Scotch and limber pine.
- Bristlecone and pinyon pine are less commonly attacked.
- During the early stages of an outbreak, attacks are limited mainly to trees under stress from injury, poor site conditions, or root disease.
- Popcorn-shaped masses of resin, called “pitch tubes,” on the trunk where beetle tunneling begins. Pitch tubes may be brown, pink or white.
- Boring dust in bark crevices and on the ground.
- Evidence of woodpecker feeding on the trunk.
- Needles turning yellowish to reddish throughout the entire tree crown.
- Presence of live MPB as well as galleries under the bark. This is the most certain indicator of an infestation. A hatchet for removal of bark is needed to check trees correctly.
- Blue-stained sapwood in the tree trunk.
Pine Tree Care And Treatment Options
Strong and healthy pine trees can fight off Pine Wilt disease and Mountain Pine beetle 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 pine trees thrive:
- Watering: Proper watering is an overlooked but very important tree care practice. Pine species prefer well-drained soil and can become compromised if their soil becomes too saturated with water. We can provide expert consultation on how much water you should be giving your pine trees, and how often.
- Fertilization: Pine trees are known for adapting to different soil types, but even the ones commonly found in Denver, can struggle in the high-alkaline soil. 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 pine 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: Pine trees can be proactively protected from the Mountain Pine beetle with the correct spray application. Spraying can also help an infected tree if the infestation is recognized early on. Pest control helps your pine trees maintain their signature vibrant blue-green color and lengthens their life-span.
- Bactistat: trunk injections are an effective proactive measure to prevent Pine Wilt disease. Trained arborists can administer this application in spring before the spread and onset of the disease during the summer months.
If you are concerned that your pine 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! Keep your pine trees strong and healthy by building a custom care plan with one of our trained arborists.