Hackberry (Celtis occidentalis) is one of the few trees that are native to the state of Colorado. This tree’s ability to resist drought and adjust to fluctuating temperatures makes it a perfect Denver resident.
The hackberry tree’s popularity stems from its size and shape, which turn it into an excellent shade plant. Since its seeds germinate easily, they spread quickly and often interfere with flower and shrub growth.
Appearance
Hackberry trees grow to be 40–60 feet, with a spread of 40–50 feet. They have a distinctive grayish-brown bark with corky ridges. The crescent-shaped leaves are 2–5 inches long, with serrated edges and an asymmetrical base. They turn yellow in the fall.
Flowering occurs in late April and early May. The tree produces small greenish flowers, which aren’t always easy to notice from the ground. By late summer to fall, the tree bears berry-like fruit that starts out as orange-red and then turns dark purple.
Why Hackberry Thrives in Denver
The hackberry tree grows throughout Colorado, especially in urban areas and along riverbanks. Since the tree is highly adaptable, it thrives in various soils, including clay and limestone.
Hackberry is highly drought resilient, which is perfect for Colorado’s semi-arid climate. While hackberry is adaptable, it still grows best in areas where it gets at least 6 hours of sunlight daily. It also prefers well-drained and organically rich soil with a pH of not more than 8.0.
Hackberries are valued for their shade, erosion control, and resistance to urban stressors such as pollution and compacted soils. They are also relatively pest-resistant. However, they can be affected by hackberry nipple gall, caused by Pachypsylla psyllids.
Elevation and Temperatures
Hackberries struggle to grow above 6,500–7,000 feet because they are not well-adapted to the harsher winter conditions of higher elevations. While some isolated trees may survive in protected valleys or warm microclimates at slightly higher elevations, they are uncommon in mountainous regions.
This tree can tolerate winter lows of 0°F to 20°F. However, when faced with high-altitude environments, hackberries grow much slower. They require at least 120 frost-free days to establish and thrive. That’s why lower elevations with longer growing seasons suit these trees better.
In Colorado, hackberry trees naturally occur along riverbanks and canyons in the eastern plains and foothills but rarely extend into high-altitude forests.
Interesting Facts about Hackberry Trees
Hackberry trees aren’t just aesthetically appealing shade providers. They can surprise you with some interesting qualities.
Regeneration Abilities
Just like all other trees, hackberry is susceptible to fire damage. However, once the danger passes, this tree regenerates very quickly.
Impressive Lifespan
Hackberry trees can live as long as 150 to 200 years. The key to their longevity is the right environment. The tree is vulnerable to poor conditions when it’s young. However, once established it becomes highly tolerant and adaptable.
Popular Fruit
Fruits produced by hackberry trees are a favorite food for birds like cedar waxwings, robins, and mockingbirds. These fruits can persist on the tree into winter. They rarely fall to the ground because birds usually get to them first.
Long History
Indigenous tribes ground hackberry fruits into a paste for energy-rich food. They also used various parts of the tree for medicinal purposes, for example, to treat sore throats and indigestion.
Impressive Family Ties
Surprisingly, hackberry trees belong to the Cannabaceae family. It means they are distant relatives of both hemp (Cannabis sativa) and hops (Humulus lupulus), which are used in brewing beer.
For more information about hackberry trees, contact our certified arborists today.